Systems analysis and design methods 7th whitten and benley chapter 07

Data RequirementsLogical Data Model FOCUS ON SYSTEM DATA Business Processes Logical Process Model FOCUS ON SYSTEM PROCESSES Interface Requirements Logical Interface Model FOCUS ON SYSTEM

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Network Modeling

Introduction

 The chapter will address the following questions:

applications developers in the next several years?

important?

 What is the definition of a system in terms of locations, location types, and clusters?

component locations using a special location decomposition

diagram?

between locations using location connectivity diagrams (LCDs)?

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Introduction

 The chapter will address the following questions:

process, and data models?

models to provide a complete and consistent logical system

specification?

phases?

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Network Modeling - Not Just For Computer

Networks

system

 Must be created to support the logical distribution of data,

processes, and interfaces of an information system

geographic structure of a system Synonyms include

distribution modeling and geographic modeling

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Data Requirements

Logical Data Model

FOCUS ON SYSTEM DATA

Business Processes

Logical Process Model

FOCUS ON SYSTEM PROCESSES

Interface Requirements

Logical Interface Model

FOCUS ON SYSTEM INTERFACES

Software (and Hardware) Technology (and standards)

Interface Technology (and standards)

Networking Telchnology (and standards)

Communication Reqts.

Location Connectivity Diagram

Operating Locations

Location Decomposition

FOCUS ON SYSTEM GEOGRAPHY

Definition Phase (establish and prioritize business system requirements)

Study Phase (etablish system improvemetn objectives)

Survey Phase (establish scope & project plan)

FAST

Methodology

EDI St

Louis HQ

LA Off ice Indy Ware- NY Office

West Cust omers

East Cust omers

Maint enance Records

Products Catalog

order cat alog

ship

ship ship order credit credit

service

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Network Modeling - Not Just For Computer

Networks

trend – distributed computing

information system elements to different computers which cooperate and interoperate across computer network A

synonym is client/server computing; however, client/server is

actually one style of distributed computing

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System Concepts For Network Modeling

 Today’s systems analyst must seek answers to new

questions:

application?

agents to be considered locations for using the system?

location?

locations? What data is unique to a location?

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 Today’s systems analyst must seek answers to new

questions: (continued)

 A network modeling tool is needed to document what

we learn about a business system’s geography and

requirements

the shape of a business or information system in terms of its

business locations

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requirements independent of their implementation

geography independent of any possible implementation

modeling tool that depicts the shape of a system in terms of its user, process, data, and interface locations and the necessary interconnections between those locations

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Suppliers

(275)

Buyers (20) on-the-road

Accounts Payable Office (Atlanta)

Distribution Center (New York)

Distribution Center (Chicago)

Distribution Center (Los Angeles)

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– locations and connectivity

• A location is any place at which users exist to use or interact with

the information system or application It is also any place where business can be transacted or work performed.

locations where people do work or business

locations where computer and networking technology is located

Location

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Logical locations – places where data are

collected, work is performed, or

information is needed

Implementation Locations – places

where computers, peripherals, and other information technology is located

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system

 on the move (e.g., traveling sales representatives)

 external to the enterprise for which the system is being built For instance, customers can become users of an information system via the telephone or the Internet

 clusters of similar locations

interact with or use the information system; possibly (and increasingly) as direct users

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represent their mobility.

