Spec currently allows both the use of definition_type/definition properties and extensions with marking-definitions

[rpiazza]

The following is valid as the spec is currently written:

{
			"type": "marking-definition",
			"spec_version": "2.1",
			"id": "marking-definition--b58d6a2a-f14a-4994-af70-69156cd48190",
			"created": "2022-10-25T13:51:56.797459Z",
			"definition_type": "statement",
			"definition": {
				"statement": "U//FOUO"
			},
			"name": "UNCLASSIFIED//FOR OFFICIAL USE ONLY",
			"extensions": {
				"extension-definition--3a65884d-005a-4290-8335-cb2d778a83ce": {
					"control_set": {
						"classification": "U",
						"formal_determination": [
							"FOUO"
						]
					},
					"create_date_time": "2022-10-25T13:51:56.796458Z",
					"extension_type": "property-extension",
					"identifier": "isa:guide.19001.ACS3-2b51e0d7-e3de-43cf-81ac-09e21ee0ff5d",
					"policy_reference": "urn:isa:policy:acs:ns:v3.0?privdefault=deny&sharedefault=permit",
					"responsible_entity_custodian": "USA.USG"
				}


			}
		}

This marking-definition object contains both statement and ACS marking information, as an extension. The spec says:

If the extensions property is not present, this (definition-type) property MUST be present.

But it doesn’t say the opposite (i.e., if the definition-type is present, then the extension property MUST NOT be present).

One marking-definition object shouldn’t contain information about more than one marking definition type, since they could be contradictory. This should be corrected in the spec