docs: add version placeholders for new features

Update Title FAQ based on latest info

.changeset/clean-wolves-turn.md

@@ -0,0 +1,5 @@
+---
+'mermaid': patch
+---
+
+fix: Render newlines as spaces in class diagrams

.changeset/loud-results-melt.md

@@ -0,0 +1,5 @@
+---
+'mermaid': minor
+---
+
+feat: Add half-arrowheads (solid & stick) and central connection support

.changeset/tough-clocks-flow.md

@@ -1,5 +0,0 @@
----
-'mermaid': minor
----
-
-feat: Add support for aggregation relationships in ER diagram

cypress/integration/rendering/classDiagram.spec.js

@@ -524,5 +524,18 @@ describe('Class diagram', () => {
       `,
       {}
     );
+    it('should handle an empty class body with empty braces', () => {
+      imgSnapshotTest(
+        ` classDiagram
+        class FooBase~T~ {}
+    class Bar {
+        +Zip
+        +Zap()
+    }
+    FooBase <|-- Ba
+        `,
+        { flowchart: { defaultRenderer: 'elk' } }
+      );
+    });
   });
 });

cypress/integration/rendering/erDiagram.spec.js

@@ -369,94 +369,4 @@ ORDER ||--|{ LINE-ITEM : contains
       );
     });
   });
-
-  describe('Aggregation Relationships', () => {
-    it('should render basic aggregation relationships', () => {
-      imgSnapshotTest(
-        `
-        erDiagram
-          DEPARTMENT <> EMPLOYEE : contains
-          PROJECT <>.. TASK : manages
-          TEAM <> MEMBER : consists_of
-        `,
-        { logLevel: 1 }
-      );
-    });
-
-    it('should render aggregation with entity attributes', () => {
-      imgSnapshotTest(
-        `
-        erDiagram
-          DEPARTMENT <> EMPLOYEE : contains
-          DEPARTMENT {
-            int id PK
-            string name
-            string location
-          }
-          EMPLOYEE {
-            int id PK
-            string name
-            int department_id FK
-          }
-        `,
-        { logLevel: 1 }
-      );
-    });
-
-    it('should render aggregation with quoted labels', () => {
-      imgSnapshotTest(
-        `
-        erDiagram
-          UNIVERSITY <> COLLEGE : "has multiple"
-          COLLEGE <> DEPARTMENT : "contains"
-          DEPARTMENT <> FACULTY : "employs"
-        `,
-        { logLevel: 1 }
-      );
-    });
-
-    it('should render mixed relationship types', () => {
-      imgSnapshotTest(
-        `
-        erDiagram
-          CUSTOMER ||--o{ ORDER : places
-          ORDER ||--|{ ORDER_ITEM : contains
-          PRODUCT <> ORDER_ITEM : "aggregated in"
-          WAREHOUSE <>.. PRODUCT : "stores"
-        `,
-        { logLevel: 1 }
-      );
-    });
-
-    it('should render aggregation with entity aliases', () => {
-      imgSnapshotTest(
-        `
-       erDiagram
-         d[DEPARTMENT]
-         e[EMPLOYEE]
-         p[PROJECT]
-         t[TASK]
-
-         d <> e : contains
-         p <>.. t : manages
-
-        `,
-        { logLevel: 1 }
-      );
-    });
-
-    it('should render complex aggregation scenarios', () => {
-      imgSnapshotTest(
-        `
-        erDiagram
-          COMPANY <> DEPARTMENT : owns
-          DEPARTMENT <> EMPLOYEE : contains
-          EMPLOYEE <> PROJECT : works_on
-          PROJECT <> TASK : consists_of
-          TASK <> SUBTASK : includes
-        `,
-        { logLevel: 1 }
-      );
-    });
-  });
 });

cypress/integration/rendering/sequencediagram-v2.spec.js

@@ -655,5 +655,126 @@ describe('Sequence Diagram Special Cases', () => {
         expect(svg).to.not.have.attr('style');
       });
     });
+
+    describe('Central Connection Rendering Tests', () => {
+      it('should render central connection circles on actor vertical lines', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Central connection
+        Bob ()-->> Charlie: Reverse central connection
+        Charlie ()<<-->>() Alice: Dual central connection`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with different arrow types', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()->>() Bob: Solid open arrow
+        Alice ()-->>() Bob: Dotted open arrow
+        Alice ()-x() Bob: Solid cross
+        Alice ()--x() Bob: Dotted cross
+        Alice ()->() Bob: Solid arrow`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with bidirectional arrows', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()<<->>() Bob: Bidirectional solid
+        Alice ()<<-->>() Bob: Bidirectional dotted`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with activations', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Activate Bob
+        activate Bob
+        Bob ()-->> Charlie: Message to Charlie
+        Bob ()->>() Alice: Response to Alice
+        deactivate Bob`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections mixed with normal messages', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ->> Bob: Normal message
+        Bob ()->>() Charlie: Central connection
+        Charlie -->> Alice: Normal dotted message
+        Alice ()<<-->>() Bob: Dual central connection
+        Bob -x Charlie: Normal cross message`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with notes', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Central connection
+        Note over Alice,Bob: Central connection note
+        Bob ()-->> Charlie: Reverse central connection
+        Note right of Charlie: Response note
+        Charlie ()<<-->>() Alice: Dual central connection`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with loops and alternatives', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        loop Every minute
+            Alice ()->>() Bob: Central heartbeat
+            Bob ()-->> Charlie: Forward heartbeat
+        end
+        alt Success
+            Charlie ()<<-->>() Alice: Success response
+        else Failure
+            Charlie ()-x() Alice: Failure response
+        end`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with different participant types', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant Alice
+          actor Bob
+          participant Charlie@{"type":"boundary"}
+          participant David@{"type":"control"}
+          participant Eve@{"type":"entity"}
+          Alice ()->>() Bob: To actor
+          Bob ()-->> Charlie: To boundary
+          Charlie ()->>() David: To control
+          David ()<<-->>() Eve: To entity
+          Eve ()-x() Alice: Back to participant`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+    });
   });
 });

cypress/integration/rendering/sequencediagram.spec.js

@@ -1053,4 +1053,167 @@ describe('Sequence diagram', () => {
       ]);
     });
   });
+  describe('render new arrow type', () => {
+    it('should render Solid half arrow top', () => {
+      imgSnapshotTest(
+        `
+    sequenceDiagram
+      Alice -|\\  John: Hello John, how are you? 
+      Alice-|\\  John: Hi Alice, I can hear you!
+      Alice -|\\  John: Test
+      `
+      );
+    });
+    it('should render Solid half arrow bottom', () => {
+      imgSnapshotTest(
+        `
+    sequenceDiagram
+      Alice-|/John: Hello John, how are you?
+      Alice-|/John: Hi Alice, I can hear you!
+      Alice-|/John: Test
+      `
+      );
+    });
+
+    it('should render Stick half arrow top ', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice-\\\\John: Hello John, how are you?
+      Alice-\\\\John: Hi Alice, I can hear you!
+      Alice-\\\\John: Test
+      `
+      );
+    });
+    it('should render Stick half arrow bottom ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice-//John: Hello John, how are you?
+      Alice-//John: Hi Alice, I can hear you!
+      Alice-//John: Test
+      `
+      );
+    });
+    it('should render Solid half arrow top reverse ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice/|-John: Hello Alice, how are you?
+      Alice/|-John: Hi Alice, I can hear you!
+      Alice/|-John: Test
+
+      `
+      );
+    });
+
+    it('should render Solid half arrow bottom reverse ', () => {
+      imgSnapshotTest(
+        `sequenceDiagram
+        Alice \\|- John: Hello Alice, how are you?
+        Alice \\|- John: Hi Alice, I can hear you!
+        Alice \\|- John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top reverse ', () => {
+      imgSnapshotTest(
+        `
+      sequenceDiagram
+      Alice //-John: Hello Alice, how are you?
+      Alice //-John: Hi Alice, I can hear you!
+      Alice //-John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom reverse ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice \\\\-John: Hello Alice, how are you?
+      Alice \\\\-John: Hi Alice, I can hear you!
+      Alice \\\\-John: Test`
+      );
+    });
+
+    it('should render Solid half arrow top dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice --|\\John: Hello John, how are you?
+      Alice --|\\John: Hi Alice, I can hear you!
+      Alice --|\\John: Test`
+      );
+    });
+
+    it('should render Solid half arrow bottom dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice --|/John: Hello John, how are you?
+      Alice --|/John: Hi Alice, I can hear you!
+      Alice --|/John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice--\\\\John: Hello John, how are you?
+      Alice--\\\\John: Hi Alice, I can hear you!
+      Alice--\\\\John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice--//John: Hello John, how are you?
+      Alice--//John: Hi Alice, I can hear you!
+      Alice--//John: Test`
+      );
+    });
+
+    it('should render Solid half arrow top reverse dotted', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice/|--John: Hello Alice, how are you?
+      Alice/|--John: Hi Alice, I can hear you!
+      Alice/|--John: Test`
+      );
+    });
+
+    it('should render Solid half arrow bottom reverse dotted', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice\\|--John: Hello Alice, how are you?
+      Alice\\|--John: Hi Alice, I can hear you!
+      Alice\\|--John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top reverse dotted ', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice//--John: Hello Alice, how are you?
+      Alice//--John: Hi Alice, I can hear you!
+      Alice//--John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom reverse dotted ', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice\\\\--John: Hello Alice, how are you?
+      Alice\\\\--John: Hi Alice, I can hear you!
+      Alice\\\\--John: Test`
+      );
+    });
+  });
 });

