Define Trestle OSCAL extensions in a language agnostic way

[jpower432]

Issue description / feature objectives

trestle extends OSCAL through the OSCAL properties to capture rule information. This rule data is being used in multiple codebases in different programming languages. To ensure the these implementations don't diverge, defining this information in a language agnostic way would help validate the implementations.

Caveats / Assumptions

• This may require investigation into external constraints

Completion Criteria

• Define trestle Rule OSCAL property and associated properties

[butler54]

I think you are going to need to define these in metaschema?

[butler54]

@vikas-agarwal76 discussion: We need to be clearer about documenting these extensions and why.

[jpower432]

Yes @butler54. I was thinking we might look at defining metaschema constraints to define the extensions https://github.com/usnistgov/metaschema/blob/develop/schema/xml/metaschema-meta-constraints.xsd.