Metamodel Extension

This chapter describes metamodel for diagram information which diagram interchange mechanism relies on. It is an extension of UML metamodel and is currently based on UML 1.4. existing mechanism of XMI[UML] for exchanging models includes only model information but not graphical information. diagram interchange extension allows graphical information to be included for diagrams used in UML models.

This extension adds a new package to current UML metamodel packages. Yet existing standard is not changed in any way. Also, changes to UML metamodel due to version updates should not affect this model as long as high-level notions of Core::Element (as used in UML 1.x) and Elements::Element (as used in UML 2.0 as well as all metamodels based on Common Core) are maintained. extension and UML metamodel are kept largely independent such that solely links from extension to UML metamodel are included. Thus, graphical and model information are cleanly separated.

In addition, conflicts with tools supporting current standard are avoided and full backward compatibility is maintained. Flexibility for future extensions to UML itself is provided.

The proposed package contains elements to reflect the diagram information of any diagram element of the standard UML. Tool-specific extensions can be defined in additional packages. For example, if a tool adds drawing capabilities for additional shapes, then an additional package to describe these can be provided. The purpose of this is to guarantee that tools not supporting these additional extensions are nonetheless able to generate a graphical representation by simply ignoring the information from an extra package. Figure 3 depicts the proposed metamodel for representation of diagram information.