demos/er.html

@@ -169,164 +169,6 @@
     </pre>
     <hr />
 
-    <!-- Aggregation Examples -->
-    <h2>Aggregation Examples</h2>
-
-    <h3>Basic Aggregation (Solid Line)</h3>
-    <pre class="mermaid">
-    erDiagram
-      DEPARTMENT <> EMPLOYEE : contains
-      DEPARTMENT {
-          int id PK
-          string name
-          string location
-      }
-      EMPLOYEE {
-          int id PK
-          string name
-          int department_id FK
-      }
-    </pre>
-    <hr />
-
-    <h3>Dashed Aggregation</h3>
-    <pre class="mermaid">
-    erDiagram
-      PROJECT <>.. TASK : manages
-      PROJECT {
-          int id PK
-          string name
-          string description
-      }
-      TASK {
-          int id PK
-          string title
-          int project_id FK
-      }
-    </pre>
-    <hr />
-
-    <h3>Aggregation with Different Cardinalities</h3>
-    <pre class="mermaid">
-    erDiagram
-      COMPANY <> DEPARTMENT : owns
-      DEPARTMENT <> EMPLOYEE : contains
-      EMPLOYEE <> PROJECT : works_on
-      PROJECT <> TASK : consists_of
-      
-      COMPANY {
-          int id PK
-          string name
-      }
-      DEPARTMENT {
-          int id PK
-          string name
-          int company_id FK
-      }
-      EMPLOYEE {
-          int id PK
-          string name
-          int department_id FK
-      }
-      PROJECT {
-          int id PK
-          string name
-          int employee_id FK
-      }
-      TASK {
-          int id PK
-          string title
-          int project_id FK
-      }
-    </pre>
-    <hr />
-
-    <h3>Two-way Aggregation</h3>
-    <pre class="mermaid">
-    erDiagram
-      TEAM <> MEMBER : consists_of
-      TEAM {
-          int id PK
-          string name
-      }
-      MEMBER {
-          int id PK
-          string name
-          int team_id FK
-      }
-    </pre>
-    <hr />
-
-    <h3>Complex Aggregation with Labels</h3>
-    <pre class="mermaid">
-    erDiagram
-      UNIVERSITY <> COLLEGE : "has multiple"
-      COLLEGE <> DEPARTMENT : "contains"
-      DEPARTMENT <> FACULTY : "employs"
-      FACULTY <> STUDENT : "teaches"
-      
-      UNIVERSITY {
-          int id PK
-          string name
-      }
-      COLLEGE {
-          int id PK
-          string name
-          int university_id FK
-      }
-      DEPARTMENT {
-          int id PK
-          string name
-          int college_id FK
-      }
-      FACULTY {
-          int id PK
-          string name
-          int department_id FK
-      }
-      STUDENT {
-          int id PK
-          string name
-          int faculty_id FK
-      }
-    </pre>
-    <hr />
-
-    <h3>Mixed Relationship Types</h3>
-    <pre class="mermaid">
-    erDiagram
-      CUSTOMER ||--o{ ORDER : places
-      ORDER ||--|{ ORDER_ITEM : contains
-      PRODUCT <> ORDER_ITEM : "aggregated in"
-      WAREHOUSE <>.. PRODUCT : "stores"
-      
-      CUSTOMER {
-          int id PK
-          string name
-      }
-      ORDER {
-          int id PK
-          int customer_id FK
-          date order_date
-      }
-      ORDER_ITEM {
-          int id PK
-          int order_id FK
-          int product_id FK
-          int quantity
-      }
-      PRODUCT {
-          int id PK
-          string name
-          int warehouse_id FK
-      }
-      WAREHOUSE {
-          int id PK
-          string name
-      }
-    </pre>
-    <hr />
-
     <script type="module">
       import mermaid from './mermaid.esm.mjs';
       mermaid.initialize({

docs/config/faq.md

@@ -6,7 +6,7 @@
 
 # Frequently Asked Questions
 
-1. [How to add title to flowchart?](https://github.com/mermaid-js/mermaid/issues/556#issuecomment-363182217)
+1. [How to add title to flowchart?](https://github.com/mermaid-js/mermaid/issues/1433#issuecomment-1991554712)
 2. [How to specify custom CSS file?](https://github.com/mermaidjs/mermaid.cli/pull/24#issuecomment-373402785)
 3. [How to fix tooltip misplacement issue?](https://github.com/mermaid-js/mermaid/issues/542#issuecomment-3343564621)
 4. [How to specify gantt diagram xAxis format?](https://github.com/mermaid-js/mermaid/issues/269#issuecomment-373229136)

docs/syntax/entityRelationshipDiagram.md

@@ -209,42 +209,6 @@ erDiagram
     PERSON many(0) optionally to 0+ NAMED-DRIVER : is
 ```
 
-### Aggregation
-
-Aggregation represents a "has-a" relationship where the part can exist independently of the whole. This is different from composition, where the part cannot exist without the whole. Aggregation relationships are rendered with hollow diamond markers at the endpoints.
-
-| Value |      Alias for       | Description                    |
-| :---: | :------------------: | ------------------------------ |
-|  <>   |    _aggregation_     | Basic aggregation (solid line) |
-| <>..  | _aggregation-dashed_ | Dashed aggregation line        |
-
-**Examples:**
-
-```mermaid-example
-erDiagram
-    DEPARTMENT <> EMPLOYEE : contains
-    PROJECT <>.. TASK : manages
-    TEAM <> MEMBER : consists_of
-```
-
-```mermaid
-erDiagram
-    DEPARTMENT <> EMPLOYEE : contains
-    PROJECT <>.. TASK : manages
-    TEAM <> MEMBER : consists_of
-```
-
-In these examples:
-
-- `DEPARTMENT <> EMPLOYEE` shows that a department contains employees (aggregation)
-- `PROJECT <>.. TASK` shows that a project manages tasks (dashed aggregation)
-- `TEAM <> MEMBER` shows that a team consists of members (aggregation)
-
-**Aggregation vs Association**
-
-- **Aggregation** (`<>`): "Has-a" relationship where parts can exist independently
-- **Association** (`||--`, `}o--`): General relationship between entities
-
 ### Attributes
 
 Attributes can be defined for entities by specifying the entity name followed by a block containing multiple `type name` pairs, where a block is delimited by an opening `{` and a closing `}`. The attributes are rendered inside the entity boxes. For example:

docs/syntax/sequenceDiagram.md

@@ -329,7 +329,11 @@ Messages can be of two displayed either solid or with a dotted line.
 [Actor][Arrow][Actor]:Message text
 ```
 
-There are ten types of arrows currently supported:
+Lines can be solid or dotted, and can end with various types of arrowheads, crosses, or open arrows.
+
+#### Supported Arrow Types
+
+**Standard Arrow Types**
 
 | Type     | Description                                          |
 | -------- | ---------------------------------------------------- |
@@ -344,6 +348,58 @@ There are ten types of arrows currently supported:
 | `-)`     | Solid line with an open arrow at the end (async)     |
 | `--)`    | Dotted line with a open arrow at the end (async)     |
 
+**Half-Arrows (v\<MERMAID_RELEASE_VERSION>+)**
+
+The following half-arrow types are supported for more expressive sequence diagrams. Both solid and dotted variants are available by increasing the number of dashes (`-` → `--`).
+
+---
+
+| Type    | Description                                          |
+| ------- | ---------------------------------------------------- |
+| `-\|\`  | Solid line with top half arrowhead                   |
+| `--\|\` | Dotted line with top half arrowhead                  |
+| `-\|/`  | Solid line with bottom half arrowhead                |
+| `--\|/` | Dotted line with bottom half arrowhead               |
+| `/\|-`  | Solid line with reverse top half arrowhead           |
+| `/\|--` | Dotted line with reverse top half arrowhead          |
+| `\\-`   | Solid line with reverse bottom half arrowhead        |
+| `\\--`  | Dotted line with reverse bottom half arrowhead       |
+| `-\\`   | Solid line with top stick half arrowhead             |
+| `--\\`  | Dotted line with top stick half arrowhead            |
+| `-//`   | Solid line with bottom stick half arrowhead          |
+| `--//`  | Dotted line with bottom stick half arrowhead         |
+| `//-`   | Solid line with reverse top stick half arrowhead     |
+| `//--`  | Dotted line with reverse top stick half arrowhead    |
+| `\\-`   | Solid line with reverse bottom stick half arrowhead  |
+| `\\--`  | Dotted line with reverse bottom stick half arrowhead |
+
+## Central Connections (v\<MERMAID_RELEASE_VERSION>+)
+
+Mermaid sequence diagrams support **central lifeline connections** using a `()`.
+This is useful to represent messages or signals that connect to a central point, rather than from one actor directly to another.
+
+To indicate a central connection, append `()` to the arrow syntax.
+
+#### Basic Syntax
+
+```mermaid-example
+sequenceDiagram
+    participant Alice
+    participant John
+    Alice->>()John: Hello John
+    Alice()->>John: How are you?
+    John()->>()Alice: Great!
+```
+
+```mermaid
+sequenceDiagram
+    participant Alice
+    participant John
+    Alice->>()John: Hello John
+    Alice()->>John: How are you?
+    John()->>()Alice: Great!
+```
+
 ## Activations
 
 It is possible to activate and deactivate an actor. (de)activation can be dedicated declarations:

packages/mermaid/src/diagrams/class/classDiagram.spec.ts

@@ -1070,6 +1070,14 @@ describe('given a class diagram with members and methods ', function () {
 
       parser.parse(str);
     });
+    it('should handle an empty class body with {}', function () {
+      const str = 'classDiagram\nclass EmptyClass {}';
+      parser.parse(str);
+      const actual = parser.yy.getClass('EmptyClass');
+      expect(actual.label).toBe('EmptyClass');
+      expect(actual.members.length).toBe(0);
+      expect(actual.methods.length).toBe(0);
+    });
   });
 });
 

packages/mermaid/src/diagrams/class/parser/classDiagram.jison

@@ -293,6 +293,7 @@ classStatement
     : classIdentifier
     | classIdentifier STYLE_SEPARATOR alphaNumToken      {yy.setCssClass($1, $3);}
     | classIdentifier STRUCT_START members STRUCT_STOP   {yy.addMembers($1,$3);}
+    | classIdentifier STRUCT_START STRUCT_STOP           {}
     | classIdentifier STYLE_SEPARATOR alphaNumToken STRUCT_START members STRUCT_STOP {yy.setCssClass($1, $3);yy.addMembers($1,$5);}
     ;
 
@@ -301,8 +302,15 @@ classIdentifier
     | CLASS className classLabel                         {$$=$2; yy.addClass($2);yy.setClassLabel($2, $3);}
     ;
 
