DB analyse og modellering Jesper Tørresø DAB1 F Februar 2008
Metoder! ”Top down” ”Buttom Up” Work A round (Up, Down, På ”kryds og tværs”) Iterationer. Den ”rigtige” metode medføre design af en normaliserbar database. –”Virkemåden for DDS-Lite er en metode”.
Proces
Metoder [TEOREY] har en formel omfattende liste af artefakter, som indgår i deres metode. [RUSSEL] giver principperne som er de mest kendetegnede for DB–analyse og – design. Jeg har nogle principnoter
[Teorey] metode 1 Overordnede trin –Entity Clustering (Gælder for store systemer med mange entiteter > (Ikke for DAB1) –Requirements analysis. What is the DB to be used for,what must it contain and how will i proces data (what comes out)? –Conceptual data modeling (The most important part from a technically view) Classifiy entities and attributes or classes and attributes. Identify generaliztion hierecahies (ERD and UML) Define relationships or associations and association classes –First all possible binary and unary degreed relationships –Review redundant relationships. –Then if needed ternary (or n-ary) relationships.
Metode: Conceptual Scope A Schema/Diagram is a data model that is intended to be used with a database system –External schemas are defined for the users of a database –Logical schema defines the representation as a collection of tables that are stored in a database server –Internal schema defines the representation used by the database server to store the tables in memory or files
[Teorey] metode 2 –View integration methods. Merging different ”types of abstraction” Goal in schema integration –to create a non-redundant unified (global) conceptual schema/diagram –completeness - all components must appear in the global schema/diagram –minimality - remove redundant concepts in the global schema/diagram –understandability - does global schema/diagram make sense?
[Teorey] metode 3
[Teorey] metode 4
[Teorey] metode 5