8/28/97Information Organization and Retrieval Files and Databases University of California, Berkeley...

8/28/97 Information Organization and Retrieval

Files and Databases

University of California, Berkeley

School of Information Management and Systems

SIMS 202: Information Organization and Retrieval


Review

• MELVYL access issues

• bibliographic description and rules


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.


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)


Database Data Models

• Hierarchical Model– Similar to data structures in programming

languages.Books

(id, title)

Publisher SubjectsAuthors

(first, last)



• Network Model– Provides for single entries of data and

navigational “links” through chains of data.

Subjects Books

Authors

Publishers



• Relational Model– Provides a conceptually simple model for data

as relations (typically considered “tables”) with all data visible.

Book ID Title pubid Author id1 Introductio 2 12 The history 4 23 New stuff ab 3 34 Another title 2 45 And yet more 1 5

pubid pubname1 Harper2 Addison3 Oxford4 Que

Authorid Author name1 Smith2 Wynar3 Jones4 Duncan5 Applegate

Subid Subject1 cataloging2 history3 stuff

Book ID Subid1 22 13 34 24 3



• Object Oriented Data Model– Encapsulates data and operations as “Objects”

Books(id, title)

Publisher SubjectsAuthors

(first, last)


Database Design Process

ConceptualModel

LogicalModel

External Model

Conceptual requirements




Application 1

Application 1

Application 2 Application 3 Application 4

Application 2

Application 3

Application 4

External Model

External Model

External Model

Internal Model


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



• 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?



• Logical Model– How is each entity and relationship represented

in the Data Model of the DBMS• Hierarchic?

• Network?

• Relational?

• Object-Oriented?



• Internal Model– Choices of index file structure– Choices of data storage formats– Choices of disk layout



• External Model– User views of the integrated database – Making the old (or updated) applications work

with the new database design


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.


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


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


Relationships

• Relationships are the associations between entities. They can involve one or more entities and belong to particular relationship types


Relationships

ClassAttendsStudent

PartSuppliesproject

partsSupplier

Project


Types of Relationships

• Concerned only with cardinality of relationship

TruckAssignedEmployee

ProjectAssignedEmployee

ProjectAssignedEmployee

1 1

n

n

1

m


More Complex Relationships

ProjectAssignedEmployee 4(2-10) 1

ProjectEvaluationEmployee

Manager

1/n/n

1/1/1

n/n/1

ManagesEmployee

SSN ProjectDate

Manages

Is Managed By

1

n


Next Time

• More on Entity-Relationship Diagrams

• Designing a database

8/28/97Information Organization and Retrieval Files and Databases University of California, Berkeley...

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