+
+emptyBody
+    :
+    | SPACE emptyBody
+    | NEWLINE emptyBody
+    ;
+
 annotationStatement
-    :ANNOTATION_START alphaNumToken ANNOTATION_END className  { yy.addAnnotation($4,$2); }
+    : ANNOTATION_START alphaNumToken ANNOTATION_END className  { yy.addAnnotation($4,$2); }
     ;
 
 members

packages/mermaid/src/diagrams/er/erDb.ts

@@ -2,7 +2,6 @@ import { log } from '../../logger.js';
 import { getConfig } from '../../diagram-api/diagramAPI.js';
 import type { Edge, Node } from '../../rendering-util/types.js';
 import type { EntityNode, Attribute, Relationship, EntityClass, RelSpec } from './erTypes.js';
-import { AggregationType } from './erTypes.js';
 import {
   setAccTitle,
   getAccTitle,
@@ -34,11 +33,6 @@ export class ErDB implements DiagramDB {
     IDENTIFYING: 'IDENTIFYING',
   };
 
-  private Aggregation = {
-    AGGREGATION: AggregationType.AGGREGATION,
-    AGGREGATION_DASHED: AggregationType.AGGREGATION_DASHED,
-  };
-
   constructor() {
     this.clear();
     this.addEntity = this.addEntity.bind(this);
@@ -137,31 +131,6 @@ export class ErDB implements DiagramDB {
     return this.relationships;
   }
 
-  /**
-   * Validate aggregation relationship
-   * @param rSpec - The relationship specification to validate
-   * @returns boolean indicating if the aggregation relationship is valid
-   */
-  public validateAggregationRelationship(rSpec: RelSpec): boolean {
-    const isAggregation =
-      rSpec.relType === this.Aggregation.AGGREGATION ||
-      rSpec.relType === this.Aggregation.AGGREGATION_DASHED;
-
-    if (!isAggregation) {
-      return false;
-    }
-
-    const validCardinalities = [
-      this.Cardinality.ZERO_OR_ONE,
-      this.Cardinality.ZERO_OR_MORE,
-      this.Cardinality.ONE_OR_MORE,
-      this.Cardinality.ONLY_ONE,
-      this.Cardinality.MD_PARENT,
-    ];
-
-    return validCardinalities.includes(rSpec.cardA) && validCardinalities.includes(rSpec.cardB);
-  }
-
   public getDirection() {
     return this.direction;
   }
@@ -279,17 +248,4 @@ export class ErDB implements DiagramDB {
   public setDiagramTitle = setDiagramTitle;
   public getDiagramTitle = getDiagramTitle;
   public getConfig = () => getConfig().er;
-
-  // Getter methods for aggregation constants
-  public get AggregationConstants() {
-    return this.Aggregation;
-  }
-
-  public get CardinalityConstants() {
-    return this.Cardinality;
-  }
-
-  public get IdentificationConstants() {
-    return this.Identification;
-  }
 }

packages/mermaid/src/diagrams/er/erMarkers.js

@@ -9,10 +9,6 @@ const ERMarkers = {
   ZERO_OR_MORE_END: 'ZERO_OR_MORE_END',
   MD_PARENT_END: 'MD_PARENT_END',
   MD_PARENT_START: 'MD_PARENT_START',
-  AGGREGATION_START: 'AGGREGATION_START',
-  AGGREGATION_END: 'AGGREGATION_END',
-  AGGREGATION_DASHED_START: 'AGGREGATION_DASHED_START',
-  AGGREGATION_DASHED_END: 'AGGREGATION_DASHED_END',
 };
 
 /**
@@ -184,66 +180,6 @@ const insertMarkers = function (elem, conf) {
     .attr('fill', 'none')
     .attr('d', 'M21,18 Q39,0 57,18 Q39,36 21,18');
 
-  // Aggregation markers (hollow diamond)
-  elem
-    .append('defs')
-    .append('marker')
-    .attr('id', ERMarkers.AGGREGATION_START)
-    .attr('refX', 0)
-    .attr('refY', 9)
-    .attr('markerWidth', 20)
-    .attr('markerHeight', 18)
-    .attr('orient', 'auto')
-    .append('path')
-    .attr('stroke', conf.stroke)
-    .attr('fill', 'white')
-    .attr('d', 'M18,9 L9,0 L0,9 L9,18 Z');
-
-  elem
-    .append('defs')
-    .append('marker')
-    .attr('id', ERMarkers.AGGREGATION_END)
-    .attr('refX', 20)
-    .attr('refY', 9)
-    .attr('markerWidth', 20)
-    .attr('markerHeight', 18)
-    .attr('orient', 'auto')
-    .append('path')
-    .attr('stroke', conf.stroke)
-    .attr('fill', 'white')
-    .attr('d', 'M2,9 L11,0 L20,9 L11,18 Z');
-
-  // Dashed aggregation markers
-  elem
-    .append('defs')
-    .append('marker')
-    .attr('id', ERMarkers.AGGREGATION_DASHED_START)
-    .attr('refX', 0)
-    .attr('refY', 9)
-    .attr('markerWidth', 20)
-    .attr('markerHeight', 18)
-    .attr('orient', 'auto')
-    .append('path')
-    .attr('stroke', conf.stroke)
-    .attr('fill', 'white')
-    .attr('stroke-dasharray', '3,3')
-    .attr('d', 'M18,9 L9,0 L0,9 L9,18 Z');
-
-  elem
-    .append('defs')
-    .append('marker')
-    .attr('id', ERMarkers.AGGREGATION_DASHED_END)
-    .attr('refX', 20)
-    .attr('refY', 9)
-    .attr('markerWidth', 20)
-    .attr('markerHeight', 18)
-    .attr('orient', 'auto')
-    .append('path')
-    .attr('stroke', conf.stroke)
-    .attr('fill', 'white')
-    .attr('stroke-dasharray', '3,3')
-    .attr('d', 'M2,9 L11,0 L20,9 L11,18 Z');
-
   return;
 };
 

packages/mermaid/src/diagrams/er/erRenderer.js

@@ -448,11 +448,6 @@ const drawRelationshipFromLayout = function (svg, rel, g, insert, diagObj) {
     svgPath.attr('stroke-dasharray', '8,8');
   }
 
-  // Handle aggregation relationship styling
-  if (rel.relSpec.relType === diagObj.db.Aggregation.AGGREGATION_DASHED) {
-    svgPath.attr('stroke-dasharray', '8,8');
-  }
-
   // TODO: Understand this better
   let url = '';
   if (conf.arrowMarkerAbsolute) {
@@ -508,15 +503,6 @@ const drawRelationshipFromLayout = function (svg, rel, g, insert, diagObj) {
       break;
   }
 
-  // Handle aggregation markers
-  if (
-    rel.relSpec.relType === diagObj.db.Aggregation.AGGREGATION ||
-    rel.relSpec.relType === diagObj.db.Aggregation.AGGREGATION_DASHED
-  ) {
-    // Add aggregation marker at the start (entity B side)
-    svgPath.attr('marker-start', 'url(' + url + '#' + erMarkers.ERMarkers.AGGREGATION_START + ')');
-  }
-
   // Now label the relationship
 
   // Find the half-way point

packages/mermaid/src/diagrams/er/erTypes.ts

@@ -35,15 +35,3 @@ export interface EntityClass {
   styles: string[];
   textStyles: string[];
 }
-
-// Aggregation relationship types
-export const AggregationType = {
-  AGGREGATION: 'AGGREGATION',
-  AGGREGATION_DASHED: 'AGGREGATION_DASHED',
-} as const;
-
-// Line types for aggregation
-export const AggregationLineType = {
-  SOLID: 'SOLID',
-  DASHED: 'DASHED',
-} as const;

packages/mermaid/src/diagrams/er/parser/erDiagram.jison

@@ -72,8 +72,6 @@ o\|                             return 'ZERO_OR_ONE';
 o\{                             return 'ZERO_OR_MORE';
 \|\{                            return 'ONE_OR_MORE';
 \s*u                            return 'MD_PARENT';
-"<>.."                          return 'AGGREGATION_DASHED';
-"<>"                            return 'AGGREGATION';
 \.\.                            return 'NON_IDENTIFYING';
 \-\-                            return 'IDENTIFYING';
 "to"                            return 'IDENTIFYING';
@@ -169,47 +167,6 @@ statement
     | entityName SQS entityName SQE STYLE_SEPARATOR idList BLOCK_START BLOCK_STOP { yy.addEntity($1, $3); yy.setClass([$1], $6); }
     | entityName SQS entityName SQE { yy.addEntity($1, $3); }
     | entityName SQS entityName SQE STYLE_SEPARATOR idList { yy.addEntity($1, $3); yy.setClass([$1], $6); }
-    | entityName aggregationRelSpec entityName COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($3);
-          yy.addRelationship($1, $5, $3, $2);
-      }
-    | entityName STYLE_SEPARATOR idList aggregationRelSpec entityName STYLE_SEPARATOR idList COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($5);
-          yy.addRelationship($1, $9, $5, $4);
-          yy.setClass([$1], $3);
-          yy.setClass([$5], $7);
-      }
-    | entityName STYLE_SEPARATOR idList aggregationRelSpec entityName COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($5);
-          yy.addRelationship($1, $7, $5, $4);
-          yy.setClass([$1], $3);
-      }
-    | entityName aggregationRelSpec entityName STYLE_SEPARATOR idList COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($3);
-          yy.addRelationship($1, $7, $3, $2);
-          yy.setClass([$3], $5);
-      }
-    | entityName 'AGGREGATION' entityName COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($3);
-          yy.addRelationship($1, $5, $3, { cardA: 'ZERO_OR_MORE', relType: 'AGGREGATION', cardB: 'ZERO_OR_MORE' });
-      }
-    | entityName 'AGGREGATION_DASHED' entityName COLON role
-      {
-          yy.addEntity($1);
-          yy.addEntity($3);
-          yy.addRelationship($1, $5, $3, { cardA: 'ZERO_OR_MORE', relType: 'AGGREGATION_DASHED', cardB: 'ZERO_OR_MORE' });
-      }
-
     | title title_value  { $$=$2.trim();yy.setAccTitle($$); }
     | acc_title acc_title_value  { $$=$2.trim();yy.setAccTitle($$); }
     | acc_descr acc_descr_value  { $$=$2.trim();yy.setAccDescription($$); }
@@ -315,17 +272,6 @@ relSpec
       }
     ;
 
