TY - UNPB
T1 - Derived classes as a basis for views in UML/OCL data models
AU - Balsters, H.
N1 - Relation: http://som.rug.nl/
date_submitted:2002
Rights: Graduate School/Research Institute, Systems, Organisations and Management (SOM)
PY - 2002
Y1 - 2002
N2 - UML is the de facto standard language for analysis and design in object-oriented frameworks.
Information systems, and in particular information systems based on databases and their applications,
rely heavily on sound principles of analysis and design. Many present-day database applications
employ object-oriented principles in the phases of analysis and design due to the advantages of
expressiveness and clarity of such languages as UML. Database specifications often involve
specifications of constraints, and the Object Constraint Language (OCL) - as part of UML - can aid in
the unambiguous modelling of database constraints. One of the central notions in database modelling
and in constraint specifications is the notion of a database view. A database view closely corresponds
to the notion of derived class in UML. This paper will show how the notion of a derived class in UML
can be given a precise semantics in terms of OCL. We will then demonstrate that the notion of a
relational database view can be correctly expressed as a derived class in UML/OCL. A central part of
our investigation concerns the generality of our manner of representing relational views in OCL. An
important problem that we address in this respect is the representation of product spaces and relational
joins. Joins are often essential in view definitions, and we shall demonstrate how we can express
Cartesian products and joins within the current framework of UML/OCL language by employing the
notions of derived class. As a consequence, OCL will be shown to be equipped with the full expressive
power of the relational algebra, offering support for the claim that OCL can be useful as a general
query language within the framework of the UML/OCL data model.
AB - UML is the de facto standard language for analysis and design in object-oriented frameworks.
Information systems, and in particular information systems based on databases and their applications,
rely heavily on sound principles of analysis and design. Many present-day database applications
employ object-oriented principles in the phases of analysis and design due to the advantages of
expressiveness and clarity of such languages as UML. Database specifications often involve
specifications of constraints, and the Object Constraint Language (OCL) - as part of UML - can aid in
the unambiguous modelling of database constraints. One of the central notions in database modelling
and in constraint specifications is the notion of a database view. A database view closely corresponds
to the notion of derived class in UML. This paper will show how the notion of a derived class in UML
can be given a precise semantics in terms of OCL. We will then demonstrate that the notion of a
relational database view can be correctly expressed as a derived class in UML/OCL. A central part of
our investigation concerns the generality of our manner of representing relational views in OCL. An
important problem that we address in this respect is the representation of product spaces and relational
joins. Joins are often essential in view definitions, and we shall demonstrate how we can express
Cartesian products and joins within the current framework of UML/OCL language by employing the
notions of derived class. As a consequence, OCL will be shown to be equipped with the full expressive
power of the relational algebra, offering support for the claim that OCL can be useful as a general
query language within the framework of the UML/OCL data model.
M3 - Working paper
BT - Derived classes as a basis for views in UML/OCL data models
PB - s.n.
ER -