CONCEPTUAL SCHEMA DESIGN PROCESS Yr 12 IPT 1

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

Information Systems Database - a collection of (sorted) data Information Systems - is a database along with the means to effectively manipulate the information it contains e. g. libraries, video hire, employee records, student records, Microsoft Access. Information Processing and Technology 2001 2

Database Views § internal view - the way data is stored onto a system § external view - the user’s view § conceptual view - the way the data relates *The conceptual view is independent of the system the database is implemented on. Information Processing and Technology 2001 3

Universe of Discourse (Uo. D) • The Uo. D is the domain of information being discussed by the client and database designer. Information Processing and Technology 2001 4

Conceptual Schema Design Process • The conceptual view is created by the Conceptual Schema Design Process (CSDP) • NIAM (Nijssens Information Analysis Method) developed by GM Nijssen and ED Falkenberg l a process that links / structures information (Uo. D) by expressing facts and constraints graphically l also known as Object Role Modeling Information Processing and Technology 2001 5

What does this data mean? Information Processing and Technology 2001 6

Design Cycle 1. State elementary facts 2. 3. 4. 5. 6. Information Processing and Technology 2001 7

1. State Elementary Facts • This step involves expressing information relevant to the Uo. D as elementary facts (EF). • EF are simple unambiguous sentences that make statements about the Uo. D. • EF are irreducible. They cannot be broken down into smaller parts and still convey the same information. • EF do not use terms such as and, or, not, if, all, some or most. • At this stage, or before, examples of information relevant to the database should be collected. Information Processing and Technology 2001 8

1. State Elementary Facts The simplest type of elementary fact states that an object plays a role: Mary jogs This elementary fact states that an object (Mary) plays a role (jogs) Information Processing and Technology 2001 9

Which of these are elementary facts? § § § Leroy plays for the Bullets. Mary does not smoke. Ken and Jerry play hockey. Jenny likes chocolate and ice-cream. Jim flew to Sydney. Alana flew to Melbourne and then to Sydney. Mary ate Coco Pops for breakfast. Everybody loves somebody sometime. Rover begs. I can never see what is in those 3 d pictures. Barry eats all berries. Does Julie run? Information Processing and Technology 2001 10

Reference Scheme § Elementary sentences are composed of four key elements 1. objects/entities 2. reference mode 3. roles 4. value or labels § The use of a reference scheme avoids ambiguity. Information Processing and Technology 2001 11

Reference Scheme § Object / entity types - are common groups that play roles Mary Studies English Information Processing and Technology 2001 12

Reference Scheme Roles - a role is a part played by an entity Mary studies English Information Processing and Technology 2001 13

Reference Scheme § reference mode - the reference mode is a way of identifying an entity. Common reference modes are names, numbers, ID codes. They will be the fields in the database that you are creating. Student with first name Mary Information Processing and Technology 2001 14

Reference Scheme § Values - a value or label gives a specific example of the entity. ref. mode entity Student with the first name Mary role studies Value / Subject with the name IPT label ref. mode Information Processing and Technology 2001 15

Arity § The arity of an elementary sentence is the number of entities that associate or play roles Information Processing and Technology 2001 16

Arity - Unary Mary Jogs 1 entity Information Processing and Technology 2001 17

Arity - Binary Mary studies English 2 1 Information Processing and Technology 2001 18

Arity - Ternary Mary received a B for English 1 2 Information Processing and Technology 2001 3 19

Arity - Quaternary Mary has English in Lesson 1 on Monday 1 2 3 4 And so on… Information Processing and Technology 2001 20

Summary § The Uo. D 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, irreducible and do not contain and, if, or, not, all, some, most § EF contain entities, roles, reference modes and values / labels. § The number of entities in an EF describes its arity. . Information Processing and Technology 2001 21