-aggregationRelSpec
-    : 'AGGREGATION' cardinality cardinality
-      {
-        $$ = { cardA: $2, relType: $1, cardB: $3 };
-      }
-    | 'AGGREGATION_DASHED' cardinality cardinality
-      {
-        $$ = { cardA: $2, relType: $1, cardB: $3 };
-      }
-    ;
-
 cardinality
     : 'ZERO_OR_ONE'                  { $$ = yy.Cardinality.ZERO_OR_ONE; }
     | 'ZERO_OR_MORE'                 { $$ = yy.Cardinality.ZERO_OR_MORE; }
@@ -337,8 +283,6 @@ cardinality
 relType
     : 'NON_IDENTIFYING'              { $$ = yy.Identification.NON_IDENTIFYING;  }
     | 'IDENTIFYING'                  { $$ = yy.Identification.IDENTIFYING; }
-    | 'AGGREGATION'                  { $$ = yy.Aggregation.AGGREGATION; }
-    | 'AGGREGATION_DASHED'           { $$ = yy.Aggregation.AGGREGATION_DASHED; }
     ;
 
 role

packages/mermaid/src/diagrams/er/parser/erDiagram.spec.js

@@ -1001,75 +1001,4 @@ describe('when parsing ER diagram it...', function () {
       }
     );
   });
-
-  describe('aggregation relationships', function () {
-    it('should parse basic aggregation syntax', function () {
-      erDiagram.parser.parse('erDiagram\nDEPARTMENT <> EMPLOYEE : contains');
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(2);
-      expect(rels.length).toBe(1);
-      expect(rels[0].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION);
-      expect(rels[0].relSpec.cardA).toBe(erDb.Cardinality.ZERO_OR_MORE);
-      expect(rels[0].relSpec.cardB).toBe(erDb.Cardinality.ZERO_OR_MORE);
-      expect(rels[0].roleA).toBe('contains');
-    });
-
-    it('should parse dashed aggregation syntax', function () {
-      erDiagram.parser.parse('erDiagram\nPROJECT <>.. TASK : manages');
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(2);
-      expect(rels.length).toBe(1);
-      expect(rels[0].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION_DASHED);
-      expect(rels[0].relSpec.cardA).toBe(erDb.Cardinality.ZERO_OR_MORE);
-      expect(rels[0].relSpec.cardB).toBe(erDb.Cardinality.ZERO_OR_MORE);
-      expect(rels[0].roleA).toBe('manages');
-    });
-
-    it('should parse aggregation with quoted labels', function () {
-      erDiagram.parser.parse('erDiagram\nUNIVERSITY <> COLLEGE : "has multiple"');
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(2);
-      expect(rels.length).toBe(1);
-      expect(rels[0].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION);
-      expect(rels[0].roleA).toBe('has multiple');
-    });
-
-    it('should parse multiple aggregation relationships', function () {
-      erDiagram.parser.parse(
-        'erDiagram\nDEPARTMENT <> EMPLOYEE : contains\nPROJECT <>.. TASK : manages'
-      );
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(4);
-      expect(rels.length).toBe(2);
-      expect(rels[0].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION);
-      expect(rels[1].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION_DASHED);
-    });
-
-    it('should parse aggregation with entity aliases', function () {
-      erDiagram.parser.parse('erDiagram\nd[DEPARTMENT]\ne[EMPLOYEE]\nd <> e : contains');
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(2);
-      expect(rels.length).toBe(1);
-      expect(rels[0].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION);
-      expect(erDb.getEntity('d').alias).toBe('DEPARTMENT');
-      expect(erDb.getEntity('e').alias).toBe('EMPLOYEE');
-    });
-
-    it('should validate aggregation relationships', function () {
-      erDiagram.parser.parse('erDiagram\nDEPARTMENT <> EMPLOYEE : contains');
-      const rels = erDb.getRelationships();
-      expect(erDb.validateAggregationRelationship(rels[0].relSpec)).toBe(true);
-    });
-
-    it('should handle mixed relationship types', function () {
-      erDiagram.parser.parse(
-        'erDiagram\nCUSTOMER ||--o{ ORDER : places\nPRODUCT <> ORDER_ITEM : "aggregated in"'
-      );
-      const rels = erDb.getRelationships();
-      expect(erDb.getEntities().size).toBe(4);
-      expect(rels.length).toBe(2);
-      expect(rels[0].relSpec.relType).toBe(erDb.Identification.IDENTIFYING);
-      expect(rels[1].relSpec.relType).toBe(erDb.Aggregation.AGGREGATION);
-    });
-  });
 });

packages/mermaid/src/diagrams/er/styles.ts

@@ -68,32 +68,6 @@ const getStyles = (options: FlowChartStyleOptions) =>
     stroke: ${options.lineColor} !important;
     stroke-width: 1;
   }
-
-  .aggregation {
-    stroke: ${options.lineColor};
-    stroke-width: 1;
-    fill: white;
-  }
-
-  .aggregation-dashed {
-    stroke: ${options.lineColor};
-    stroke-width: 1;
-    stroke-dasharray: 8,8;
-    fill: white;
-  }
-
-  .aggregation-marker {
-    fill: white !important;
-    stroke: ${options.lineColor} !important;
-    stroke-width: 1;
-  }
-
-  .aggregation-marker-dashed {
-    fill: white !important;
-    stroke: ${options.lineColor} !important;
-    stroke-width: 1;
-    stroke-dasharray: 3,3;
-  }
 `;
 
 export default getStyles;

packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison

@@ -78,7 +78,7 @@ accDescr\s*"{"\s*                                { this.begin("acc_descr_multili
 "off"															return 'off';
 ","                                                             return ',';
 ";"                                                             return 'NEWLINE';
-[^+<\->\->:\n,;]+((?!(\-x|\-\-x|\-\)|\-\-\)))[\-]*[^\+<\->\->:\n,;]+)*             { yytext = yytext.trim(); return 'ACTOR'; }
+[^\/\\\+\()\+<\->\->:\n,;]+((?!(\-x|\-\-x|\-\)|\-\-\)|\-\|\\|\-\\|\-\/|\-\/\/|\-\|\/|\/\|\-|\\\|\-|\/\/\-|\\\\\-|\/\|\-|\-\-\|\\|\-\-|\(\)))[\-]*[^\+<\->\->:\n,;]+)*             { yytext = yytext.trim(); return 'ACTOR'; } //final_4.11
 "->>"                                                           return 'SOLID_ARROW';
 "<<->>"                                                           return 'BIDIRECTIONAL_SOLID_ARROW';
 "-->>"                                                          return 'DOTTED_ARROW';
@@ -89,10 +89,36 @@ accDescr\s*"{"\s*                                { this.begin("acc_descr_multili
 \-\-[x]                                                         return 'DOTTED_CROSS';
 \-[\)]                                                          return 'SOLID_POINT';
 \-\-[\)]                                                        return 'DOTTED_POINT';
+
+//normal-dotted
+\-\-\|\\                                                        return 'SOLID_ARROW_TOP_DOTTED';
+\-\-\|\/                                                        return 'SOLID_ARROW_BOTTOM_DOTTED';
+\-\-\\\\                                                        return 'STICK_ARROW_TOP_DOTTED';
+\-\-\/\/                                                        return 'STICK_ARROW_BOTTOM_DOTTED';
+
+//reverse-dotted
+\/\|\-\-                                                          return 'SOLID_ARROW_TOP_REVERSE_DOTTED';
+\\\|\-\-                                                          return 'SOLID_ARROW_BOTTOM_REVERSE_DOTTED';
+\/\/\-\-                                                          return 'STICK_ARROW_TOP_REVERSE_DOTTED';
+\\\\\-\-                                                          return 'STICK_ARROW_BOTTOM_REVERSE_DOTTED';
+
+//normal
+\-\|\\                                                          return 'SOLID_ARROW_TOP';
+\-\|\/                                                          return 'SOLID_ARROW_BOTTOM';
+\-\\\\                                                          return 'STICK_ARROW_TOP';
+\-\/\/                                                          return 'STICK_ARROW_BOTTOM';
+
+//reverse
+\/\|\-                                                          return 'SOLID_ARROW_TOP_REVERSE';
+\\\|\-                                                          return 'SOLID_ARROW_BOTTOM_REVERSE';
+\/\/\-                                                          return 'STICK_ARROW_TOP_REVERSE';
+\\\\\-                                                          return 'STICK_ARROW_BOTTOM_REVERSE';
+
 ":"(?:(?:no)?wrap:)?[^#\n;]*                                    return 'TXT';
 ":"                             								return 'TXT';
 "+"                                                             return '+';
 "-"                                                             return '-';
+"()"                                                            return '()';
 <<EOF>>                                                         return 'NEWLINE';
 .                                                               return 'INVALID';
 
