Multi-Level document structure requires a base-class for sub-sub-documents

[Tra5is]

Describe the bug
To create a document structure that has more than two levels of document references (Doc -> subDoc -> subDoc... etc) the odd-numbered levels are required to have a base-class. Otherwise the error ascribed_type_not_subsumed is returned when submitting new documents.

The issue appears to occur every other sub-document level. Effectively the even leveled sub-documents. So, levels 3 (SubDoc2), 5 (SubDoc4), etc require a base-class.

Part of this bug is that the error is not well documented and that the meaning of 'subsumed' is not clear in this context.

To Reproduce
Using the schema:

[
    {
        "@base": "terminusdb:///data/",
        "@schema": "terminusdb:///schema#",
        "@type": "@context"
    },
    {
        "@base": "SubDoc2/",
        "@id": "SubDoc2",
        "@key": {
            "@type": "ValueHash"
        },
        "@subdocument": [],
        "@type": "Class",
        "Sub2Prop": "xsd:string"
    },
    {
        "@base": "Top/",
        "@id": "TopLevelDoc",
        "@key": {
            "@type": "Random"
        },
        "@type": "Class",
        "Prop1": "xsd:string",
        "SubDoc": {
            "@class": "SubDoc1",
            "@type": "Optional"
        }
    },
    {
        "@base": "SubDoc1/",
        "@id": "SubDoc1",
        "@key": {
            "@type": "Random"
        },
        "@subdocument": [],
        "@type": "Class",
        "Sub1Prop": "xsd:string",
        "SubSubDoc": {
            "@class": "SubDoc2",
            "@type": "Optional"
        }
    }
]

To represent a multi-level document:

{
	"Prop1": "Top",
	"SubDoc": {
	  "Sub1Prop": "Sub",
	  "SubSubDoc": {
	    "Sub2Prop": "SubSub"
	  }
	}
}

and creating the document with a rest POST call (from powershell):

$body = @"
{
	"Prop1": "Top",
	"SubDoc": 
	{
	  "Sub1Prop": "Sub",
	  "SubSubDoc": {
	    "@type": "terminusdb:///schema#SubDoc2",
	    "Sub2Prop": "SubSub"
	  }
	}
}
"@

$user = ""
$pass = ""
$pair = "$($user):$($pass)"
$encodedCreds = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes($pair))
$basicAuthValue = "Basic $encodedCreds"
$Headers = @{
    Authorization = $basicAuthValue
    'Content-Type' = 'application/json'
}

Invoke-WebRequest `
	-Uri "http://<your terminus db host>/api/document/admin/test3/local/branch/main?message=Test&author=Test&graph_type=instance&full_replace=false&raw_json=false" `
	-Method POST `
	-Body $body `
	-Headers $headers

Results in the error:

"reason": {
              "terminusdb:///schema#SubSubDoc": {
                "@type": "ascribed_type_not_subsumed",
                "ascribed_type": "terminusdb:///schema#SubDoc2",
                "document": {
                  "@type": "terminusdb:///schema#SubDoc2",
                  "Sub2Prop": "SubSub"
                },
                "required_type": "terminusdb:///schema#SubDoc2"
              }
            }

The error can be avoided by adding a base-class to SubDoc2 and referencing that from SubDoc1.

[
    {
        "@base": "terminusdb:///data/",
        "@schema": "terminusdb:///schema#",
        "@type": "@context"
    },
    {
        "@base": "SubDoc2/",
        "@id": "SubDoc2",
        "@inherits": "SubDocBase2",
        "@key": {
            "@type": "ValueHash"
        },
        "@subdocument": [],
        "@type": "Class",
        "Sub2Prop": "xsd:string"
    },
    {
        "@base": "Top/",
        "@id": "TopLevelDoc",
        "@key": {
            "@type": "Random"
        },
        "@type": "Class",
        "Prop1": "xsd:string",
        "SubDoc": {
            "@class": "SubDoc1",
            "@type": "Optional"
        }
    },
    {
        "@abstract": [],
        "@base": "SubDocBase2/",
        "@id": "SubDocBase2",
        "@key": {
            "@type": "Random"
        },
        "@subdocument": [],
        "@type": "Class"
    },
    {
        "@base": "SubDoc1/",
        "@id": "SubDoc1",
        "@key": {
            "@type": "Random"
        },
        "@subdocument": [],
        "@type": "Class",
        "Sub1Prop": "xsd:string",
        "SubSubDoc": {
            "@class": "SubDocBase2",
            "@type": "Optional"
        }
    }
]

Expected behavior

The extra base class should not be required.

Screenshots

Info (please complete the following information):

• OS: Ubuntu 22.04.3 LTS
• Installed via snap (version 11.1.9), run via terminusdb serve