Type casting is used to refine the results of a query.
A type is not assigned to schema elements that can have more than
one valid type. You define the types for these elements with the cast to type feature in the schema view bar.
About this task
Type casting works essentially as an alternate filter for
data source elements. A cast query filters the results of the regular
query to return only the elements that can be cast to the selected
type. After the type is selected, it becomes available in the Schema
view under the
anyType element. Queries built using
cast allow access to all the child elements and attributes of the
type cast. The result set returned by a cast query is identical to
the result set returned by a query that is filtered with an equivalent
IsKindOf predicate. The difference between the cast query and filtered
query is that a cast query gives access to the cast type attributes
and child elements while the filtered query does not.
Note: At present,
the data sources that support type casting are, IBM® Rational® Tau and IBM Rational Rhapsody®.