slot_derivations at top-level of TransformationSpecification has no effect in SchemaMapper

[pkalita-lbl]

According to the TransformationSpecification model, a slot_derivations list is allowed at the top level. The model says that it specifies "instructions on how to derive a set of top level slots in the target schema".

Based on that, I would expect that with this source schema:

# source schema
name: test_source
id: http://example.com/test_source

slots:
  a_slot:
    description: This is a top-level slot definition
    range: string

classes:
  AClass:
    description: This is a top-level class definition
    slots:
     - a_slot

And this transformation spec:

# transformation spec
title: Transform test_source into test_target
source_schema: test_source
target_schema: test_target

slot_derivations:
  a_slot:
    derived_from: a_slot
    overrides:
      description: TOP-LEVEL DERIVED SLOT DEFINITION

class_derivations:
  AClass:
    populated_from: AClass
    slot_derivations:
      a_slot:

I think I would have expected that the top-level derivation of a_slot would have had an effect before the derivation of a_slot within the context of the AClass class derivation. In other words, I was expecting to get something like this as a result:

# expected target schema
name: test_source-derived
id: http://example.com/test_source-derived
default_prefix: http://example.com/test_source-derived/
classes:
  AClass:
    name: AClass
    description: This is a top-level class definition
    attributes:
      a_slot:
        name: a_slot
        description: TOP-LEVEL DERIVED SLOT DEFINITION
        alias: a_slot
        domain_of:
        - AClass
        range: string

Instead I just get the a_slot description from the source top-level slot definition in the target schema:

# actual target schema
name: test_source-derived
id: http://example.com/test_source-derived
default_prefix: http://example.com/test_source-derived/
classes:
  AClass:
    name: AClass
    description: This is a top-level class definition
    attributes:
      a_slot:
        name: a_slot
        description: This is a top-level slot definition
        alias: a_slot
        domain_of:
        - AClass
        range: string