DEXPI Validation Error

[kommerzienrat]

Constraint AASd-127 incorrectly rejected valid DEXPI RelationshipElement structure

Description

The AAS validator rejects valid DEXPI-compliant JSON structures with the error:

Constraint AASd-127 violated: key 3 must be preceded by File or Blob @ /submodels/0/submodel_elements/1/value/2/value/17/value/3/first

However, the official DEXPI template (IDTA-02012-1-0_Template_DEXPI.json) uses exactly this structure with SubmodelElement before FragmentReference.

Root Cause

The constraint AASd-127 (from the general AAS metamodel) states that a FragmentReference must be preceded by a File or Blob key. However, in the DEXPI specification context, a SubmodelElement with value="ModelFile" is used as an exception to navigate to the ModelFile element before applying the fragment reference.

Expected Behavior

The validator should accept the following valid DEXPI RelationshipElement key structure (as shown in the official template):

{
  "idShort": "RelationshipElement_example",
  "modelType": "RelationshipElement",
  "first": {
    "type": "ModelReference",
    "keys": [
      { "type": "Submodel", "value": "urn:uuid:9f236679-e52d-4a52-aa85-dea871a89f9b" },
      { "type": "SubmodelElementCollection", "value": "Model01" },
      { "type": "SubmodelElement", "value": "ModelFile" },
      { "type": "FragmentReference", "value": "ProteusXML@ID=ProcessInstrumentationFunction-3" }
    ]
  },
  "second": {
    "type": "ExternalReference",
    "keys": [
      { "type": "GlobalReference", "value": "https://example.org/role/ProcessInstrumentationFunction-3" }
    ]
  }
}

Actual Behavior

The validator rejects the above JSON with Constraint AASd-127 violated: key 3 must be preceded by File or Blob.

Reproduction Steps

1. Generate or load a DEXPI-compliant AAS JSON with RelationshipElements in TagMapping/SubTagMapping (as per IDTA-02012-1-0)
2. Validate the JSON
3. Observe the constraint violation, even though the structure matches the official DEXPI template

Evidence

• DEXPI Specification: IDTA-02012-1-0 (Tables 6 & 7, pages 20-21)
• Official DEXPI Template: IDTA-02012-1-0_Template_DEXPI.json (included in IDTA-02012-1-0 i.e. the github repo of idta aas)
• Example from template (line excerpt):

  "keys": [
    { "type": "Submodel", "value": "https://epc.org/smid/9f236679-e52d-4a52-aa85-dea871a89f9b" },
    { "type": "SubmodelElementCollection", "value": "Model01" },
    { "type": "SubmodelElement", "value": "ModelFile" },
    { "type": "FragmentReference", "value": "ProteusXML@ID=ProcessInstrumentationFunction-3" }
  ]
  

Suggested Fix

The AASd-127 constraint should be refined to allow SubmodelElement (with value="ModelFile") as a valid predecessor to FragmentReference in the context of DEXPI RelationshipElements, or a DEXPI-specific constraint exception should be added.

Environment

• Validator Version: 1.0.3
• DEXPI Specification Version: IDTA-02012-1-0 (2023-09-01)

[aditya-work-dev]

Thank you for your query. This forum is intended for questions and issues related to the AAS Test Engine. Since the issue you reported concerns the AAS Specifications, I recommend forwarding your request to the AAS Specifications team.

[kommerzienrat]

No, the test engine does not comply with the specification when it comed to the DEXPI AAS submodel. That is what needs to be fixed. It throws an error when it must not.

[kommerzienrat]

Since this issue is caused by erroneous code, I fixed it in my pull request from last year: #102