8/28/97information organization and retrieval database design university of california, berkeley...

8/28/97 Information Organization and Retrieval

Database Design

University of California, Berkeley

School of Information Management and Systems

SIMS 202: Information Organization and Retrieval


Review

• Database Data Models

• Database Design Process

• Basics of ER Diagrams


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 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?


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

• Examples derived from David R. McClanahan “Conceptual Design” DBMS Magazine January 1992, and “Hands-on Design”, February 1992.


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

ProjectEvaluationEmployee

Manager

1/n/n

1/1/1

n/n/1

ManagesEmployee

ProjectAssignedEmployee 4(2-10) 1

SSN ProjectDate

Manages

Is Managed By

1

n


Today

• More on Entity-Relationship Diagrams

• Designing a database


Weak Entities

• Owe existence entirely to another entity

Order-lineContainsOrder

Invoice #

Part#

Rep#

QuantityInvoice#


Supertype and Subtype Entities

ClerkIs one ofSales-rep

Invoice

Other

Employee

Sold

Manages


Many to Many Relationships

Employee

ProjectIsAssigned

ProjectAssignment

Assigned

SSN

Proj#

SSN

Proj#Hours


Developing a Conceptual Model

• We will look at a small business

• Assume that we have done interviews with the business and found out the following information about the forms used and types of information kept in files and used for business operations...


Primary Business Operations

• The business sells parts to customers.– Each part has:

• A part number,

• A selling price,

• A description of the part,

• The count of the part currently in stock.


Business Operations (cont.)

• Each sale is on an invoice to one customer.– Invoices contain:

• Line items for each part ordered,

• Total amount due for the invoice,

• Customer information:– Company name, address, and an ID number.

– Invoices are written up by one sales representative, who is credited with the sale

• Sales reps are paid a 5% commission on sales.



• Information must be kept on inventory of parts.

• There are multiple suppliers of parts:– The prices charged by different suppliers for a

given part may be different. This is the Cost of the part.



• Employee information includes:– Name,– Social Security Number,– Employee ID number,– Address,– Position.

• Hourly wages must be tracked for all employees (except sales reps).



• One account is kept for each customer to track charges, payments, and the current balance.

• The company needs to know if an order has been shipped.

• The accounting department must know which invoices have been paid.

• The total sales for each sales rep must be calculated.


Business Operations (cont.)• We must know if a part is in stock at the company or

on order from a supplier.• Each hourly employee generates a time-card every

Monday morning.• Sales Reps don’t turn in time-cards, just their total

sales.• All employees are paid weekly by check.• We need a report each Monday telling us what each

employee should be paid for the previous week.


Entities

• Customer• Invoice• Employee• Inventory• Supplier• Account• Sales Rep• Parts

• Timecard• Check


Functional areas

• Ordering• Inventory• Supplies• Shipping• Personnel• Payroll• We will concentrate on Ordering and

Inventory


Ordering

InvoiceRep-custinvoiceSales-Rep

Customer

Simple TernaryRelationship


Ordering

InvoiceOrdersCustomer

Cust# Writes

Sales-Rep

Invoice#

Rep#

Parts Repeatingattribute


Ordering Normalization

OrdersCustomer

Cust#

Invoice

Writes

Sales-Rep

Invoice#

Rep#

Rep#

Line-ItemContains

Part#

QuantityInvoice#

Cust#


Parts and Suppliers

PartSuppliesSupplier

Company# Includes

Line-Item

Part#

Part#

Count

Price

Invoice#

m nIs this correct?Where does Pricebelong?


Parts and Suppliers(alternative 2)

Company#

Contains

Line-ItemPart# Invoice#

Part

Part# Count

Price

n

m

Supplier

Company#

Offers

Supplied-Part

Part# Cost

Supplies

IntersectionEntity


Parts and Suppliers (Alternative 3)

Company#

Contains


Part

Part# Count

Price

Supplier

Company#

Supplies

Supplied-Part

Part# Cost


Parts and Suppliers(Alternative Notation 4)

Company#

Contains


Part

Part# Count

Price

mSupplier

Company#

Part# Cost

Supplying


Parts and Suppliers(Alternative Notation 5)

Part

Part# Count

Price

mSupplier

Company# Cost

Supplies


ER Model

OrdersCustomer

Cust#

Invoice

Writes

Sales-Rep

Invoice#

Sales

Rep#

Line-ItemContains

Part#

QuantityInvoice#

Cust#Contains

Part

Part# Count

Price

Supplier

Company#

OrderedPart

Hourly

Employee

ISA

Emp#Wage

Company#

Part# Cost

SuppliedPart

Has

On-Order

Supplies

Company#

Part# Quantity


Next Time

• More on normalization

• Effectiveness and Efficiency criteria for database designs

• Advantages and failings of DBMS technology

8/28/97information organization and retrieval database design university of california, berkeley...

Documents

information organization

retrieval slide

needed information

retrieval entity

information persons

simple model

data structures

chains of data