Model: Extension
There is information about a type that is useful for certain cases, but at the same time is not needed in every case. The data model of the types should remain lean and not be overloaded. Nevertheless, future changes and new functionalities should be made possible. However, this should be done in a way without becoming incompatible. This extended information is called extensions.
An extension consists of two fields. On the one hand the name of the extension and on the other hand a field with unstructured data in JSON format. This means that the data model of the extension is not specified. At the same time, however, it is possible to provide any conceivable information. Because a JSON value is used, any complex and nested information is possible. It is possible to deserialize the JSON value into a concrete data model.
An example of an extension is the information on how a flow editor should draw a shape of an entity type. The extension is called "flow_shape" and contains information about the color, size, label and alignment of the shape. This example shows that an extension can potentially contain very complex data structures and at the same time that an extension covers a case that is not relevant in all cases. For example, if the "Flow Editor" plugin is not installed or not activated, the extension is present but not used.
Data Model
| Field | DataType | Description |
|---|---|---|
| Namespace | String | The namespace |
| Name | String | The name of the extension |
| Extension | JSON | The extension as schema-less JSON. |
ER Diagram
erDiagram
Extension {
string namespace
string name
JSON extension
}
Entity-Type ||--}o Extension : has
Relation-Type ||--}o Extension : has
Flow-Type ||--}o Extension : has
Property-Type ||--}o Extension : has
Entity-Instance ||--}o Extension : has
Relation-Instance ||--}o Extension : has
List of known extensions
| Extension | Description |
|---|---|
| dublin-core | Meta data |
| flow_editor_palette | An entry for the palette of the flow editor |
| flow_editor_shape | Definition of the shape of an entity instance in the flow editor |
| type_graph_shape | Definition of the shape of an entity type in the type graph |
| instance_graph_shape | Definition of the shape of an entity instance of in the instance graph |
Extension dublin_core
{
"name": "dublin-core",
"extension":{
"title": "Decrement number",
"subject": "Decrement number",
"creator": "Hanack"
}
}
Extension flow_editor_palette
{
"name": "flow_editor_palette",
"extension": {
"content": "Decrement",
"styles": {
"font-family": "Fira Code",
"font-size": "12px",
"padding": "5px"
}
}
}
Extension flow_editor_shape
{
"name": "flow_editor_shape",
"extension": {
"width": 200,
"socket": {
"width": 60,
"height": 30,
"offset": 5
},
"offset": {
"top": "socket.height",
"bottom": "socket.height"
},
"elements": {
"title": {
"show": true,
"type": "text",
"content": "element.description",
"position": {
"left": 0,
"top": 0,
"width": "shape.width",
"height": "socket.height"
},
"styles": {
"font-size": "12px",
"color": "black"
}
},
"symbol": {
"show": true,
"type": "text",
"content": "--",
"position": {
"left": 0,
"top": 0,
"width": "shape.width",
"height": "shape.height"
},
"styles": {
"fill": "steelblue",
"font-size": "80px",
"font-family": "Fira Code"
}
},
"id": {
"show": true,
"type": "text",
"content": "shape.id",
"position": {
"left": 0,
"top": "shape.height-socket.height",
"width": "shape.width",
"height": "socket.height"
},
"styles": {
"font-size": "9px",
"color": "black"
}
}
}
}
}