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CONCEPTUAL SCHEMA DESIGN PROCESS

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  1. CONCEPTUAL SCHEMA DESIGN PROCESS Yr 12 IPT Information Processing and Technology, 2001

  2. Last Lesson • The UoD is the domain of relevant information. • An information system is designed through the Conceptual Schema Design Process (CSDP). • The first process of the CSDP is to state elementary facts. • EF are simple, unambiguous, irreducible and do not contain and, if, or, not, all, some, most. • EF contain entities, roles, reference modes and values. • The number of entities in an EF describes its arity. .

  3. Reference Scheme Student (first name)Mary studies / is studied by Subject (name)IPT Entities = Student, Subject Ref Modes = first name, name Role = studies / is studied by Values = Mary, IPT

  4. Arity • The arity of an elementary sentence is the number of entities that associate or play roles MaryJogs - unary Mary studies English - binary Mary received a B for English - ternary

  5. Design Cycle 1. State Elementary Facts Draw Conceptual Schema Diagram 2. 3. 4. 5. 6.

  6. Step 2. Draw Conceptual Schema Diagram • The Conceptual Schema Diagrams are a graphical representation of the elementary facts obtained from the first step. • Entity types are represented by ellipses: • Roles are represented by rectangles:

  7. Data and EF’s ... Elementary Facts: 2. Person (name) Gary lives in / is lived in by Suburb (suburb) Glenvale. 1. Person (name) Gary has / refers to Phone (Phone) 4636 7357.

  8. … and a CS Diagram Phone (Phone) Person (name) has 1. Person (name) Gary has / refers to Phone (Phone) 4636 7357. lives in 2. Person (name) Gary lives in / is lived in by Suburb (suburb) Glenvale. Suburb (suburb)

  9. Ternary Relationship 1. Student (Student) Megan studies Subject (Subject) IPT gained Result (Grade) HA

  10. Ternary Relationships • A ternary relationship is needed when two binary relationships do not convey the information required • Ternary relationships are drawn by nesting.

  11. A Ternary Relationship Subject (subject) Student (student) studies 1. Student (student) Megan studies Subject (subject) IPT gained Result (grade) HA gained Result (grade)

  12. Ternary or Binary?

  13. Summary • Drawing the CS Diagrams is the second step of the CS Design Process. • CS Diagrams are a graphical representation of elementary facts. • Ternary relationships require nesting. Entity (ref mode) Entity (ref mode) plays role

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