INFS1603 Lecture Notes - Lecture 8: Object-Oriented Analysis And Design, Class Diagram, Subtyping

• School: UNSW, UNSW Sydney
• Department: Information Systems
• Course: INFS1603
• Professor: All

Document Summary

8. 1 benefits/limitations er/rbd design: object modelling the world according to similar objects (similar to entity focus what the object can do, rather storing attributes). Limitations of rdb design: er models cannot adequately support complex data, poor represe(cid:374)tatio(cid:374) of (cid:862)real-(cid:449)orld e(cid:374)tities(cid:863) leads to many joins during query processing; slow, semantic overloading. Complex data, complex system: limited types of operations supported, the handling of recursive queries is difficult, schema changes are difficult. Relatio(cid:374)al (cid:373)odelli(cid:374)g of data is (cid:374)ot the (cid:862)perfe(cid:272)t(cid:863) solutio(cid:374). Relational modelling is not the only approach to data modelling. 8. 2 oo modelling concepts (object, class, encapsulation, inheritance, aggregation, Objects and classes: object-oriented analysis and design (ooad) models the world in objects, an object is an entity that has a well-defined role in the application domain, has a state, behavior and identity. Class diagrams: class diagrams show the relationships between objects classes, there are two categories of relationships, associations: horizontal relation between two object classes.