TADESSE TAREKE.pdf - Addis Ababa University

Background Business Rules Object-Oriented Method
Figure 3 below depicts the relationships between these levels or layers with the
corresponding examples.
Figure 3: OMG UML 4-Layer Architecture [60]
An instance at a certain level is always an instance of something defined at one
level higher. An actual runtime object at M0 is an instance of a class defined at M1.
The classes defined in UML models at M1 are instances of the concept Class
defined at M2. The UML metamodel itself is an instance of M3. Other meta-models
that define other modeling languages are also instances of M3. Common data
Warehouse Model (CWM) is one example.
2.4 DESIGN PATTERNS AND FRAMEWORKS
2.4.1 ABOUT DESIGN PATTERNS AND FRAMEWORKS
Design patterns are a form of best-practices documentation and not a language
feature or idioms [18, 19]. Their intent is to communicate the observations,
analysis, and recommendations of experienced developers with others in an
effective way [18]. The authors of [18] are sometimes referred to Gang Of Four
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