QVT — 7.13.1 Collection conversions

Given a property template in which the property is a collection, under what
circumstances:

Is it permissible for the right hand side to be a non-collection?

Is it permissible for the right hand side to be a different collection kind.

Add the following to the description of class PropertyTemplateItem in section 7.11.2.4:

A property template item has a valid match when the value of the referred property matches the value specified by the value expression. The following rules apply when the value is specified by a template expression:

• If the value expression is an object template expression and the referred property is single-valued then the property value must match the object template expression.
• If the value expression is an object template expression and the referred property is multi-valued then at least one of the property values must match the object template expression.
• If the value expression is a collection template expression and the referred property is single-valued then the property value is treated as a singleton collection that must match the collection template expression
• If the value expression is a collection template expression and the referred property is multi-valued then the collection of property values must match the collection template expression. The following rules apply:
  o If the property value is a set, then the collection type of the collection template expression must be a set.
  o If the property value is an ordered set, then the collection type of the collection template expression can be one of set, sequence or ordered set.
  o If the property value is a sequence, then the collection type of the collection template expression can be one of set, sequence or ordered set. When the collection type is a set or an ordered set, a valid match requires that each value of the property be unique.