@@ -304,6 +330,20 @@ signal
 	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$2, msg:$5},
 	             {type: 'activeEnd', signalType: yy.LINETYPE.ACTIVE_END, actor: $1.actor}
 	             ]}
+    | actor signaltype '()' actor text2
+	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$2, msg:$5, activate: true, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION},
+	              {type: 'centralConnection', signalType: yy.LINETYPE.CENTRAL_CONNECTION, actor: $4.actor, }
+	             ]}
+    
+	| actor '()' signaltype actor text2
+	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$3, msg:$5, activate: false, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE},
+	              {type: 'centralConnectionReverse', signalType: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE, actor: $1.actor}
+	             ]}
+	| actor '()' signaltype '()' actor text2
+	{ $$ = [$1,$5,{type: 'addMessage', from:$1.actor, to:$5.actor, signalType:$3, msg:$6, activate: true, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION_DUAL},
+	 			 {type: 'centralConnection', signalType: yy.LINETYPE.CENTRAL_CONNECTION, actor: $5.actor, },
+				 {type: 'centralConnectionReverse', signalType: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE, actor: $1.actor}
+	             ]}
 	| actor signaltype actor text2
 	{ $$ = [$1,$3,{type: 'addMessage', from:$1.actor, to:$3.actor, signalType:$2, msg:$4}]}
 	;
@@ -337,7 +377,28 @@ signaltype
 	: SOLID_OPEN_ARROW  { $$ = yy.LINETYPE.SOLID_OPEN; }
 	| DOTTED_OPEN_ARROW { $$ = yy.LINETYPE.DOTTED_OPEN; }
 	| SOLID_ARROW       { $$ = yy.LINETYPE.SOLID; }
-	| BIDIRECTIONAL_SOLID_ARROW       { $$ = yy.LINETYPE.BIDIRECTIONAL_SOLID; }
+	
+	| SOLID_ARROW_TOP    { $$ = yy.LINETYPE.SOLID_TOP; }
+	| SOLID_ARROW_BOTTOM { $$ = yy.LINETYPE.SOLID_BOTTOM; }
+	| STICK_ARROW_TOP    { $$ = yy.LINETYPE.STICK_TOP; }
+	| STICK_ARROW_BOTTOM { $$ = yy.LINETYPE.STICK_BOTTOM; }
+
+	| SOLID_ARROW_TOP_DOTTED    { $$ = yy.LINETYPE.SOLID_TOP_DOTTED; }	
+	| SOLID_ARROW_BOTTOM_DOTTED { $$ = yy.LINETYPE.SOLID_BOTTOM_DOTTED; }
+	| STICK_ARROW_TOP_DOTTED    { $$ = yy.LINETYPE.STICK_TOP_DOTTED; }
+	| STICK_ARROW_BOTTOM_DOTTED { $$ = yy.LINETYPE.STICK_BOTTOM_DOTTED; }
+
+	| SOLID_ARROW_TOP_REVERSE    { $$ = yy.LINETYPE.SOLID_ARROW_TOP_REVERSE; }
+	| SOLID_ARROW_BOTTOM_REVERSE { $$ = yy.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE; }
+	| STICK_ARROW_TOP_REVERSE    { $$ = yy.LINETYPE.STICK_ARROW_TOP_REVERSE; }
+	| STICK_ARROW_BOTTOM_REVERSE { $$ = yy.LINETYPE.STICK_ARROW_BOTTOM_REVERSE; }
+
+	| SOLID_ARROW_TOP_REVERSE_DOTTED    { $$ = yy.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED; }
+	| SOLID_ARROW_BOTTOM_REVERSE_DOTTED { $$ = yy.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED; }
+	| STICK_ARROW_TOP_REVERSE_DOTTED    { $$ = yy.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED; }
+	| STICK_ARROW_BOTTOM_REVERSE_DOTTED { $$ = yy.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED; }
+
+  | BIDIRECTIONAL_SOLID_ARROW       { $$ = yy.LINETYPE.BIDIRECTIONAL_SOLID; }
 	| DOTTED_ARROW      { $$ = yy.LINETYPE.DOTTED; }
 	| BIDIRECTIONAL_DOTTED_ARROW      { $$ = yy.LINETYPE.BIDIRECTIONAL_DOTTED; }
 	| SOLID_CROSS       { $$ = yy.LINETYPE.SOLID_CROSS; }

packages/mermaid/src/diagrams/sequence/sequenceDb.ts

@@ -64,6 +64,30 @@ const LINETYPE = {
   PAR_OVER_START: 32,
   BIDIRECTIONAL_SOLID: 33,
   BIDIRECTIONAL_DOTTED: 34,
+
+  SOLID_TOP: 41,
+  SOLID_BOTTOM: 42,
+  STICK_TOP: 43,
+  STICK_BOTTOM: 44,
+
+  SOLID_ARROW_TOP_REVERSE: 45,
+  SOLID_ARROW_BOTTOM_REVERSE: 46,
+  STICK_ARROW_TOP_REVERSE: 47,
+  STICK_ARROW_BOTTOM_REVERSE: 48,
+
+  SOLID_TOP_DOTTED: 51,
+  SOLID_BOTTOM_DOTTED: 52,
+  STICK_TOP_DOTTED: 53,
+  STICK_BOTTOM_DOTTED: 54,
+
+  SOLID_ARROW_TOP_REVERSE_DOTTED: 55,
+  SOLID_ARROW_BOTTOM_REVERSE_DOTTED: 56,
+  STICK_ARROW_TOP_REVERSE_DOTTED: 57,
+  STICK_ARROW_BOTTOM_REVERSE_DOTTED: 58,
+
+  CENTRAL_CONNECTION: 59,
+  CENTRAL_CONNECTION_REVERSE: 60,
+  CENTRAL_CONNECTION_DUAL: 61,
 } as const;
 
 const ARROWTYPE = {
@@ -244,7 +268,8 @@ export class SequenceDB implements DiagramDB {
     idTo?: Message['to'],
     message?: { text: string; wrap: boolean },
     messageType?: number,
-    activate = false
+    activate = false,
+    centralConnection?: number
   ) {
     if (messageType === this.LINETYPE.ACTIVE_END) {
       const cnt = this.activationCount(idFrom ?? '');
@@ -271,6 +296,7 @@ export class SequenceDB implements DiagramDB {
       wrap: message?.wrap ?? this.autoWrap(),
       type: messageType,
       activate,
+      centralConnection: centralConnection ?? 0,
     });
     return true;
   }
@@ -563,6 +589,12 @@ export class SequenceDB implements DiagramDB {
         case 'activeStart':
           this.addSignal(param.actor, undefined, undefined, param.signalType);
           break;
+        case 'centralConnection':
+          this.addSignal(param.actor, undefined, undefined, param.signalType);
+          break;
+        case 'centralConnectionReverse':
+          this.addSignal(param.actor, undefined, undefined, param.signalType);
+          break;
         case 'activeEnd':
           this.addSignal(param.actor, undefined, undefined, param.signalType);
           break;
@@ -606,7 +638,14 @@ export class SequenceDB implements DiagramDB {
               this.state.records.lastDestroyed = undefined;
             }
           }
-          this.addSignal(param.from, param.to, param.msg, param.signalType, param.activate);
+          this.addSignal(
+            param.from,
+            param.to,
+            param.msg,
+            param.signalType,
+            param.activate,
+            param.centralConnection
+          );
           break;
         case 'boxStart':
           this.addBox(param.boxData);

packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js

@@ -104,6 +104,7 @@ describe('more than one sequence diagram', () => {
       [
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "Alice",
           "id": "0",
           "message": "Hello Bob, how are you?",
@@ -113,6 +114,7 @@ describe('more than one sequence diagram', () => {
         },
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "Bob",
           "id": "1",
           "message": "I am good thanks!",
@@ -131,6 +133,7 @@ describe('more than one sequence diagram', () => {
       [
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "Alice",
           "id": "0",
           "message": "Hello Bob, how are you?",
@@ -140,6 +143,7 @@ describe('more than one sequence diagram', () => {
         },
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "Bob",
           "id": "1",
           "message": "I am good thanks!",
@@ -160,6 +164,7 @@ describe('more than one sequence diagram', () => {
       [
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "Alice",
           "id": "0",
           "message": "Hello John, how are you?",
@@ -169,6 +174,7 @@ describe('more than one sequence diagram', () => {
         },
         {
           "activate": false,
+          "centralConnection": 0,
           "from": "John",
           "id": "1",
           "message": "I am good thanks!",
@@ -181,6 +187,254 @@ describe('more than one sequence diagram', () => {
   });
 });
 
