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Collection of similar entities or concepts into a higher level concept. EMPLOYEE class collects all employees into one class A class has properties called “class properties”. EMPLOYEE class has class properties - e.g., average salary, total number of employees. Each member has values for own properties (e.g. name, address, salary): called member properties. | Enhanced Entity-Relationship and UML Modeling THE BASICS Fundamental Principle of Modeling: Data Abstraction Basic Process of Modeling Define building blocks for holding groups of data Use rules of a data model to establish relationships among blocks Add constraints - structural/ semantic Part 1: Fundamentals of Data Modeling 1 Inputs to Data Modeling 2 The Process of Modeling 3 Data Modeling Abstractions 4 Classification 5 Aggregation 6 Identification 7 Generalization 8 Coverage Constraints in Generalization 9 Cardinality and Participation Constraints Inputs to Data Modeling Using the products of requirements analysis Verbal and written communication among users and designers Knowledge of meaning of data Existing Programs Existing Files Existing Documents Existing Reports Application Planning / Documentation and Design Overall Process of Modeling Abstraction Use of some modeling discipline (Data Model) Use of a representation technique Language Diagramming Tools Analysis of . | Enhanced Entity-Relationship and UML Modeling THE BASICS Fundamental Principle of Modeling: Data Abstraction Basic Process of Modeling Define building blocks for holding groups of data Use rules of a data model to establish relationships among blocks Add constraints - structural/ semantic Part 1: Fundamentals of Data Modeling 1 Inputs to Data Modeling 2 The Process of Modeling 3 Data Modeling Abstractions 4 Classification 5 Aggregation 6 Identification 7 Generalization 8 Coverage Constraints in Generalization 9 Cardinality and Participation Constraints Inputs to Data Modeling Using the products of requirements analysis Verbal and written communication among users and designers Knowledge of meaning of data Existing Programs Existing Files Existing Documents Existing Reports Application Planning / Documentation and Design Overall Process of Modeling Abstraction Use of some modeling discipline (Data Model) Use of a representation technique Language Diagramming Tools Analysis of business rules/semantic constraints (these are typically beyond the capability of the data model) Types of Abstractions Classification A is a member of class B Aggregation B,C,D are aggregated into A A is made of/composed of B,C,D Generalization B,C,D can be generalized into A, B is-an A, C is- an A, D is-an A Specialization A can be specialized into B,C,D B,C,D are special cases of A Classification Abstraction Relationship between a class and its members John Smith, Sheela Patel, and Peter Wang are all employees. They are all members of a class: EMPLOYEE class EMPLOYEE John Smith Peter Wang Sheela Patel Each individual employee is a member of the class EMPLOYEE Classification Abstraction (contd.) MONTH January December February January, February etc. are members of the class “MONTH” Represents “member-of” relationship In object-oriented modeling : MONTH : an Object type or class January December : objects that belong to class MONTH Exhaustive enumeration of members: Classification - Class
