Doing away with custom UML metaclasses in TextUML

The TextUML Toolkit has since release 1.2 had a metamodel extension package (inaptly named ‘meta’). This metamodel extension package defined new metaclasses not available in UML such as:

  • closure – an activity that has another activity as context
  • conversion action – an action that flows an input directly as output just changing the type
  • literal double – a literal value for double precision numeric values
  • signature – a classifier that contained parameters, the type of a closure
  • meta value specification – a value specification for meta references
  • collection literals – a value specification that aggregates other value specifications

Turns out extending the UML metamodel by definining new packages and metaclasses is a bad idea. Some reasons (yes, I am feeling ‘bullety’):

  • it is non-standard
  • other UML tools cannot read instances of your metaclasses, some won’t read your models at all if they have *any* unknown metaclasses
  • there is little documentation on how to maintain these kinds of metamodel extensions
  • since it is not the mainstream approach, we are bound to encounter more issues

Because of that, release 1.6 will rely exclusively on profiles and stereotypes for extending the UML metamodel.

What to expect

For conventional users of the Toolkit, this change might possibly go unnoticed, barring any potential bugs introduced in the process.

People using the built-in base package and the base_profile will be directly affected. The elements in these models are still provided, by they are now in the new mdd_extensions profile, or one of the new mdd_types, mdd_collections and mdd_console packages.

We apologize for any inconvenience these changes might bring, but we strongly believe they are required to make the TextUML Toolkit a better product. If you have any trouble moving to 1.6 (to be released later this month), make sure to hit the user forums or report issues.

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