+describe('Central Connection Parsing', () => {
+  describe('when parsing central connection syntax', () => {
+    it('should parse actor ()->>() actor syntax as CENTRAL_CONNECTION_DUAL', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()->>() Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(3); // addMessage + centralConnection + centralConnectionReverse
+
+      // Find the actual message (type: 'addMessage')
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL
+        activate: true,
+        type: 0, // SOLID (based on test output)
+      });
+    });
+
+    it('should parse actor ()-->>() actor syntax as CENTRAL_CONNECTION_DUAL', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()-->>() Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(3); // addMessage + centralConnection + centralConnectionReverse
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL
+        activate: true,
+        type: 1, // DOTTED (based on test output)
+      });
+    });
+
+    it('should parse actor ->>() actor syntax as CENTRAL_CONNECTION', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ->>() Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(2); // addMessage + centralConnection (no activation for this pattern)
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 59, // CENTRAL_CONNECTION
+        activate: true,
+        type: 0, // SOLID (based on actual parsing)
+      });
+    });
+
+    it('should parse actor ()-->> actor syntax as CENTRAL_CONNECTION_REVERSE', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()-->> Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(2); // addMessage + centralConnectionReverse
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 60, // CENTRAL_CONNECTION_REVERSE
+        activate: false,
+        type: 1, // DOTTED (based on test output)
+      });
+    });
+
+    it('should parse actor ()->> actor syntax as CENTRAL_CONNECTION_REVERSE', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()->> Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(2); // addMessage + centralConnectionReverse
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 60, // CENTRAL_CONNECTION_REVERSE
+        activate: false,
+        type: 0, // SOLID (based on test output)
+      });
+    });
+
+    it('should parse actor ()<<-->>() actor syntax as CENTRAL_CONNECTION_DUAL', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()<<-->>() Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(3); // addMessage + centralConnection + centralConnectionReverse
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL
+        activate: true,
+        type: 34, // BIDIRECTIONAL_DOTTED
+      });
+    });
+
+    it('should parse actor ()<<->>() actor syntax as CENTRAL_CONNECTION_DUAL', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()<<->>() Bob: Hello Bob, how are you?
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(3); // addMessage + centralConnection + centralConnectionReverse
+
+      const actualMessage = messages.find((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessage).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        message: 'Hello Bob, how are you?',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL
+        activate: true,
+        type: 33, // BIDIRECTIONAL_SOLID
+      });
+    });
+
+    it('should handle multiple central connection types in one diagram', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Message 1
+        Bob ()-->> Charlie: Message 2
+        Charlie ()<<-->>() Alice: Message 3
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(8); // 3 addMessages + 5 central connection markers
+
+      // Filter to get only the actual messages
+      const actualMessages = messages.filter((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessages).toHaveLength(3);
+
+      expect(actualMessages[0]).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL (()->>())
+      });
+
+      expect(actualMessages[1]).toMatchObject({
+        from: 'Bob',
+        to: 'Charlie',
+        centralConnection: 60, // CENTRAL_CONNECTION_REVERSE (()-->>)
+      });
+
+      expect(actualMessages[2]).toMatchObject({
+        from: 'Charlie',
+        to: 'Alice',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL (()<<-->>())
+      });
+    });
+
+    it('should handle central connections with different arrow types', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()-x() Bob: Cross message
+        Alice ()--x() Bob: Dotted cross message
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(6); // 2 addMessages + 4 central connection markers
+
+      const actualMessages = messages.filter((msg) => msg.type !== undefined && msg.from && msg.to);
+      expect(actualMessages).toHaveLength(2);
+
+      expect(actualMessages[0]).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL (()-x())
+        type: 3, // SOLID_CROSS
+      });
+
+      expect(actualMessages[1]).toMatchObject({
+        from: 'Alice',
+        to: 'Bob',
+        centralConnection: 61, // CENTRAL_CONNECTION_DUAL (()--x())
+        type: 4, // DOTTED_CROSS
+      });
+    });
+
+    it('should not break existing parsing without central connections', async () => {
+      const diagram = await Diagram.fromText(`
+        sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ->> Bob: Normal message
+        Bob -->> Alice: Normal dotted message
+        Alice -x Bob: Normal cross message
+      `);
+
+      const messages = diagram.db.getMessages();
+      expect(messages).toHaveLength(3);
+
+      messages.forEach((msg) => {
+        expect(msg.centralConnection).toBe(0); // No central connection
+      });
+
+      expect(messages[0].type).toBe(0); // SOLID (based on actual parsing)
+      expect(messages[1].type).toBe(1); // DOTTED (based on actual parsing)
+      expect(messages[2].type).toBe(3); // SOLID_CROSS
+    });
+  });
+});
+
 describe('when parsing a sequenceDiagram', function () {
   let diagram;
   beforeEach(async function () {
@@ -2058,6 +2312,36 @@ Bob->>Alice:Got it!
     expect(messages[0].from).toBe('Alice');
     expect(messages[0].to).toBe('Bob');
   });
+
+  it('1 should parse ', async () => {
+    const diagram = await Diagram.fromText(`
+    sequenceDiagram
+    actor Bob
+    actor Alice
+        Bob -|\\ Alice: Hello Alice, how are you?
+        Bob -|/ Alice: Hello Alice, how are you?
+        Bob -// Alice: Hello Alice, how are you?
+        Bob -\\\\ Alice: Hello Alice, how are you?
+        
+        Bob \\|- Alice: Hello Alice, how are you?
+        Bob /|- Alice: Hello Alice, how are you?
+        Bob //- Alice: Hello Alice, how are you?
+        Bob \\\\- Alice: Hello Alice, how are you?        
+    `);
+
+    const messages = diagram.db.getMessages();
+  });
+
+  it('2 should parse ', async () => {
+    const diagram = await Diagram.fromText(`
+    sequenceDiagram
+    actor Bob
+    actor Alice
+      Alice ()<<->>() Bob: hey?
+    `);
+
+    const messages = diagram.db.getMessages();
+  });
   describe('when parsing extended participant syntax', () => {
     it('should parse participants with different quote styles and whitespace', async () => {
       const diagram = await Diagram.fromText(`

packages/mermaid/src/diagrams/sequence/sequenceRenderer.ts

@@ -282,6 +282,49 @@ const drawNote = async function (elem: any, noteModel: NoteModel) {
   bounds.models.addNote(noteModel);
 };
 
+const drawCentralConnection = function (
+  elem: any,
+  msg: any,
+  msgModel: any,
+  diagObj: Diagram,
+  startx: number,
+  stopx: number,
+  lineStartY: number
+) {
+  const actors = diagObj.db.getActors();
+  const fromActor = actors.get(msg.from);
+  const toActor = actors.get(msg.to);
+  const fromCenter = fromActor.x + fromActor.width / 2;
+  const toCenter = toActor.x + toActor.width / 2;
+
+  const g = elem.append('g');
+
+  const drawCircle = (cx: number) => {
+    g.append('circle')
+      .attr('cx', cx)
+      .attr('cy', lineStartY)
+      .attr('r', 5)
+      .attr('width', 10)
+      .attr('height', 10);
+  };
+
+  const { CENTRAL_CONNECTION, CENTRAL_CONNECTION_REVERSE, CENTRAL_CONNECTION_DUAL } =
+    diagObj.db.LINETYPE;
+
+  switch (msg.centralConnection) {
+    case CENTRAL_CONNECTION:
+      drawCircle(toCenter);
+      break;
+    case CENTRAL_CONNECTION_REVERSE:
+      drawCircle(fromCenter);
+      break;
+    case CENTRAL_CONNECTION_DUAL:
+      drawCircle(fromCenter);
+      drawCircle(toCenter);
+      break;
+  }
+};
+
 const messageFont = (cnf) => {
   return {
     fontFamily: cnf.messageFontFamily,
@@ -367,7 +410,7 @@ async function boundMessage(_diagram, msgModel): Promise<number> {
  * @param lineStartY - The Y coordinate at which the message line starts
  * @param diagObj - The diagram object.
  */
-const drawMessage = async function (diagram, msgModel, lineStartY: number, diagObj: Diagram) {
+const drawMessage = async function (diagram, msgModel, lineStartY: number, diagObj: Diagram, msg) {
   const { startx, stopx, starty, message, type, sequenceIndex, sequenceVisible } = msgModel;
   const textDims = utils.calculateTextDimensions(message, messageFont(conf));
   const textObj = svgDrawCommon.getTextObj();
@@ -433,6 +476,9 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
     line.attr('y1', lineStartY);
     line.attr('x2', stopx);
     line.attr('y2', lineStartY);
+    if (hasCentralConnection(msg, diagObj)) {
+      drawCentralConnection(diagram, msg, msgModel, diagObj, startx, stopx, lineStartY);
+    }
   }
   // Make an SVG Container
   // Draw the line
@@ -441,7 +487,15 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
     type === diagObj.db.LINETYPE.DOTTED_CROSS ||
     type === diagObj.db.LINETYPE.DOTTED_POINT ||
     type === diagObj.db.LINETYPE.DOTTED_OPEN ||
-    type === diagObj.db.LINETYPE.BIDIRECTIONAL_DOTTED
+    type === diagObj.db.LINETYPE.BIDIRECTIONAL_DOTTED ||
+    type === diagObj.db.LINETYPE.SOLID_TOP_DOTTED ||
+    type === diagObj.db.LINETYPE.SOLID_BOTTOM_DOTTED ||
+    type === diagObj.db.LINETYPE.STICK_TOP_DOTTED ||
+    type === diagObj.db.LINETYPE.STICK_BOTTOM_DOTTED ||
+    type === diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED ||
+    type === diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED ||
+    type === diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED ||
+    type === diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED
   ) {
     line.style('stroke-dasharray', '3, 3');
     line.attr('class', 'messageLine1');
@@ -457,6 +511,51 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
   line.attr('stroke-width', 2);
   line.attr('stroke', 'none'); // handled by theme/css anyway
   line.style('fill', 'none'); // remove any fill colour
+
+  if (type === diagObj.db.LINETYPE.SOLID_TOP || type === diagObj.db.LINETYPE.SOLID_TOP_DOTTED) {
+    line.attr('marker-end', 'url(' + url + '#solidTopArrowHead)');
+  }
+  if (
+    type === diagObj.db.LINETYPE.SOLID_BOTTOM ||
+    type === diagObj.db.LINETYPE.SOLID_BOTTOM_DOTTED
+  ) {
+    line.attr('marker-end', 'url(' + url + '#solidBottomArrowHead)');
+  }
+  if (type === diagObj.db.LINETYPE.STICK_TOP || type === diagObj.db.LINETYPE.STICK_TOP_DOTTED) {
+    line.attr('marker-end', 'url(' + url + '#stickTopArrowHead)');
+  }
+  if (
+    type === diagObj.db.LINETYPE.STICK_BOTTOM ||
+    type === diagObj.db.LINETYPE.STICK_BOTTOM_DOTTED
+  ) {
+    line.attr('marker-end', 'url(' + url + '#stickBottomArrowHead)');
+  }
+
+  if (
+    type === diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE ||
+    type === diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED
+  ) {
+    line.attr('marker-start', 'url(' + url + '#solidBottomArrowHead)');
+  }
+  if (
+    type === diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE ||
+    type === diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED
+  ) {
+    line.attr('marker-start', 'url(' + url + '#solidTopArrowHead)');
+  }
+  if (
+    type === diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE ||
+    type === diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED
+  ) {
+    line.attr('marker-start', 'url(' + url + '#stickBottomArrowHead)');
+  }
+  if (
+    type === diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE ||
+    type === diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED
+  ) {
+    line.attr('marker-start', 'url(' + url + '#stickTopArrowHead)');
+  }
+
   if (type === diagObj.db.LINETYPE.SOLID || type === diagObj.db.LINETYPE.DOTTED) {
     line.attr('marker-end', 'url(' + url + '#arrowhead)');
   }
@@ -481,7 +580,18 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
       type === diagObj.db.LINETYPE.BIDIRECTIONAL_SOLID ||
       type === diagObj.db.LINETYPE.BIDIRECTIONAL_DOTTED;
 
-    if (isBidirectional) {
+    const isReverseArrowType =
+      type === diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE ||
+      type === diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED ||
+      type === diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE ||
+      type === diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED ||
+      type === diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE ||
+      type === diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED ||
+      type === diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE ||
+      type === diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED;
+
+    let x = 0;
+    if (isBidirectional || isReverseArrowType) {
       const SEQUENCE_NUMBER_RADIUS = 6;
 
       if (startx < stopx) {
@@ -489,6 +599,7 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
       } else {
         line.attr('x1', startx + SEQUENCE_NUMBER_RADIUS);
       }
+      x = 3.5;
     }
 
     diagram
@@ -498,7 +609,8 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
       .attr('x2', startx)
       .attr('y2', lineStartY)
       .attr('stroke-width', 0)
-      .attr('marker-start', 'url(' + url + '#sequencenumber)');
+      .attr('marker-start', 'url(' + url + '#sequencenumber)')
+      .attr('transform', `translate(-${x}, 0)`);
 
     diagram
       .append('text')
@@ -508,7 +620,8 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
       .attr('font-size', '12px')
       .attr('text-anchor', 'middle')
       .attr('class', 'sequenceNumber')
-      .text(sequenceIndex);
+      .text(sequenceIndex)
+      .attr('transform', `translate(-${x}, 0)`);
   }
 };
 
