Abstract:


Using Patterns to Develop Consistent Design Constraints


Michael Wahler



Developing constraint specifications for class models is a 
time-consuming and error-pronetask because typical 
specifications contain numerous constraints, which in 
addition oftenstate complex facts about the elements of the 
model. As the size and the complexity of constraint specifications 
grow, so does the probability of inadvertently specifying 
inconsistent models that cannot be instantiated because of 
contradictory constraints.In this thesis, we introduce a novel 
approach to developing consistent constraint specifications based 
on constraint patterns. The input for this approach is an 
unconstrained class model and the output is a formal constraint 
specification. The approach comprisesfour phases. First, class 
models are automatically analyzed to elicit potentially missing 
constraints. Second, a library of composable constraint patterns 
allows developers to writeconcise constraint specifications based 
on the results from the elicitation phase. Third, thisapproach 
contains consistency assertions on the constraint pattern library 
that enable automaticconsistency analysis of pattern-based 
constraint specifications. As basis for theseconsistency observations, 
we provide formal definitions of consistency properties of 
constrained class models. Fourth, pattern-based constraint 
specifications are transformed intological expressions or code 
in a programming language.The focus of the approach is on 
effectiveness and practicability. Therefore, we introducea tool 
that allows model developers to follow the theoretic approach 
in a guidedway and effectively apply it in modeling projects. 
We use this tool to conduct severalcase studies in which we 
validate that our approach improves the state-of-the-art constraint 
development in terms of detecting missing constraints, shortening 
developmenttime, avoiding inconsistencies, and yielding more 
comprehensible constraints.