Network Modelling

8/3/2019 Network Modelling

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Network Modeling

The chapter will address the followingquestions:Why may network modeling become an important skill for

applications developers in the next several years?What is the description network modeling and explain why it

is important?

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

How can you factor a systems or applications locations intocomponent locations using a special location decompositiondiagram?

How can you document the connections and essential dataflows between locations using location connectivity diagrams(LCDs)?

Introduction


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Introduction

The chapter will address the following questions:

What is the complementary relationship between network, process,

and data models?

How can you synchronize data, process, interface, and networkmodels to provide a complete and consistent logical system

specification?

How is network modeling useful in different types of projects and

phases?


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Network Modeling - Not Just For ComputerNetworks

Computer Networks

Have become the nervous system of todays information systems.

The computer network is aphysical component of an information

system. Must be created to support the logical distribution of data,

processes, and interfaces of an information system.

Network modeling is a technique for documenting the

geographic structure of a system. Synonyms include

distribution modeling and geographic modeling.


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Networks: Structure

Communication Sub-Network (Backbone):

Switching / Communication

Client

Client

Server

LAN

Access / Information Service

Sub-Network

Client

Client

Client

ClientConnections


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INFORMATION SYSTEMS FRAMEWORK

S

Y

S

T

EM

A

N

A

L

Y

S

T

S

SYSTEM

BUILDERS

(components)

SYSTEM

DESIGNERS

(specification)

SYSTEM

USERS

(requirements)

SYSTEM

OWNERS

(scope)

Database

Technology

(and standards)

Data Requirements

FOCUS ON

SYSTEM

DATA

Business Processes

FOCUS ON

SYSTEM

PROCESSES

Interface Requirements

FOCUS ON

SYSTEM

INTERFACES

Software

(and Hardware)

Technology

(and standards)

Interface

Technology

Networking

Telchnology

(and standards)

Communication Reqts.

Location Connectivity

Operating Locations

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

EDICust

St.

LouisHQ

LAOffice

IndyWare-house

NYOffice

WestCustomers

East

Customers

MaintenanceRecords

ProductsCatalog

ordercatalog

changes

shiporder

shiporder shiporder

credit credit

service


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Network Modeling - Not Just For ComputerNetworks

Computer Networks

The need for network modeling is being driven by a technical trend

distributed computing.

Distributed computing is the assignment of specificinformation 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.

The distributed computers include: desktop and laptop computers, sometimes called clients

shared network computers, called servers

legacy mainframe computers and minicomputers


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System Concepts For Network Modeling

Todays systems analyst must seek answers to new

questions:

What locations are applicable to this information system or

application? How many users are at each location?

Do any users travel while using (or potentially using) the system?

Are any of our suppliers, customers, contractors, or other external

agents to be considered locations for using the system?

What are the users data and processing requirements at eachlocation?

How much of a locations data must be available to other

locations? What data is unique to a location?


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Todays systems analyst must seek answers to new

questions: (continued)

How might data and processes be distributed between locations?

How might data and processes be distributed within a location?

A network modeling tool is needed to document what

we learn about a business systems geography and

requirements.

Network modeling is a diagrammatic technique used to documentthe shape of a business or information system in terms of its

business locations.


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Business Geography

Logical network modeling is the modeling of business network

requirements independent of their implementation.

All information systems have geography. The location connectivity diagram (LCD) models system

geography independent of any possible implementation.

A location connectivity diagram (LCD) is a logical network

modeling tool that depicts the shape of a system in terms of its

user, process, data, and interface locations and the necessaryinterconnections between those locations.


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Suppliers

(275)

Buyers

(20)

on-the-road

Accounts

Payable

Office

(Atlanta)

Central

Warehouse

(Atlanta)

Inventory Control

Manager's Office

(Atlanta)

Purchasing

Clerks

(3)

Atlanta

Distribution

Center

(New York)

Distribution

Center

(Chicago)

Distribution

Center

(Los Angeles)


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Business Geography

The location connectivity diagram (LCD) illustrates two concepts

locations and connectivity.

The concept of geography is based on locations. 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.

Business management and users will tend to identify logical

locations where people do work or business.

Information technologists will tend to discussphysical

locations where computer and networking technology is

located.

Location


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Business Geography

Example locations include:

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

City Computer center

Campus Network server

Building PC or terminal location

Office Local area network

Work area (e.g., warehouse)

Wide area network hub/gateway Subsidiary

Home office

Customer, supplier, or contractor


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Business Geography

Logical locations can be:

scattered throughout the business for any given information

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.

Logical locations can represent: clusters of similar locations

organizations and agents outside of the company but which

interact with or use the information system; possibly (and

increasingly) as direct users


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Business Geography

Derivatives of the rectangle will be used to illustrate different types

of locations.

The standard rectangle will be used to represent a specificlocation.