@@ -857,6 +970,10 @@ export const draw = async function (_text: string, id: string, _version: string,
   svgDraw.insertArrowCrossHead(diagram);
   svgDraw.insertArrowFilledHead(diagram);
   svgDraw.insertSequenceNumber(diagram);
+  svgDraw.insertSolidTopArrowHead(diagram);
+  svgDraw.insertSolidBottomArrowHead(diagram);
+  svgDraw.insertStickTopArrowHead(diagram);
+  svgDraw.insertStickBottomArrowHead(diagram);
 
   /**
    * @param msg - The message to draw.
@@ -897,6 +1014,12 @@ export const draw = async function (_text: string, id: string, _version: string,
       case diagObj.db.LINETYPE.ACTIVE_START:
         bounds.newActivation(msg, diagram, actors);
         break;
+      case diagObj.db.LINETYPE.CENTRAL_CONNECTION:
+        bounds.newActivation(msg, diagram, actors);
+        break;
+      case diagObj.db.LINETYPE.CENTRAL_CONNECTION_REVERSE:
+        bounds.newActivation(msg, diagram, actors);
+        break;
       case diagObj.db.LINETYPE.ACTIVE_END:
         activeEnd(msg, bounds.getVerticalPos());
         break;
@@ -1055,7 +1178,7 @@ export const draw = async function (_text: string, id: string, _version: string,
             createdActors,
             destroyedActors
           );
-          messagesToDraw.push({ messageModel: msgModel, lineStartY: lineStartY });
+          messagesToDraw.push({ messageModel: msgModel, lineStartY: lineStartY, msg });
           bounds.models.addMessage(msgModel);
         } catch (e) {
           log.error('error while drawing message', e);
@@ -1068,6 +1191,27 @@ export const draw = async function (_text: string, id: string, _version: string,
         diagObj.db.LINETYPE.SOLID_OPEN,
         diagObj.db.LINETYPE.DOTTED_OPEN,
         diagObj.db.LINETYPE.SOLID,
+
+        diagObj.db.LINETYPE.SOLID_TOP,
+        diagObj.db.LINETYPE.SOLID_BOTTOM,
+        diagObj.db.LINETYPE.STICK_TOP,
+        diagObj.db.LINETYPE.STICK_BOTTOM,
+
+        diagObj.db.LINETYPE.SOLID_TOP_DOTTED,
+        diagObj.db.LINETYPE.SOLID_BOTTOM_DOTTED,
+        diagObj.db.LINETYPE.STICK_TOP_DOTTED,
+        diagObj.db.LINETYPE.STICK_BOTTOM_DOTTED,
+
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE,
+        diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE,
+        diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE,
+
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED,
+
         diagObj.db.LINETYPE.DOTTED,
         diagObj.db.LINETYPE.SOLID_CROSS,
         diagObj.db.LINETYPE.DOTTED_CROSS,
@@ -1087,7 +1231,7 @@ export const draw = async function (_text: string, id: string, _version: string,
   await drawActors(diagram, actors, actorKeys, false);
 
   for (const e of messagesToDraw) {
-    await drawMessage(diagram, e.messageModel, e.lineStartY, diagObj);
+    await drawMessage(diagram, e.messageModel, e.lineStartY, diagObj, e.msg);
   }
   if (conf.mirrorActors) {
     await drawActors(diagram, actors, actorKeys, true);
@@ -1461,12 +1605,78 @@ const buildNoteModel = async function (msg, actors, diagObj) {
   return noteModel;
 };
 
+// Central connection positioning constants
+const CENTRAL_CONNECTION_BASE_OFFSET = 4;
+const CENTRAL_CONNECTION_BIDIRECTIONAL_OFFSET = 6;
+
+/**
+ * Check if a message has central connection
+ * @param msg - The message object
+ * @param diagObj - The diagram object containing LINETYPE constants
+ * @returns True if the message has any type of central connection
+ */
+const hasCentralConnection = function (msg, diagObj) {
+  const { CENTRAL_CONNECTION, CENTRAL_CONNECTION_REVERSE, CENTRAL_CONNECTION_DUAL } =
+    diagObj.db.LINETYPE;
+  return [CENTRAL_CONNECTION, CENTRAL_CONNECTION_REVERSE, CENTRAL_CONNECTION_DUAL].includes(
+    msg.centralConnection
+  );
+};
+
+/**
+ * Calculate the positioning offset for central connection arrows
+ * @param msg - The message object
+ * @param diagObj - The diagram object containing LINETYPE constants
+ * @param isArrowToRight - Whether the arrow is pointing to the right
+ * @returns The offset to apply to startx position
+ */
+const calculateCentralConnectionOffset = function (msg, diagObj, isArrowToRight) {
+  const { CENTRAL_CONNECTION_REVERSE, CENTRAL_CONNECTION_DUAL, BIDIRECTIONAL_SOLID } =
+    diagObj.db.LINETYPE;
+
+  let offset = 0;
+
+  if (
+    msg.centralConnection === CENTRAL_CONNECTION_REVERSE ||
+    msg.centralConnection === CENTRAL_CONNECTION_DUAL
+  ) {
+    offset += CENTRAL_CONNECTION_BASE_OFFSET;
+  }
+
+  if (msg.centralConnection === CENTRAL_CONNECTION_DUAL && msg.type === BIDIRECTIONAL_SOLID) {
+    offset += isArrowToRight ? 0 : -CENTRAL_CONNECTION_BIDIRECTIONAL_OFFSET;
+  }
+
+  return offset;
+};
+
 const buildMessageModel = function (msg, actors, diagObj) {
   if (
     ![
       diagObj.db.LINETYPE.SOLID_OPEN,
       diagObj.db.LINETYPE.DOTTED_OPEN,
       diagObj.db.LINETYPE.SOLID,
+
+      diagObj.db.LINETYPE.SOLID_TOP,
+      diagObj.db.LINETYPE.SOLID_BOTTOM,
+      diagObj.db.LINETYPE.STICK_TOP,
+      diagObj.db.LINETYPE.STICK_BOTTOM,
+
+      diagObj.db.LINETYPE.SOLID_TOP_DOTTED,
+      diagObj.db.LINETYPE.SOLID_BOTTOM_DOTTED,
+      diagObj.db.LINETYPE.STICK_TOP_DOTTED,
+      diagObj.db.LINETYPE.STICK_BOTTOM_DOTTED,
+
+      diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE,
+      diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE,
+      diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE,
+      diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE,
+
+      diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED,
+      diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED,
+      diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED,
+      diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED,
+
       diagObj.db.LINETYPE.DOTTED,
       diagObj.db.LINETYPE.SOLID_CROSS,
       diagObj.db.LINETYPE.DOTTED_CROSS,
@@ -1484,6 +1694,8 @@ const buildMessageModel = function (msg, actors, diagObj) {
   let startx = isArrowToRight ? fromRight : fromLeft;
   let stopx = isArrowToRight ? toLeft : toRight;
 
+  // Apply central connection positioning adjustments
+  startx += calculateCentralConnectionOffset(msg, diagObj, isArrowToRight);
   // As the line width is considered, the left and right values will be off by 2.
   const isArrowToActivation = Math.abs(toLeft - toRight) > 2;
 
@@ -1517,7 +1729,30 @@ const buildMessageModel = function (msg, actors, diagObj) {
      * Shorten the length of arrow at the end and move the marker forward (using refX) to have a clean arrowhead
      * This is not required for open arrows that don't have arrowheads
      */
-    if (![diagObj.db.LINETYPE.SOLID_OPEN, diagObj.db.LINETYPE.DOTTED_OPEN].includes(msg.type)) {
+    if (
+      ![
+        diagObj.db.LINETYPE.SOLID_OPEN,
+        diagObj.db.LINETYPE.DOTTED_OPEN,
+
+        diagObj.db.LINETYPE.STICK_TOP,
+        diagObj.db.LINETYPE.STICK_BOTTOM,
+
+        diagObj.db.LINETYPE.STICK_TOP_DOTTED,
+        diagObj.db.LINETYPE.STICK_BOTTOM_DOTTED,
+
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED,
+
+        diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE,
+        diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE,
+
+        diagObj.db.LINETYPE.STICK_ARROW_TOP_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.STICK_ARROW_BOTTOM_REVERSE_DOTTED,
+
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE,
+      ].includes(msg.type)
+    ) {
       stopx += adjustValue(3);
     }
 
@@ -1525,9 +1760,14 @@ const buildMessageModel = function (msg, actors, diagObj) {
      * Shorten start position of bidirectional arrow to accommodate for second arrowhead
      */
     if (
-      [diagObj.db.LINETYPE.BIDIRECTIONAL_SOLID, diagObj.db.LINETYPE.BIDIRECTIONAL_DOTTED].includes(
-        msg.type
-      )
+      [
+        diagObj.db.LINETYPE.BIDIRECTIONAL_SOLID,
+        diagObj.db.LINETYPE.BIDIRECTIONAL_DOTTED,
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE_DOTTED,
+        diagObj.db.LINETYPE.SOLID_ARROW_TOP_REVERSE,
+        diagObj.db.LINETYPE.SOLID_ARROW_BOTTOM_REVERSE,
+      ].includes(msg.type)
     ) {
       startx -= adjustValue(3);
     }

packages/mermaid/src/diagrams/sequence/svgDraw.js

@@ -1709,6 +1709,77 @@ const _drawMenuItemTextCandidateFunc = (function () {
   };
 })();
 
