Schema change / purl-type-definition: Add enum for namespace values

[mjherzog]

This issue is intended to raise the visibility and documentation of a proposed addition to the namespace component in purl-type-definition-schema.json from its introduction in the PR below which is focused on the use of valid/known namespace values for deb and rpm package types:

• adding enumeration to the namespace field; adding enums for deb/rpm #678

The context is that purl-type-definition-schema-v1.0.json has been frozen in the form that has been submitted to Ecma/TC54 for publication as the PURL 1.0 standard. In this context any normative change to purl-type-definition-schema.json should be approved by TC54/TG2 and tracked as a future change for the PURL standard.

The proposal is to add a property to the namespace definition as:

 "registered_values": {
          "title": "Registered values",
          "description": "Optional set of regjstered namespace values for this package type. If provided, the namespace value should be one of these.",
          "type": "array",
          "items": {
            "type": "string"
          },
          "uniqueItems": true
        }

NB - I replaced "known" from the PR with "registered" where registered means included in the PURL type definition file.

PR #678 did not include any updates to test files so there is an open question about the expected validation behavior for a PURL with a namespace value that is not in the list of registered values. We should at a minimum agree on how to document the expected validation behavior if:

• A package type implements registered values for its namespace component and
• An otherwise valid PURL includes a namespace value that is not in the list of registered values.

A likely scenario is that the PURL should be validated with a warning or other message that the namespace is not registered, but this requires discussion and may require an enhancement to purl-test-schema.json to handle exception severity levels - e.g., error / warning / info instead of just expected_failure = true or false.

[mjherzog]

• See also Schema change / purl-test: Add validation tests #692 proposing a new test-type of validation with error/warning/info messages.

[pombredanne]

I like this. Of note we should also ask that the array of values is sorted, but I cannot find a way to enforce that in a JSON schema.

For the validation, I suggest we have a warning for non-registered value.

Also we likely can expand this approach to qualifiers: there we would have a definition for that property that we would reuse in the qualifiers for the list of registered_values for a registered key (

purl-spec/schemas/purl-type-definition.schema-1.0.json

Line 239 in 31fd179

"key": {

)