(such as customers, suppliers, taxpayers, contractors, and the like) A parallelogram to illustrate these external locations

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locations and types of location

component subsystems Each ‘level’ of abstraction reveals

more or less detail (as desired) about the overall system or a subset of that system

system into logical subsets of locations for improved

communication, analysis, and design

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Inventory Control System Geography

New York Distribution Center

Chicago Distribution Center

Atlanta Headquarters

Los Angeles Distribution Center

Inventory

Control

Manager

Purchasing Agents (4)

Accounts Payable Office

Buyers (15-25)

Accounts Payable Managers (2)

Accounts Payable Clerks (3)

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distribute the technical data, processes, and interfaces across the computer network

communications that must occur between business locations

connectivity

transporting essential data, voice, and images from one location

to another

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New York Distribution Center

Chicago Distribution Center

Los Angeles Distribution Center

Inventory Control Manager

Purchasing Agents (4)

Buyers

(15-25)

Accounts Payable Managers (2)

Accounts Payable Clerks (3) Suppliers

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 Miscellaneous Constructs

diagrams; therefore, in appropriate situations it is permissible to annotate LCDs with symbols from other models, such as data flow diagrams

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 Synchronizing of System Models

views of the same system, but these views are interrelated

consistency and completeness of the total system specification

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entity in the data model Also, there are sufficient processes in the process model to maintain the data in the data model

• Every entity should have at least one C, one R, one U, and one D

entry for system completeness If not, one or more event processes were probably omitted from the process models More importantly, users and management should validate that all possible creates, reads, updates, and deletes have been included.

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system as a whole

 The goal is to identify what data is at which locations

• Which subset of the entities and attributes are needed to perform the work to be performed at each location?

• Can the location create, read, delete, or update instances of the

entity?

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requirements in the form of a Data-to-Location-CRUD matrix.

indicate entities (and possibly attributes); the columns indicate locations; and the cells (the intersection rows and columns) document level of access where C = create, R = read or use, U = update or modify, and D = delete or deactivate.

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INDV = individual ALL = ALL SS = subset X = no access

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 The context diagram was previouslyThe introduced as an interface model that documents how the system you are developing

interfaces to business, other systems, and other organizations

various business and temporal events

 Both models should be synchronized.Both

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the system as a whole

performed

performed at multiple locations

be performed at which locations should be identified and documented

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accomplished through a Process-to-Location-Association Matrix

rows indicate processes (event or elementary processes); the columns indicate locations, and the cells (the intersection rows and columns) document which processes must be performed at which locations.

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The Process of Logical Network Modeling

 Network Modeling during Strategic Systems Planning Projects

network architecture to guide the design of all future computer networks and applications that use those networks

diagram that logically groups locations

initial mapping of data entities to locations, and processes to locations

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review any existing network models, logical or physical

becomes more important

 If a network model already exists, it is expanded or refined to reflect new application requirements

built from scratch

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describes business networking requirements, not technical

solutions

they must become physical network models that will guide the technical distribution and duplication of the other physical system components, namely, DATA, PROCESSES, and INTERFACES

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 Fact-Finding and Information Gathering for Network Modeling

appropriate facts and information as supplied by the user

community

research of similar systems; surveys of users and management; and interviews of users and management

simultaneously constructing and verifying the process models is

Joint Application Development (JAD)

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the repository for storing various models and their detailed

descriptions

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How to Construct Logical Network Models

group locations

direct and indirect users of your system will be located

locations on the same level or within the same branch of the tree

a danger of oversimplifying the model

 Cluster a location or its users if the data and processing requirements for all users are expected to be the same

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Member Services Sys Geography

Sales Managers

Order Entry Clerks

Sales Managers

Sales Office

Order Entry Clerks

Sales Managers Portland

Warehouse

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How to Construct Logical Network Models

high-level to communicate general information More detailed

information can be added to subsequent diagrams

 In the following slides, the first location connectivity diagram

drawn is a systemwide model It will include any external

locations and locations that have sublocations The second diagram reveals an exploded view

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Seattle Order Entry Clerks (7) Members (n)

Balt Sales Managers (2) Members (n)

Port Warehouse Stations (2)

Balt Warehouse Stations (3)

Indpls Warehouse Stations (3)

Indpls Sales Managers (3) Members (n)

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The Next Generation

so long as the trend towards distributed computing remains strong

tool engineers are reluctant to invest time and effort prior to some semblance of a widely accepted methodological standard

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