+/**
+ * Setup arrow head and define the marker. The result is appended to the svg.
+ *
+ * @param elem
+ */
+export const insertSolidTopArrowHead = function (elem) {
+  elem
+    .append('defs')
+    .append('marker')
+    .attr('id', 'solidTopArrowHead')
+    .attr('refX', 7.9)
+    .attr('refY', 7.25)
+    .attr('markerUnits', 'userSpaceOnUse')
+    .attr('markerWidth', 12)
+    .attr('markerHeight', 12)
+    .attr('orient', 'auto-start-reverse')
+    .append('path')
+    .attr('d', 'M 0 0 L 10 8 L 0 8 z'); // this is actual shape for arrowhead
+};
+
+export const insertSolidBottomArrowHead = function (elem) {
+  elem
+    .append('defs')
+    .append('marker')
+    .attr('id', 'solidBottomArrowHead')
+    .attr('refX', 7.9)
+    .attr('refY', 0.75)
+    .attr('markerUnits', 'userSpaceOnUse')
+    .attr('markerWidth', 12)
+    .attr('markerHeight', 12)
+    .attr('orient', 'auto-start-reverse')
+    .append('path')
+    .attr('d', 'M 0 0 L 10 0 L 0 8 z');
+};
+
+export const insertStickTopArrowHead = function (elem) {
+  elem
+    .append('defs')
+    .append('marker')
+    .attr('id', 'stickTopArrowHead')
+    .attr('refX', 7.5)
+    .attr('refY', 7)
+    .attr('markerUnits', 'userSpaceOnUse')
+    .attr('markerWidth', 12)
+    .attr('markerHeight', 12)
+    .attr('orient', 'auto-start-reverse')
+    .append('path')
+    .attr('d', 'M 0 0 L 7 7')
+    .attr('stroke', 'black')
+    .attr('stroke-width', 1.5)
+    .attr('fill', 'none');
+};
+
+export const insertStickBottomArrowHead = function (elem) {
+  elem
+    .append('defs')
+    .append('marker')
+    .attr('id', 'stickBottomArrowHead')
+    .attr('refX', 7.5)
+    .attr('refY', 0)
+    .attr('markerUnits', 'userSpaceOnUse')
+    .attr('markerWidth', 12)
+    .attr('markerHeight', 12)
+    .attr('orient', 'auto-start-reverse')
+    .append('path')
+    .attr('d', 'M 0 7 L 7 0')
+    .attr('stroke', 'black')
+    .attr('stroke-width', 1.5)
+    .attr('fill', 'none');
+};
+
 export default {
   drawRect,
   drawText,
@@ -1731,4 +1802,8 @@ export default {
   getNoteRect,
   fixLifeLineHeights,
   sanitizeUrl,
+  insertSolidTopArrowHead,
+  insertSolidBottomArrowHead,
+  insertStickTopArrowHead,
+  insertStickBottomArrowHead,
 };

packages/mermaid/src/diagrams/sequence/types.ts

@@ -35,6 +35,7 @@ export interface Message {
   type?: number;
   activate?: boolean;
   placement?: string;
+  centralConnection?: number;
 }
 
 export interface AddMessageParams {
@@ -50,6 +51,8 @@ export interface AddMessageParams {
     | 'destroyParticipant'
     | 'activeStart'
     | 'activeEnd'
+    | 'centralConnection'
+    | 'centralConnectionReverse'
     | 'addNote'
     | 'addLinks'
     | 'addALink'

packages/mermaid/src/docs/config/faq.md

@@ -1,6 +1,6 @@
 # Frequently Asked Questions
 
-1. [How to add title to flowchart?](https://github.com/mermaid-js/mermaid/issues/556#issuecomment-363182217)
+1. [How to add title to flowchart?](https://github.com/mermaid-js/mermaid/issues/1433#issuecomment-1991554712)
 1. [How to specify custom CSS file?](https://github.com/mermaidjs/mermaid.cli/pull/24#issuecomment-373402785)
 1. [How to fix tooltip misplacement issue?](https://github.com/mermaid-js/mermaid/issues/542#issuecomment-3343564621)
 1. [How to specify gantt diagram xAxis format?](https://github.com/mermaid-js/mermaid/issues/269#issuecomment-373229136)

packages/mermaid/src/docs/syntax/entityRelationshipDiagram.md

@@ -151,35 +151,6 @@ erDiagram
     PERSON many(0) optionally to 0+ NAMED-DRIVER : is
 ```
 
-### Aggregation
-
-Aggregation represents a "has-a" relationship where the part can exist independently of the whole. This is different from composition, where the part cannot exist without the whole. Aggregation relationships are rendered with hollow diamond markers at the endpoints.
-
-| Value |      Alias for       | Description                    |
-| :---: | :------------------: | ------------------------------ |
-|  <>   |    _aggregation_     | Basic aggregation (solid line) |
-| <>..  | _aggregation-dashed_ | Dashed aggregation line        |
-
-**Examples:**
-
-```mermaid-example
-erDiagram
-    DEPARTMENT <> EMPLOYEE : contains
-    PROJECT <>.. TASK : manages
-    TEAM <> MEMBER : consists_of
-```
-
-In these examples:
-
-- `DEPARTMENT <> EMPLOYEE` shows that a department contains employees (aggregation)
-- `PROJECT <>.. TASK` shows that a project manages tasks (dashed aggregation)
-- `TEAM <> MEMBER` shows that a team consists of members (aggregation)
-
-**Aggregation vs Association**
-
-- **Aggregation** (`<>`): "Has-a" relationship where parts can exist independently
-- **Association** (`||--`, `}o--`): General relationship between entities
-
 ### Attributes
 
 Attributes can be defined for entities by specifying the entity name followed by a block containing multiple `type name` pairs, where a block is delimited by an opening `{` and a closing `}`. The attributes are rendered inside the entity boxes. For example:

packages/mermaid/src/docs/syntax/sequenceDiagram.md

@@ -216,7 +216,11 @@ Messages can be of two displayed either solid or with a dotted line.
 [Actor][Arrow][Actor]:Message text
 ```
 
-There are ten types of arrows currently supported:
+Lines can be solid or dotted, and can end with various types of arrowheads, crosses, or open arrows.
+
+#### Supported Arrow Types
+
+**Standard Arrow Types**
 
 | Type     | Description                                          |
 | -------- | ---------------------------------------------------- |
@@ -231,6 +235,49 @@ There are ten types of arrows currently supported:
 | `-)`     | Solid line with an open arrow at the end (async)     |
 | `--)`    | Dotted line with a open arrow at the end (async)     |
 
+**Half-Arrows (v<MERMAID_RELEASE_VERSION>+)**
+
+The following half-arrow types are supported for more expressive sequence diagrams. Both solid and dotted variants are available by increasing the number of dashes (`-` → `--`).
+
+---
+
+| Type    | Description                                          |
+| ------- | ---------------------------------------------------- |
+| `-\|\`  | Solid line with top half arrowhead                   |
+| `--\|\` | Dotted line with top half arrowhead                  |
+| `-\|/`  | Solid line with bottom half arrowhead                |
+| `--\|/` | Dotted line with bottom half arrowhead               |
+| `/\|-`  | Solid line with reverse top half arrowhead           |
+| `/\|--` | Dotted line with reverse top half arrowhead          |
+| `\\-`   | Solid line with reverse bottom half arrowhead        |
+| `\\--`  | Dotted line with reverse bottom half arrowhead       |
+| `-\\`   | Solid line with top stick half arrowhead             |
+| `--\\`  | Dotted line with top stick half arrowhead            |
+| `-//`   | Solid line with bottom stick half arrowhead          |
+| `--//`  | Dotted line with bottom stick half arrowhead         |
+| `//-`   | Solid line with reverse top stick half arrowhead     |
+| `//--`  | Dotted line with reverse top stick half arrowhead    |
+| `\\-`   | Solid line with reverse bottom stick half arrowhead  |
+| `\\--`  | Dotted line with reverse bottom stick half arrowhead |
+
+## Central Connections (v<MERMAID_RELEASE_VERSION>+)
+
+Mermaid sequence diagrams support **central lifeline connections** using a `()`.
+This is useful to represent messages or signals that connect to a central point, rather than from one actor directly to another.
+
+To indicate a central connection, append `()` to the arrow syntax.
+
+#### Basic Syntax
+
+```mermaid-example
+sequenceDiagram
+    participant Alice
+    participant John
+    Alice->>()John: Hello John
+    Alice()->>John: How are you?
+    John()->>()Alice: Great!
+```
+
 ## Activations
 
 It is possible to activate and deactivate an actor. (de)activation can be dedicated declarations:

packages/mermaid/src/mermaid.spec.ts

@@ -207,7 +207,7 @@ describe('when using mermaid and ', () => {
         [Error: Parse error on line 2:
         ...equenceDiagramAlice:->Bob: Hello Bob, h...
         ----------------------^
-        Expecting 'SOLID_OPEN_ARROW', 'DOTTED_OPEN_ARROW', 'SOLID_ARROW', 'BIDIRECTIONAL_SOLID_ARROW', 'DOTTED_ARROW', 'BIDIRECTIONAL_DOTTED_ARROW', 'SOLID_CROSS', 'DOTTED_CROSS', 'SOLID_POINT', 'DOTTED_POINT', got 'TXT']
+        Expecting '()', 'SOLID_OPEN_ARROW', 'DOTTED_OPEN_ARROW', 'SOLID_ARROW', 'SOLID_ARROW_TOP', 'SOLID_ARROW_BOTTOM', 'STICK_ARROW_TOP', 'STICK_ARROW_BOTTOM', 'SOLID_ARROW_TOP_DOTTED', 'SOLID_ARROW_BOTTOM_DOTTED', 'STICK_ARROW_TOP_DOTTED', 'STICK_ARROW_BOTTOM_DOTTED', 'SOLID_ARROW_TOP_REVERSE', 'SOLID_ARROW_BOTTOM_REVERSE', 'STICK_ARROW_TOP_REVERSE', 'STICK_ARROW_BOTTOM_REVERSE', 'SOLID_ARROW_TOP_REVERSE_DOTTED', 'SOLID_ARROW_BOTTOM_REVERSE_DOTTED', 'STICK_ARROW_TOP_REVERSE_DOTTED', 'STICK_ARROW_BOTTOM_REVERSE_DOTTED', 'BIDIRECTIONAL_SOLID_ARROW', 'DOTTED_ARROW', 'BIDIRECTIONAL_DOTTED_ARROW', 'SOLID_CROSS', 'DOTTED_CROSS', 'SOLID_POINT', 'DOTTED_POINT', got 'TXT']
       `);
     });