DES715 – Database Design Conceptual design

Database Life Cycle Database initial study Database design Implementation Testing Operation Maintenance

Conceptual requirements Accuracy Consistency Integrity Accessibility Shared resource

Data anomalies Data redundancy results in anomalies with Insertion Deletion modification

Accessibility To support a proper performance we must ensure: Structured information space Data units may be uniquely identified Characteristics of data units are described Relationships of data units determined and described

Shared resource Data management Transaction management DBMS as the tool of implementing database management

Staged design Conceptual Logical Physical

Conceptual data modeling Entity Attributes Relationships Presented as ERD

Logical data modeling Hierarchical Network Relational Flat file Object-oriented Data warehousing

Entity discovering Read functional description of the system Examine reports, user’s view, other available information Look for Nouns Examine their role in business activity – are they principal participants (Entities) or serves as descriptors (Attributes) Make initial assumption to determine entities and their attributes You may change it later after applying design technique

Attributes Atomic or Composite Derived Creates Multivalued dependency (MVD) Serves as Unique Identifier (PK) Has its Domain

Other useful information to collect Data value Originator User’s data input Calculated on the base of other attributes values Generated by the system

Entity relationships Association, 1:1, 1:M, M:N Strong/Weak entities Supertype/Subtype Recursive

Relationship characteristics Connectivity (multiplicity in UML) – 1:1, 1:M, M:N Optionality Cardinality

Relationships discovery Ask the right questions to identify Relationship type Connectivity type Optionality Cardinality Attributes of relationships Specify business rules Create ERD