Presentation on theme: "1 CONCEPTUAL SCHEMA DESIGN PROCESS Information Processing and Technology, 2001 Yr 12 IPT."— Presentation transcript:
1 CONCEPTUAL SCHEMA DESIGN PROCESS Information Processing and Technology, 2001 Yr 12 IPT
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..
Student (first name) Mary studies / is studied by Subject (name) IPT Reference Scheme Values = Mary, IPT Entities = Student, Subject Ref Modes = first name, name Role = studies / is studied by
Arity §The arity of an elementary sentence is the number of entities that associate or play roles Mary Jogs - unary Mary studies English - binary Mary received a B for English - ternary
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:
Data and EF’s Person (name) Gary has / refers to Phone (Phone) Person (name) Gary lives in / is lived in by Suburb (suburb) Glenvale. Elementary Facts:
… and a CS Diagram Person (name) Phone (Phone) Suburb (suburb) lives in has 1. Person (name) Gary has / refers to Phone (Phone) Person (name) Gary lives in / is lived in by Suburb (suburb) Glenvale.
Ternary Relationship 1. Student (Student) Megan studies Subject (Subject) IPT gained Result (Grade) HA
Ternary Relationships §A ternary relationship is needed when two binary relationships do not convey the information required §Ternary relationships are drawn by nesting.
A Ternary Relationship Student (student) Result (grade) Subject (subject) studies gained 1. Student (student) Megan studies Subject (subject) IPT gained Result (grade) HA
Ternary or Binary?
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