Bidirectional OO-LD <-> DLite data model converter #115

Convert between OO-LD schemas and DLite data models.

Spec-side siblings: OO-LD/oold-schema#17 (JSON-SCHEMA for DLite data models, incl. soft5 vs soft7 and property dimensionality) and OO-LD/oold-schema#107 (QuantityValue as a base building block).

cc @jesper-friis

Mapping

• DLite entity to object schema, DLite properties to schema properties
• Entity URI to $id and the type IRI in the @context
• Property type and shape to JSON Schema types and nested arrays
• Property unit to the OO-LD quantity value representation

Expressible with standard keywords: entity identity, property names, scalar types, nesting depth
of an array, and required or optional status. Needing an x- vendor annotation: the named
dimensions and their descriptions, the explicit rank, and the cross-property axis linkage, since
DLite guarantees that the second axis of temperature is the same dimension as the only axis of
depth while nested arrays assert nothing of the kind. Units may also need one, depending on how
OO-LD/oold-schema#107 settles.

Open questions

• Which DLite format to target, soft5 or soft7. JSON-SCHEMA for DLite data models oold-schema#17 notes the current README suggestion is soft7 based but soft5 may fit better
• Where dimension identity should live: an x-oold-* keyword carrying the named dimensions, or the coordinate system approach discussed in JSON-SCHEMA for DLite data models oold-schema#17, which also relates axes to the properties that define their values
• Whether coordinate system transformations are in scope here or need to be settled in the spec first
• Whether a lossy one-way conversion is acceptable as a first step