systems analysis

Systems Analysis

IDEF0 and IDEF1.x

Systems Analysis

Moving from IDEF0 to IDEF1.xTechnique for describing information

structuresInformation models represent:

things - entitiesproperties of things - attributesassociations between things -

relationships

Entities

Abstractions of real world thingseg CUSTOMER

does not relate to specifict customers ...any distinguishable person, place, thing, event or

concept about which information is kept. (Bruce 1992)

Specificcustomer

A

AA

Attributes

Each set of data for an entity may be regarded as an ‘instance’ of that entitiy

The individual pieces of data for an instance are called attributesA

Customer

NameAddressTel No.Credithistory

Relationships

Imagine two entities: Lecturer and Student

Lecturers teach studentsTeaching is the “relationship”

between the two abstract entities

Types of Information Model

Entity Relationship Model: shows major entities and relationships - wide business area

Key Based Models: Third normal form model that describes major data structures (entities, keys and sample attributes) - wide business area

Types of Information Model

Project Information Model: describes a portion of an overall data structure - specific to a development project

Fully Attributed Model: third (or higher) normal form model (entities, attributes, relationships and integrity rules) - single project

IDEF1.x - Components

Entity

Entity Names are instances - each instance represents a customer not multiple customers

Area above line is for key attributesArea below line if for non-key attributes

Entity Name

Primary Key Area

Data Area

Relationships

Relationships are connections or links between entities

LECTURER STUDENTteaches

One to Many

Relationships

Non-identifying Relationship

LECTURER STUDENTteacheslecturer-no student-no

lecturer-no (FK)

Relationships

Identifying Relationship

BOOK

BOOK-COPY

classmarkcopy-noclassmark (FK)

Relationships

Resolving many to many linksA person may use more than one

address, an address may be used by more than one personPERSON ADDRESS

person-id address-id

ADDRESS-USAGEperson-id (FK)address-id (FK)usage-type

may use used by

CardinalityIdentifying Relationship

P

Z

N

One to Zeroor more

One to Oneor more

One to Zeroor One

One to exactlyN

P

Z

N

Non-identifying Relationship

Cardinality

Example - Zero or One to One or more relationship

salesperson-id

order-no

salesperson-id (FK)

P

receives credit for

SALESPERSON

ORDER

Generating IDEF1.x

ReceivePurchaseRequest

WorksheetPack

BuyingKnowledge

Quotes

EstablishSupplier

CompletedWorksheetPack

Activity Model

QUOTESWORKSHEET-PACKAGE

Information model

Information model

QUOTES

OPERATIONS

LAYOUTS

WORKSHEET

DRAWINGS

GuidelinesCreate activity dia of business processFrom the info flows, create entity poolCreate entities on information modelInvestigate detail of aggregate entitiesDraw relationships between entitiesResolve many-to-many linksInsert keys and specify identifying/non-

identifying relationshipsValidate with users