Model-Driven Engineering - Model-Driven and Software Product Line Engineering - page 90

The oAW expression language. The oAW expression
language is a syntactical mixture of Java and OCL.
For instance, to access a model element property, the
following syntax is used: myModelElement.property .
Respectively, a boolean expression looks like this:
!("textExample".startsWith('t') && ! false) . The
expression language provides several literals for built-in
types, for example, the boolean literals are true and false .
Like OCL, the expression language also defines several
special operations on collections such as select , collect ,
reject , forAll and exist between others. For instance,
the forAll operation allows specifying a boolean expression,
which must be true for all objects in a collection in order for
the forAll operation to return true : collection.forAll
(v | boolean-expression-with-v) . The expression
language includes conditional expressions (if and switch
expressions), expressions to instantiate new objects (create
expressions) and expressions to define local variables
(let expressions) among others.
3.6.4. The Xtend language
The Xtend language is a textual and functional
transformation language. As said before, Xtend is built
on the common type system and expression language of oAW.
Listing 3.10 presents an example of an Xtend file including
transformation rules to transform models that conform
to the class metamodel from Figure 3.2 into models that
conform to a metamodel of relational database schemas for a
relational database management system. The metamodel of
the relational database schema has two metaconcepts, Table
and Column .A Table contains columns and both Table and
Column have a name property.
In line 1 and line 2 of Listing 3.10, import statements are
usedtoimportthenamespacesofseveraltypes;inthiscase,the
types corresponding to metaconcepts of the classMetamodel