[question] How should the extension of core schema's be specified?

[devhelpr]

Hi,

I've made a very early export from codeflowcanvas.io to OCWG (currently just the nodes), and I wondered how the schemas section in the spec works?

See below a very simple export. this is just a single node which is exported and it uses a node schema @ocwg/code-flow-canvas-node which extends @ocwg/rectangle. How should that be specified in the schemas section?

I probably should have used a different schema for my node type, something like @codeflowcanvas/node

{
  "schema_version": "0.1",
  "nodes": {
    "shape:8fac6770-b623-4d68-8d74-311bb2700b7e": {
      "id": "shape:8fac6770-b623-4d68-8d74-311bb2700b7e",
      "schema": "@ocwg/code-flow-canvas-node",
      "schema_version": "0.1",
      "x": 120.87079934103329,
      "y": -264.70281730767437,
      "properties": {
        "width": 199.99997425913452,
        "height": 111.99999198708119,
        "nodeInfo": {
          "type": "expression",
          "formValues": {
            "expression": "42",
            "inputType": "number"
          },
          "taskType": "expression"
        }
      },
      "fallback": "expression\n42"
    }
  },
  "relations": {},
  "schemas": {
    "@ocwg/code-flow-canvas-node": "@ocwg/rectangle"
  }
}

you can play around with this export here : demo.codeflowcanvas.io/ocwg .. please try on desktop and use one of the example flows from the dropdown on the rightside of the topmenu. The export appears on a floating div on the bottom right and is updated when making changes to the canvas.

Kind regards,
Maikel

[xamde]

@devhelpr Here https://www.w3.org/TR/cooluris/#oldweb (just section 2, the other sections are typically semweb over-ambitious :-) ) explains how one URL can serve both HTML and technical specs (here RDF, but we would use JSON schema)

[devhelpr]

I've been reading the above and json-schema as well: If I understand correctly, then this might be closer:

{
  "schema_version": "0.1",
  "nodes": [
    {
      "id": "shape:823f6164-79ef-47c5-9549-5dc12eb0d62b",
      "schema": "@code-flow-canvas/node",
      "schema_version": "0.1",
      "x": 521.1098165923908,
      "y": -210.65675806881544,
      "properties": {
        "width": 200.00003545442723,
        "height": 112.00003403407696,
        "@code-flow-canvas/node-properties": {
          "type": "expression",
          "formValues": {
            "expression": "input",
            "inputType": "number"
          },
          "taskType": "expression"
        }
      },
      "fallback": "expression\ninput"
    },
    {
      "id": "shape:56d448f5-bcd3-4958-b676-27a4e3f7d1da",
      "schema": "@code-flow-canvas/node",
      "schema_version": "0.1",
      "x": 82.67665503888207,
      "y": -201.84272012503598,
      "properties": {
        "width": 200.00003545442723,
        "height": 112.00003403407696,
        "@code-flow-canvas/node-properties": {
          "type": "expression",
          "formValues": {
            "expression": "1",
            "inputType": "number"
          },
          "taskType": "expression"
        }
      },
      "fallback": "expression\n1"
    },
    {
      "id": "connection:33e0e6be-3104-454e-b3a4-d5bcdc78e6d9",
      "schema": "@code-flow-canvas/connection",
      "schema_version": "0.1",
      "x": 282.6766904933093,
      "y": -145.8427031079975,
      "properties": {
        "width": 0,
        "height": 0,
        "@code-flow-canvas/node-properties": {},
        "start": {
          "connected_to": "shape:56d448f5-bcd3-4958-b676-27a4e3f7d1da",
          "port_name": "output"
        },
        "end": {
          "connected_to": "shape:823f6164-79ef-47c5-9549-5dc12eb0d62b",
          "port_name": "input"
        }
      },
      "fallback": "connection"
    }
  ],
  "relations": [],
  "schemas": {
    "@code-flow-canvas/node": {
      "$schema": "https://www.canvasprotocol.org/schema/draft/2024-06/@ocwg/rectangle",
      "$id": "https://demo.codeflowcanvas.io/schema/draft/2024-07/@code-flow-canvas/node",
      "properties": {
        "@code-flow-canvas/node-properties": {
          "type": "object"
        }
      }
    },
    "@code-flow-canvas/connection": {
      "$schema": "https://www.canvasprotocol.org/schema/draft/2024-06/@ocwg/arrow",
      "$id": "https://demo.codeflowcanvas.io/schema/draft/2024-07/@code-flow-canvas/connection",
      "properties": {
        "@code-flow-canvas/node-properties": {
          "type": "object"
        },
        "start": {
          "type": "object",
          "properties": {
            "connected_to": {
              "type": "string"
            },
            "port_name": {
              "type": "string"
            }
          }
        },
        "end": {
          "type": "object",
          "properties": {
            "connected_to": {
              "type": "string"
            },
            "port_name": {
              "type": "string"
            }
          }
        }
      }
    }
  }
}

The schema's for @code-flow-canvas are placed inline, and specify from which schema these extend. The schema definitions should also be downloadable from the url's specified in $schema and $id.

In the nodes themselves , currently "schema": "@code-flow-canvas/node" is used. But I wonder if this (and the schemas section) needs to be replaced with $ref and $defs (see https://json-schema.org/understanding-json-schema/structuring#dollarref ) ?

[devhelpr]

I've been thinking a bit more about this and about the input we've got from gtlf regarding extending OCWG, and got some more questions:

• in the current spec only the nodes and relations were made extendable via the schemas property on root level. As far as I can see json-schema doesn't have a way to reference external schema's from a json document and doesn't have a way to add inline schema's in json documents. So, how are going to enforce this? In applications that support OCWG you could build this in anyway if we document this correctly as a requirement when implementing OCWG.
• If I understand correctly , in the gltf format everything can be extended and there exists an extension registry https://github.com/KhronosGroup/glTF/blob/main/extensions/README.md .. will OCWG also work like this with a registry? and if so.. do applications that support OCWG will need to register their own custom node schemas? I doubt that other applications will support these node schema's... for example : a visual programming system that supports OCWG will have their own custom node schema's for it's node-types with behavior attached.. a whiteboard application that imports the visual programming system's OCWG export will probably never implement it's behavior (but only keep its properties).

[jessmartin]

Extensions are now well-defined.