Abstract:
Since the early software models, constraints specification and semantics in conceptual models have proven
their importance in software engineering methodologies. At present, extensible Markup Language (XML),
with its rich set of constraints and semantics becoming the dominant standard for storing, describing and
interchanging data among various Enterprises Information Systems (EIS) and databases. In combination
with the increased reliance on semi-structured data schemas (such as XML, RDFS, OWL-S etc.), there
exists a requirement to model, design, and constrain semi-structured data and the associated semantics at a
higher level of abstraction than at the instance or data level. While the Object-Oriented (OO) conceptual
models offers the power in describing and modeling real-world data semantics, constraints and their interrelationships
in a form that is precise and comprehensible to users, they provide insufficient modeling
constructs for utilizing XML schema like data descriptions and constraints. Conversely, most semistructured
schema languages lack the ability to provide higher levels of abstraction (such as conceptual
models) that are easily understood by humans. To this end, it is interesting to investigate conceptual and
schema formalisms as a means of providing higher level semantics in the context of XML-related data
engineering. In this paper, we present a visual constraint model for providing explicit constraints for a
layered view model [1] for XML. First we briefly outline the view model and then provide a detailed
discussion on modeling issues related to view constraints specification using two OO modeling languages,
namely OMG's UML/OCL and XML Semantics nets (XSemantic nets). To demonstrate our concepts, we
also provide an illustrative case study example based on a real-world application domain.
