@InProceedings{Kleppe:1998:IFOCLAUM,
  author =       "Anneke Kleppe and Jos Warmer and Steve Cook",
  title =        "Informal Formality? The {Object Constraint Language} and
                  its Application in the {UML} Metamodel",
  pages =        "127--136",
  abstract =     "Within the field of object technology it is being
                  recognised that constraints are a good means to produce
                  more precise and formal specifications. One proof of this
                  is that UML incorporates a standard constraint language
                  called OCL (Object Constraint Language). The availability
                  of OCL to every user of UML will undoubtedly encourage
                  many people to add constraints to their UML models. This
                  paper explains this language and shows the wide
                  applicability of OCL, e.g. to express invariants, pre-
                  and post- conditions, and guards. Probably the largest
                  application of OCL to date was its use to define the
                  metamodel of UML, and the experiences gained in this
                  application of OCL will be discussed.",
  booktitle =    "The Unified Modeling Language, UML'98 - Beyond the
                  Notation. First International Workshop, Mulhouse, France,
                  June 1998",
  editor =       "Jean B{\'e}zivin and Pierre-Alain Muller",
  year =         "1998",
}