[DDI 4] - JSON Schema - type self-references

[duffgui]

Hi,

We generated several years ago a Java model from the 3.2 schema, then from the 3.3 schema. We have been trying to do the same from the DDI 4 JSON Schema and have hit a roadblock. Indeed, there are nested and recursive references: for example, LocationValueTypes that points to other LocationValueTypes, which themselves point to LocationValueTypes, etc. Therefore, during the generation process in Java, a StackOverflowException is raised.

We wonder whether or not these nested and recursive self-references are intentional:

• If not, can the schema be updated?
• If so, do you have some recommendations to prevent the StackOverflowException to occur?

Thank you very much for your assistance.

[wlthomas]

I checked the specific item you noted LocationValueType. In 3.3 none of the internal parts are directly LocationValue. ComponentParts and ImmediateParent types are LocationValueBundle (a collection of LocationValues that are in the role of component part or immediate parent.
SupercedesLocationValue and PrecedesLocationValue are both RelatedLocationValueReferenceTypes which are extensions of reference which adds an object to define whether the full or partial location fills that role.
I know there was some problems with extended reference types as the conversion into the 4.0 format took place. These last two appear to have been converted to a set of objects which reflect the full and partial status:

SupersedesLocationValue | LocationValueType | 0 | n | Provides a reference to the LocationValue or Values that the current LocationValue supersedes fully. For example, if the LocationValue was the State of North Dakota as defined in 1890 it would supersede the LocationValue for Dakota Territory (1861-1889) as a description of "part" of that Territory.

SupersedesPartialLocationValue | LocationValueType | 0 | n | Provides a reference to the LocationValue or Values that the current LocationValue supersedes partially. For example, if the LocationValue was the State of North Dakota as defined in 1890 it would supersede the LocationValue for Dakota Territory (1861-1889) as a description of "part" of that Territory.

PrecedesLocationValue | LocationValueType | 0 | n | Provides a reference to the LocationValue or Values that the current LocationValue immediately precedes fully. For example, if the LocationValue was the Dakota Territory (1861-1889) preceded the State of North Dakota and the State of South Dakota as defined in 1890. The Dakota Territory provided "part" of its area in the creation of each new LocationValue.

PrecedesPartialLocationValue | LocationValueType | 0 | n | Provides a reference to the LocationValue or Values that the current LocationValue immediately precedes partially. For example, if the LocationValue was the Dakota Territory (1861-1889) preceded the State of North Dakota and the State of South Dakota as defined in 1890. The Dakota Territory provided "part" of its area in the creation of each new LocationValue.

So the model seems correct.

[duffgui]

Thanks for your quick response.

I understand from your examples, that in the JSON Schema, as opposed to the XSD schema, these are not extensions of reference, but direct LocationValueType. That might be a side effect of the JSON Schema serialisation, and this is precisely what causes the Java Exception on our side.