Proposal to use the Python Generator for CDM 5.x and 6.x

[dschwartznyc]

Background

The new Python generator will be used for CDM 7.

Should it be used for CDM 5.x and 6.x?

Proposal

To recap the new generator implements the agreed serialization format and adds support for:

• Rune features such as metadata missing from earlier versions of the generator
• Recursive type definitions (i.e. type A has an attribute of type B and type B has an attribute of type A); and
• In a future release, function generation.

Compatibility

From a CDM perspective, we believe that the support for metadata and any other new features of the DSL (such as the choice operator) is all non-breaking.

The downside of using the new generator for earlier versions of CDM is that it will serialize in a format inconsistent with that produced by the Java implementations for those same versions. We believe this to be an acceptable difference since CDM 7 standardizes the format and the lack of metadata support in the current Python generator implies that the serialization formats already diverge.

Release

CDM 5.x and 6.x

Additional Context

Directed to the TAWG

[dschwartznyc]

As requested, a comparison of impact of the current and new Python generators on CDM 5 and 6.

Feature	CDM Version	Current Generator	New Generator
Meta Data Support	5	❌	✔️
	6	❌	✔️
Support for Recursive Types	5	not used	not used
	6	❌	✔️
Support for Functions (*)	5	❌	✔️
	6	❌	✔️

(*) When provided for CDM 7

In summary, preventing this update will leave major gaps for the Python versions of CDM 5 and 6 and has little to no impact on compatibility.

[llynhiavu]

Sounds good to me (at first glance, mostly benefits to be gained)

On the downside, would the serialization difference only manifest if a CDM 5/6 Java implementation were to exchange data with a CDM Python implementation? if my question even makes sense.

[dschwartznyc]

@llynhiavu - thanks for feedback.

You are correct that the change will create a challenge for the exchange of data for CDM 5 and 6 between systems using Java and Python but the issue will be no worse than exists with the current Python generator. Keeping in mind that the serialization standard has just been established, JSON created and readable by a Java implementation of CDM 5 or 6 may not be understood by the equivalent current Python version of CDM.