Operations may be externally visible (public), visible to children (protected) or hidden (private). Adherence to this principal results in more maintainable code.īehaviour is captured in the class model using the operations that are defined for the class. Access to these data elements should be through the class's exposed behaviour or interface. A class has internal data elements that it is responsible for. The principal of data hiding or encapsulation is based on localisation of effect. When we work with dynamic diagrams, such as sequence diagrams and collaborations, we work with objects or instances of classes and their inter-actions at run-time. When we develop a logical model such as a structural hierarchy in UML we explicitly deal with classes. A class is a template or model from which instances or objects are created at run time. It defines both the data and the behaviour of a structural unit. The class is the basic logical entity in the UML. The techniques for discovering and elaborating that model are outside the scope of this article, so we will assume the existence of a well designed class model that requires mapping onto a relational database. It captures the both the data requirements and the behaviour of objects within the model domain.
Adding base class in visual paradigm uml software#
The Class Model in the UML is the main artifact produced to represent the logical structure of a software system. Some familiarity with object-oriented design, UML and relational database modelling is assumed. We will conclude with a review of the UML Data Profile (as proposed by Rational Software). We will then look at the techniques and issues involved in mapping from the class model to the database model, including object persistence, object behaviour, relationships between objects and object identity. We will begin with a quick tour of the two design domains we are trying to bridge: firstly the object-oriented class model as represented in the UML, and secondly the relational database model.įor each domain we look only at the main features that will affect our task. This is not to imply this is the only, best or simplest solution, but pragmatically it is one of the most common, and one that has the potential for the most misuse. This article is about only one of those choices, that is the layering of an object-oriented class model on top of a purely relational database. From the vendor aspect Oracle, IBM, Microsoft, POET and others offer similar but often-incompatible solutions. From the technological perspective, the choice is usually between pure Object-Oriented, Object-Relational hybrids, pure Relational and custom solutions based on open or proprietary file formats (eg. When it comes to providing reliable, flexible and efficient object persistence for software systems, today's designers and architects are faced with many choices.