UML Weekend Crash Course™ - To Parent Directory

Session 30—UML Modeling Tools 311
provide integration with a tool like Program Version Control Software (PVCS), StarTeam from
Starbase, ClearCase/ClearQuest from Rational, Visual SourceSafe from Microsoft, and others.
The remaining vendors save their projects as an encyclopedia or directory of some sort that
is easily identified and managed by any third-party version control package.
Version control is also especially valuable with object-oriented modeling. The diagrams
are used throughout the development process. The same diagram initially created in the
early phases is continuously changed through analysis and design and finally through
implementation. Without version control, you lose the history of the diagrams that explains
how you arrived at the current image.
Extended features
The rest of the features listed don’t appear in all tools; however, they are very valuable.
These features and how well they are implemented can set a tool apart from the rest. They
can also add substantially to the cost.
Round-trip engineering
Round-trip engineering is a hotly debated subject. It sounds great but can be challenging
to accomplish. The concept involves four types of translation between models and code.
Figure 30-2 provides a visual explanation to reference while you read through the following
definitions:
Forward engineering: A Class diagram is used to generate code that never existed
before.
Reverse engineering: Code is used to create a Class diagram that never existed before.
Maintenance involves work in both directions:
Diagram updates the code: The diagram changes so you need to regenerate the code.
Some tools replace the existing code, while others are smart enough to isolate the
changes and even comment out the replaced or deleted code.
Code updates the diagram: The code has changed so you need to update the diagram
to keep in sync. This is not as easy as it sounds. Always do it in very small increments.
Also, some diagram concepts, like aggregation and composition, are not
reflected in code. So you will need to modify the diagram to make certain that it
continues to represent your model accurately.
The maintenance phase is one of the reasons that vendors introduced markers. The markers
can represent modeling concepts that do not have code equivalents. Using this technique,
they can preserve the non-code constructs when the code is converted back into a
diagram during reverse engineering and code-to-diagrams updates.
Data modeling integration
Nearly every application requires a database. Most databases nowadays are relational. The
better tools have taken measures to incorporate data modeling options into their product.
Others have partnered with data modeling or database management vendors to provide the
linkage between a Class diagram and a data model.