Textual notations and UML compliance

One common misconception is that UML is a graphical language and that any tools adopting alternative notations (such as a textual one) are inherently non-compliant. That can’t be farther from the truth. Read on to understand.

The fact is that the UML specification clearly separates abstract syntax (the kinds of elements and how they relate) and semantics (what they mean) from concrete syntax (what they look like), and states that there are two types of compliance:

  • abstract syntax compliance
  • concrete syntax compliance

Concrete syntax compliance means that users can continue to use a notation they are familiar with across different tools. This is important when UML is used as a communication tool in a team environment. Architects, designers, programmers and even many business analysts speak the same language.

Abstract syntax compliance means that users can move models across different tools, even if they use different notations. This is essential when UML is used as a basis for model-driven development. You might want to use tool A for creating the model, tool B for validating the model, tool C for somehow transforming/enhancing the model and tool D for generating code from it (a common form of MDD tool chain).

The TextUML Toolkit uses a textual notation that strictly exposes the UML semantics, but it is not compliant with the language concrete syntax by any means. On the other hand, the toolkit uses Eclipse UML2′s XMI flavor for persisting models and thus is fully compliant regarding the abstract syntax. That is consistent with the vision for the product: a tool from developers for developers that want to build software in a more sane way: the model-driven way. Developers can create models using a notation they are more productive with. Models can then be used as input for code generation using many of the tools available in the market. If non-developers might frown upon a textual modeling notation, they will always have the option of using their favorite graphical-notation based tools for reading the models. I mean, if their tool of choice is abstract syntax compliant as well.

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