Improvements in USE 2.2.0

This document briefly describes major changes of USE since the 2.0.1 release

• UML association classes are now supported
• Association end navigation can now be qualified to resolve ambiguous situations (regards higher order reflexive associations and reflexive association classes)
• The 'Generator' module has been integrated into USE
• Several minor changes have been made

Association classes can now be specified in the model description (.use file) Since an association class is both a class and an association, it can contain attributes and operations sections. The following example demonstrates how association classes can be specified in USE 2.2.0:

model AssociationClassModel class Company attributes name : String town : String end class Person attributes ssn : String age : Integer end associationclass WorksFor between Company[0..1] role employer Person[1..*] role employee attributes salary : Integer end associationclass EmployeeRanking between Person[*] role bosses Person[*] role employees attributes score : String end

A link object (an instance of an association class) can be created as follows:

use> !create IBM:Company use> !create Ada:Person use> !create AdaWorksForIBM:WorksFor between (IBM, Ada)

In certain cases the simple dot operator based navigation is ambiguous, because the source end to be used has to be chosen, too. This problem regards higher order reflexive associations and reflexive association classes. In the current USE version, the standard OCL qualification mechanism can be used to select a source association end. The following class and object diagrams demonstrate the problem:

The following navigation is ambiguous:

use> ? Ada.employeeRanking.score < input >:1:5: The navigation path is ambiguous. A qualification of the source association end is required.

By qualifying the navigation by selecting 'bosses' as the source association end (in square brackets), the expression evaluates as follows:

use> ? Ada.employeeRanking[bosses].score -> Bag{90} : Bag(Integer)

USE was extended by a tool called Generator for generating valid snapshots for given class models. The snapshots are generated by written procedures. Additional invariants can be added to verify correctness in the generated snapshot.

If you would like to learn more about the Generator please have a look into the following papers.

(back)