Query/View/Transformation Operational Mapping Language - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 572

The type returned from a resolve operation matches that provided, or a col-
lection (Sequence) of the type. If no type is specified, OclAny is the result type.
Technically, the specification calls for a return type of Object , but the current
QVTO implementation returns its subclass OclAny .

TIP
The conditional version of resolve can result in a performance advantage
over filtering the results because it avoids intermediate collection creation.

Let's consider our mindmap-to-requirements transformation to describe the
resolve functions. As you might recall, a mindmap has a collection of Relation-
ship elements that are mapped to Requirement dependency references when the
type of Relationship is of Type::DEPENDENCY . To create this mapping, we first
need to obtain the Requirement object that was created from the source Topic
in the Relationship. For this, we can use the following sourceReq variable
assignment:

mapping mindmap::Relationship::toDependency()
when { self .type = mindmap::Type::DEPENDENCY }

{

init {
var sourceReq : requirements::Requirement :=
self .source. resolve (requirements::Requirement)-> any ( true );

}
...
}

This mapping is invoked from the end block of our main mapping, so all
Topic to Requirement mappings are completed. In this case, the resolve oper-
ation returns all Requirement objects that were created from the Topic object ref-
erenced in our source reference. We know that there is a one-to-one mapping
in this case, so we can filter the resulting Sequence using any(true) .
Having obtained the Requirement mapped from the source Topic in our
Relationship, we now need to find the Requirement object created from the
Topic referenced by the target reference and add it to our collection of
sourceReq dependencies. We can accomplish this using another resolve oper-
ation. Although resolve returns all possible mappings, we know that only one
will be possible.

sourceReq.dependencies +=

self .target. resolve (requirements::Requirement);