The rectangle with the double, vertical lines will be used to

represent a cluster of locations.

Some locations are not stationary, a rounded rectangle will

represent their mobility. Some locations represent external organizations and agents

(such as customers, suppliers, taxpayers, contractors, and the

like). A parallelogram to illustrate these external locations.

Specific

Location

Moving or Mobile

Location(s)

Cluster

of "like"

locations

External

Location


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Business Geography

Location names should describe the location and/or its users.

Examples of location names follows:

Paris, France Indianapolis, Indiana Grissom Hall Building 105 Grant Street building Room 222

Warehouse Rooms 230-250 Shipping Dock

Order Clerk User names (as locations) Order Entry Dept.

Customers Order clerks (a cluster) Suppliers

Students


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Business Geography

Some locations consist of other locations and clusters.

It can be quite helpful to understand the relative decomposition of

locations and types of location. Decomposition is the act of breaking a system into its

component subsystems. Each level ofabstraction reveals

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

subset of that system.

In systems analysis, decomposition allows you to partition asystem into logical subsets of locations for improved

communication, analysis, and design.

A location decomposition diagram shows the top down

geographic decomposition of the business locations to be

included in a system.


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Inventory

Control

SystemGeography

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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Business Geography

The purpose of network modeling is to help system designers

distribute the technical data, processes, and interfaces across the

computer network.

The systems analyst needs to specify the technology-independent

communications that must occur between business locations.

The communication between business locations requires

connectivity.

Connectivity defines the need for, and provides the means fortransporting essential data, voice, and images from one location

to another.

Connections between locations represent the possibility of data

flows between locations.


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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

There are no universal standards for location connectivity

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

Network, data, interface, and process models represent different

views of the same system, but these views are interrelated.

Modelers need to synchronize the different views to ensureconsistency and completeness of the total system specification.


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Data and Process Model Synchronization:

There should be one data store in the process models for each

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

The synchronization quality check is stated as follows:

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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Entity . Attribute ProcessCustomerApplication

ProcessCustomerCredit

Application

ProcessCustomerChangeof

Address

ProcessInternalCustomerCredit

Change

ProcessNewCustomerOrder

ProcessCustomerOrder

Cancellation

ProcessCustomerChangeto

OutstandingOrder

ProcessInternalChangeto

CustomerOrder

ProcessNewProductAddition

ProcessProductWithdrawlfrom

Market

ProcessProductPriceChange

ProcessChangetoProduct

Specification

ProcessProductInventroy

Adjustment

Customer C C R R R R

.Customer Number C C R R R R

.Customer Name C C U R R R

.Customer Address C C U RU RU RU

.Customer Credit Rating C U R R R

.Customer Balance Due RU U R R

Order C D RU RU

.Order Number C R R

.Order Date C U U

.Order Amount C U U

Ordered Product C D CRUD CRUD RU.Quantity Ordered C CRUD CRUD

.Ordered Item Unit Price C CRUD CRUD

Product R R R R C D RU RU RU

.Product Number R R R R C R

.Product Name R R R C RU

.Product Description R R R C RU

.Product Unit of Measure R R R C RU RU

.Product Current Unit Price R R R U

.Product Quantity on Hand RU U RU RU RU


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Data and Network Model Synchronization: (continued)

System analysts have found it useful to define logical

requirements in the form of aData-to-Location-CRUDmatrix. A Data-to-Location-CRUD Matrix is a table in which the rows

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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Entity . Attribute Customers

KansasCity

.Marketing

.Advertsing

.Warehouse

.Sales

.Accounts

..

Receivable

Boston

.Sales

.Warehouse

SanFrancisco

.Sales

SanDiego

.Warehose

Customer INDV ALL ALL SS SS SS SS

.Customer Number R R CRUD R CRUD R CRUD R

.Customer Name RU R CRUD R CRUD R CRUD R

.Customer Address RU R CRUD R CRUD R CRUD R

.Customer Credit Rating X R RU R R

.Customer Balance Due R R RU R R

Order INDV ALL SS ALL SS SS SS SS

.Order Number SRD R CRUD R CRUD R CRUD R CRUD R

.Order Date SRD R CRUD R CRUD R CRUD R CRUD R

.Order Amount SRD R CRUD CRUD R CRUD R CRUD R

Ordered Product INDV ALL SS ALL SS SS SS SS

.Quantity Ordered SUD R CRUD R CRUD R CRUD CRUD

.Ordered Item Unit Price SUD R CRUD CRUD R CRUD CRUD

Product ALL ALL ALL ALL ALL ALL ALL ALL ALL

.Product Number R CRUD R R R R R R R

.Product Name R CRUD R R R R R R R

.Product Description R CRUD RU R R R R R R

.Product Unit of Measure R CRUD R R R R R R R

.Product Current Unit Price R CRUD R R R R R R

.Product Quantity on Hand X RU R R RU R RU

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

S = submit C = create R = read U = update D = delete


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Process and Interface Model Synchronization:

The context diagram was previously introduced as an interface

model that documents how the system you are developinginterfaces to business, other systems, and other organizations.

