Expressing Model Constraints Visually With VMQL
OCL is the de facto standard language for expressing constraints and queries on UML models. However, OCL expressions are very difficult to create, understand, and maintain, even with the sophisticated tool support now available. In this paper, the authors propose to use the Visual Model Query Language (VMQL) for specifying constraints on UML models. They examine VMQL's usability by controlled experiments and its expressiveness by a representative sample. They conclude that VMQL is less expressive than OCL, although expressive enough for most of the constraints in the sample. In terms of usability, however, VMQL is superior to OCL, although the experimental evidence they present here is not as compelling as the one they presented when comparing VMQL and OCL on model querying.