Add design decisions document

[xamde]

I would like to add a somewhat structured design decision document

[devhelpr]

Very good idea to have this document, and I just add my remarks in one comment:

• perhaps use json schema only as a reference format just as we want to use typescript. The spec itself could be formal described in markdown with tables etc.

• structures:

  • ports

  • are part of nodes from my perspective. and depending on an app, these might not be freely configurable and specified by the node-types themselves which ports are available (at least that's the case in my own tool :-) )

  • have properties of their own but this is probably implementation specific:

    • position
    • input/output
    • constraints : max connections, allowed type to connect

  • arrows

    • are part of edges

  • edges

    • do we only support a basic straight line in ocwg spec itself? or do we have an edge-line-type which can be:
      • line
      • quadratic curve
      • cubic curve
      • multi line segment (path?)
    • edges can have different arrow types on either side or none at all

  • what do you mean with roles? (it is mentioned under structures)

• list of types of infinite canvas applications we want to support

  • white board
  • node and wire visual programming
  • diagram apps
  • state machines
  • systems that use auto-layout like mermaid / plantuml

• should we put the sample applications formats in a different file?

• visual fidelty: we should not just target browsers but also desktop/mobile apps and/or rendering using none html/text systems like webgl/opengl etc