8/28/97Information Organization and Retrieval Files and Databases University of California, Berkeley School of Information Management and Systems SIMS 202: Information Organization and Retrieval

8/28/97Information Organization and Retrieval Review MELVYL access issues bibliographic description and rules

8/28/97Information Organization and Retrieval Files and Databases File: A collection of records or documents dealing with one organization, person, area or subject. (Rowley) –Manual (paper) files –Computer files Database: A collection of similar records with relationships between the records. (Rowley) –bibliographic, statistical, business data, images, etc.

8/28/97Information Organization and Retrieval Database A Database is a collection of stored operational data used by the application systems of some particular enterprise. (C.J. Date) –Paper “Databases” Still contain a large portion of the world’s knowledge –File-Based Data Processing Systems Early batch processing of (primarily) business data –Database Management Systems (DBMS)

8/28/97Information Organization and Retrieval Database Data Models Hierarchical Model –Similar to data structures in programming languages. Books (id, title) PublisherSubjects Authors (first, last)

8/28/97Information Organization and Retrieval Database Data Models Network Model –Provides for single entries of data and navigational “links” through chains of data. SubjectsBooks Authors Publishers

8/28/97Information Organization and Retrieval Database Data Models Relational Model –Provides a conceptually simple model for data as relations (typically considered “tables”) with all data visible.

8/28/97Information Organization and Retrieval Database Data Models Object Oriented Data Model –Encapsulates data and operations as “Objects” Books (id, title) PublisherSubjects Authors (first, last)

8/28/97Information Organization and Retrieval 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

8/28/97Information Organization and Retrieval Database Design Process Conceptual Requirements –Systems Analysis Process Examine all of the information sources used in existing applications Identify the characteristics of each data element –numeric –text –date/time –etc. Examine the tasks carried out using the information Examine results or reports created using the information

8/28/97Information Organization and Retrieval Database Design Process Conceptual Model –Merge the collective needs of all applications –Determine what Entities are being used Some object about which information is to maintained –What are the Attributes of those entities? Properties or characteristics of the entity What attributes uniquely identify the entity –What are the Relationships between entities How the entities interact with each other?

8/28/97Information Organization and Retrieval Database Design Process Logical Model –How is each entity and relationship represented in the Data Model of the DBMS Hierarchic? Network? Relational? Object-Oriented?

8/28/97Information Organization and Retrieval Database Design Process Internal Model –Choices of index file structure –Choices of data storage formats –Choices of disk layout

8/28/97Information Organization and Retrieval Database Design Process External Model –User views of the integrated database –Making the old (or updated) applications work with the new database design

8/28/97Information Organization and Retrieval Developing a Conceptual Model Overall view of the database that integrates all the needed information discovered during the requirements analysis. 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.

8/28/97Information Organization and Retrieval Entity An Entity is an object in the real world (or even imaginary worlds) about which we want or need to maintain information –Persons (e.g.: customers in a business, employees, authors) –Things (e.g.: purchase orders, meetings, parts, companies) Employee

8/28/97Information Organization and Retrieval Attributes Attributes are the significant properties or characteristics of an entity that help identify it and provide the information needed to interact with it or use it. (This is the Metadata for the entities.) Employee Last Middle First Name SSN Age Birthdate Projects

8/28/97Information Organization and Retrieval Relationships Relationships are the associations between entities. They can involve one or more entities and belong to particular relationship types

8/28/97Information Organization and Retrieval Relationships Class Attends Student Part Supplies project parts Supplier Project

8/28/97Information Organization and Retrieval Types of Relationships Concerned only with cardinality of relationship Truck Assigned Employee Project Assigned Employee Project Assigned Employee 11 n n 1 m

8/28/97Information Organization and Retrieval More Complex Relationships Project Assigned Employee 4(2-10)1 Project Evaluation Employee Manager 1/n/n 1/1/1 n/n/1 Manages Employee SSNProjectDate Manages Is Managed By 1 n

8/28/97Information Organization and Retrieval Next Time More on Entity-Relationship Diagrams Designing a database