Data flow diagramsdocument the systems process response to

various business and temporal events.

Both models should be synchronized.


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Process and Network Model Synchronization:

Process models illustrate the essential work to be performed by

the system as a whole. Network models identify the locations where work is to be

performed.

Some work may be unique to one location. Other work may be

performed at multiple locations.

Before designing the information system, what processes mustbe performed at which locations should be identified and

documented.


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Process and Network Model Synchronization:

Synchronization of the process and network models can be

accomplished through a Process-to-Location-AssociationMatrix.

A Process-to-Location-Association Matrix is a table in which the

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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Process Custom

ers

Kansas

City

.Marketing

.Advertsing

.Warehouse

.Sales

.Acc

ountsReceivable

Boston

.Sales

.Warehouse

SanFra

ncisco

.Sales

SanDie

go

.Warehose

Process Customer Application X X X X

Process Customer Credit Application X X

Process Customer Change of Address X X X X

Process Internal Customer Credit Chnage X

Process New Customer Order X X X X

Process Customer Order Cancellation X X X X

Process Customer Change to Outstanding Order X X X X

Process Internal Change to Customer Order X X X

Process New Product Addition X

Process Product Withdrawal from Market X

Process Product Price Chnage X

Process Product Chnage to Product Specification X X

Process Product Inventory Adjustment X X X


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The Process of Logical Network Modeling

Network Modeling during Systems Analysis

During the study phase of systems analysis, a project team should

review any existing network models, logical or physical.

In the definition phase of systems analysis, network modelingbecomes more important.

If a network model already exists, it is expanded or refined to

reflect new application requirements.

If a network model does not exist, a network model should be

built from scratch.


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Looking Ahead to Systems Design

The logical application network model from systems analysis

describes business networking requirements, not technical

solutions.

In systems design, network models must become more technical

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

Like all system models, network models are dependent on

appropriate facts and information as supplied by the user

community.

Facts can be collected by sampling of existing forms and files;

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

interviews of users and management.

The fastest method of collecting facts and information, andsimultaneously constructing and verifying the process models is

Joint Application Development (JAD).

JAD uses a carefully facilitated group meeting to collect the

facts, build the models, and verify the modelsusually in one

or two full-day sessions.


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Computer-Aided Systems Engineering (CASE) for

Network Modeling

Network models should be stored in the repository.

Computer-aided systems engineering (CASE) technology providesthe repository for storing various models and their detailed

descriptions.


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How to Construct Logical Network Models

Location Decomposition Diagram

Decomposition diagrams are used to logically decompose and

group locations.

Building The Location Decomposition Diagram First, brainstorm your locations. Think of all of the places where

direct and indirect users of your system will be located.

To group locations in the decomposition diagram, keep similar

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

Clustering reduces clutter through simplification; however, there isa 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

Indianapolis

Marketing

Office

Advertising

OfficeSales Office

Baltimore SeattleProspective

MembersMembers

Warehouse

Order Entry

Clerks

Sales

Managers

Sales Office Warehouse

Order Entry

Clerks

Sales

Managers

Sales Office

Order Entry

Clerks

Sales

Managers

Portland

Warehouse


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How to Construct Logical Network Models

Location Connectivity Diagram

Location connectivity diagrams can be initially drawn at a 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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Members

ProspectiveMembers

Seattle

Portland

Baltimore

Indianapolis

indeterminate distance

indeterminate distance

2250 miles

2250 miles

575 miles


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Balt. Order Entry

Clerks (8)

Indpls. Order EntryClerks (12)

Indpls. AdvertisingOffice (4)

Indpls. MarketingOffice (3)

Seattle SalesManagers (2)

Seattle Order EntryClerks (7)

Members (n)

Balt. Sales

Managers (2)

Members (n)

Port. WarehouseStations (2)

Balt. Warehouse

Stations (3)

Indpls. Warehous eStations (3)

Indpls. SalesManagers (3)

Members (n)

ProspectiveMembers (n)

Figure 7.10

Indeterminate Distance

Indeterminate Distanc e

2250 miles

575 miles

250 feet

50 feet

< 150 feet

200 miles


< 40 feet

< 20 feet


< 50 feet

580 feet

2250 miles

2800 miles

575 miles


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The Next Generation

The Next Generation

The demand for logical network modeling skills will remain strong

so long as the trend towards distributed computing remains strong.

CASE tool support will evolve after methodologies, since CASE

tool engineers are reluctant to invest time and effort prior to some

semblance of a widely accepted methodological standard.

Network Modelling

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