Feature: Allow reusable sdfProperty types

[mjkoster]

sdfProperty should allow reusable types with standalone sdfproperty definitions (outside sdfObject) and sdfProperty allowed as the target of sdfRef within an sdfProperty definition

[cabo]

Reusable types is currently done with sdfData. Are we missing anything with this mechanism?
What is the difference between sdfData and sdfProperty (syntactically, no difference in SDF 1.0)?

[akeranen]

I think we need to experiment with this feature more to see what (if any) is missing from 1.0.

[akeranen]

As discussed in the interim today, we should consider different levels of description. The generic re-usable property/data definition could have generic description but then you could have a detailed description in the context of the use. For example "level" property used for both audio buzzer and light dimmer.

[mjkoster]

One reason is for more natural modeling of the IPSO reusable Resource Types. I suppose we could map the IPSO reusable Resource types to sdfData types, but the preference was to define reusable sdfProperty types.

The use case for compound sdfProperty types is also a case of reuse of a sdfProperty definition inside another.

The sdfData definitions are meant to enable reusable semantics+ data shape constraints in both sdfProperty definitions and as sdfInputData or sdfOutputData in sdfAction and sdfEvent definitions.

[mjkoster]

This issue has been resolved by allowing an sdfProperty definition to be reused by an sdfProperty declaration, and allowing definitions of sdfProperty to occur at the root level of a namespace.