CHAPTER 3 Entity Relationship Modelling

CHAPTER 3 Entity Relationship Modelling

1. 3.0 Structural Constraint

   • 2 types
     • Cardinality Constraint
       • determine the number of possible relationships for each ratio
         • 1:1
         • 1:M
         • M:M
     • Participation Constraint
       • the existence of an entity depends upon its related to another entity through the relationship
       • 2 types
         • Total (mandatory)
           • wajib ada data (1,M)
         • Partial (optional)
           • boleh ada data & tak ada data pun tak apa (0,n)

2. 4.0 Problems E-R Model

   • 2 types
     • Fan Traps
       • relationship tu ada, tetapi tak clear so kita nk tukar kedudukan dia
       • solution tu connection yg dah sedia ada antara 2 entity
     • Chasm Traps
       • 2 entity asalnya tk ada relationship, tpi kita wujudkan relationship utk selesaikan masalah

3. 5.0 Enhanced Entity-Relationship (EE-R) Model

   • Superclass
     • entity type that include distinct subclasses required to be presented in a data model
   • Subclass
     • entity type that has distinct role and is also member of superclass
   • Specialization
     • kita wujudkan perbezaan anatara subclass 1 & 2. apakah ciri ciri yg membezakan dia
   • Generalization
     • kita focus attribute kpd subclasses utk membezakan dia