“DOK 322 DBMS” Y.T. Database Design Hacettepe University Department of Information Management DOK 322: Database Management Systems

“DOK 322 DBMS” Y.T. Last Time F File Management Systems vs. DBMSs F Advantages and Disadvatages of DBMS F Components of DBMS F MS Access 2000 (Lab)

“DOK 322 DBMS” Y.T. DBMS Benefits F Minimal Data Redundancy F Consistency of Data F Integration of Data F Sharing of Data F Ease of Application Development F Uniform Security, Privacy, and Integrity Controls F Data Accessibility and Responsiveness F Data Independence F Reduced Program Maintenance

“DOK 322 DBMS” Y.T. Database Environment CASE Tools DBMS User Interface Application Programs RepositoryDatabase

“DOK 322 DBMS” Y.T. Database Components DBMS =============== Design tools Table Creation Form Creation Query Creation Report Creation Procedural language compiler (4GL) ============= Run time Form processor Query processor Report Writer Language Run time User Interface Applications Application Programs Database Database contains: User’s Data Metadata Indexes Application Metadata Kroenke, Database Processing

“DOK 322 DBMS” Y.T. Terms and Concepts F Database: –A self-describing collection of integrated records (Kroenke). –A collection of similar records with relationships between the records. (Rowley) –A collection of stored operational data used by the application systems of some particular enterprise. (C.J. Date)

“DOK 322 DBMS” Y.T. Terms and Concepts F Enterprise –Organization F Entity –Person, Place, Thing, Event, Concept... F Attributes –Data elements (facts) about some entity –Also sometimes called fields or items or domains F Data values –instances of a particular attribute for a particular entity

“DOK 322 DBMS” Y.T. Terms and Concepts F Key –an attribute or set of attributes used to identify or locate records in a file F Primary Key –an attribute or set of attributes that uniquely identifies each record in a file

“DOK 322 DBMS” Y.T. Terms and Concepts F Models –(1) Levels or views of the Database u Conceptual, logical, physical –(2) DBMS types u Relational, Hierarchic, Network, Object- Oriented, Object-Relational

“DOK 322 DBMS” Y.T. Models (1) Conceptual Model Logical Model External Model Conceptual requirements Conceptual requirements Conceptual requirements Conceptual requirements Application 1 Application 2Application 3Application 4 Application 2 Application 3 Application 4 External Model External Model External Model Internal Model

“DOK 322 DBMS” Y.T. Database System Life Cycle Growth, Change, & Maintenance 6 Operations 5 Integration 4 Design 1 Conversion 3 Physical Creation 2

“DOK 322 DBMS” Y.T. Another View of the Life Cycle Operations 5 Conversion 3 Physical Creation 2 Growth, Change 6 Integration 4 Design 1

“DOK 322 DBMS” Y.T. Database Models F Models(2): DBMS types –Hierarchical –Network –Relational –Object-Oriented

“DOK 322 DBMS” Y.T. Database Data Models F Hierarchical Model –Similar to data structures in programming languages. Books (id, title) PublisherSubjects Authors (first, last)

“DOK 322 DBMS” Y.T. Database Data Models F Network Model –Provides for single entries of data and navigational “links” through chains of data. SubjectsBooks Authors Publishers

“DOK 322 DBMS” Y.T. Database Data Models F Relational Model –Provides a conceptually simple model for data as relations (typically considered “tables”) with all data visible.

“DOK 322 DBMS” Y.T. Database Data Models F Object Oriented Data Model –Encapsulates data and operations as “Objects” Books (id, title) PublisherSubjects Authors (first, last)

“DOK 322 DBMS” Y.T. Database Design Process Conceptual Model Logical Model External Model Conceptual requirements Conceptual requirements Conceptual requirements Conceptual requirements Application 1 Application 2Application 3Application 4 Application 2 Application 3 Application 4 External Model External Model External Model Internal Model

“DOK 322 DBMS” Y.T. Database Design Process F Conceptual Requirements –Systems Analysis Process u Examine all of the information sources used in existing applications u Identify the characteristics of each data element –numeric –text –date/time –etc. u Examine the tasks carried out using the information u Examine results or reports created using the information

“DOK 322 DBMS” Y.T. Database Design Process F Conceptual Model –Merge the collective needs of all applications –Determine what Entities are being used u Some object about which information is to maintained –What are the Attributes of those entities? u Properties or characteristics of the entity u What attributes uniquely identify the entity –What are the Relationships between entities u How the entities interact with each other?

“DOK 322 DBMS” Y.T. Database Design Process F Logical Model –How is each entity and relationship represented in the Data Model of the DBMS u Hierarchic? u Network? u Relational? u Object-Oriented?

“DOK 322 DBMS” Y.T. Database Design Process F Internal Model –Choices of index file structure –Choices of data storage formats –Choices of disk layout

“DOK 322 DBMS” Y.T. Database Design Process F External Model –User views of the integrated database –Making the old (or updated) applications work with the new database design

“DOK 322 DBMS” Y.T. Developing a Conceptual Model F Overall view of the database that integrates all the needed information discovered during the requirements analysis. F Elements of the Conceptual Model are represented by diagrams, Entity-Relationship or ER Diagrams, that show the meanings and relationships of those elements independent of any particular database systems or implementation details.