Database Development Cycle

Transcription

1 Database Development Cycle Connolly/Begg Chapter 9 Overview Application Development Life Cycle Relationship to Databases Database Design Three levels Data Models Entity-Relationship Model Relational Model (c) Stephen Mc Kearney,

2 Information Systems The resources that enable the collection, management, control and dissemination of information throughout an organisation Connolly/Begg Database is a core component Therefore, database development must meet the organisation s objectives (c) Stephen Mc Kearney, Application Development Life Cycle System Definition Requirements Design Implementation Testing Maintenance (c) Stephen Mc Kearney,

3 Application Development Life Cycle System Definition Data planning; scope; boundaries Requirements User views Design Database Design Implementation Database building; data loading; data conversion Testing Database Testing Maintenance Database administration (c) Stephen Mc Kearney, Overview Application Development Life Cycle Relationship to Databases Database Design Three levels Data Models Entity-Relationship Model Relational Model (c) Stephen Mc Kearney,

4 Database Design (c) Stephen Mc Kearney, Database Design Design The process of constructing a model of all information used in an enterprise, independent of all physical considerations. Connolly/Begg High level data model Focuses on user requirements eg Entity-Relationship Model Independent of Implementation No hardware platform No DBMS No programming (c) Stephen Mc Kearney,

5 Aside: Selecting a DBMS Model Not buying Access, SQL Server, Oracle Main models Relational Object Network XML (Semi-Structured?) Each has different logical model Selecting a DBMS package Commercial decision No impact on conceptual design Limited impact on logical design Major impact on physical design (c) Stephen Mc Kearney, Database Design Design The process of constructing a model... based on a specific data model, but independent of a particular DBMS and other physical considerations. Connolly/Begg Target DBMS s data model Focuses on mapping conceptual model to DBMS model eg Relational Model Independent of Many Implementation Features No hardware platform, storage, indexes (c) Stephen Mc Kearney,

6 Database Design Design The process of producing a description of the implementation of the database on secondary storage Connolly/Begg Target DBMS & Hardware Focuses on mapping logical model to the DBMS eg base tables, file structures, indexes Dependent on Many Implementation Features Compromises made for efficiency and performance (c) Stephen Mc Kearney, Overview Application Development Life Cycle Relationship to Databases Database Design Three levels Data Models Entity-Relationship Model Relational Model (c) Stephen Mc Kearney,

7 Design Output - Data Model Model High level description of entities and relationships Specific description of data consistent with DBMS model Low level description of how to build database (c) Stephen Mc Kearney, Modelling Techniques Entity-Relationship Model Relational Data Model DBMS Specific Model (if any) (c) Stephen Mc Kearney,

8 Good Data Models (Connolly/Beggs) Structural validity Consistent with organisation Simplicity Ease of use Expressibility Distinguishes between types of data Nonredundancy No extraneous information Shareability Not application specific Extensibility Can evolve Integrity Consistent with organisation rules Diagrammatic Representation Easily represented by diagram (c) Stephen Mc Kearney, Database Design - Example Data Files, Index (c) Stephen Mc Kearney,