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