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

Network Modeling
Introduction



The chapter will address the following questions:










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 system’s or application’s locations into
component locations using a special location decomposition
diagram?
How can you document the connections and essential data flows
between locations using location connectivity diagrams (LCDs)?

1

Network Modeling
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 network
models to provide a complete and consistent logical system
specification?
How is network modeling useful in different types of projects and
phases?

2


Network Modeling

Network Modeling - Not Just For Computer
Networks


Computer Networks




Have become the nervous system of today’s information systems.
The computer network is a physical 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.

3


Network Modeling
INFORMATION SYSTEMS FRAMEWORK
FOCUS ON
SYSTEM
DATA

FOCUS ON
SYSTEM
PROCESSES

FOCUS ON
SYSTEM
GEOGRAPHY

FAST

Methodology

Operating Locations

Survey Phase
(establish scope &
project plan)

FOCUS ON
SYSTEM
INTERFACES

SYSTEM
OWNERS
(scope)

Location Decomposition

Data Requirements

Business Processes

Interface Requirements

Communication Reqts.
EDI
Cust

S
Y

S
T
E
M
A
N
A
L
Y
S
T
S

SYSTEM
USERS

or der

St.
Louis
HQ

ship
order

West
Cust omers

cat alog
changes

Products
Catalog

East
Cust om ers
cr edit

credit

LA
Off ice

(requirements)

Study Phase
(etablish system
improvemetn
objectives)

ship
order

Indy
Warehouse

ship order

NY
Office

service
Maint enance
Records

Logical Data Model

Logical Process Model

Logical Interface Model

Location Connectivity
Diagram

SYSTEM
DESIGNERS
(specification)

SYSTEM
BUILDERS
(components)

Database
Technology
(and standards)

Software
(and Hardware)
Technology

Interface
Technology

Networking
Telchnology

(and standards)
(and standards)

(and standards)

4

Definition Phase
(establish and
prioritize
business system
requirements)


Network Modeling

Network Modeling - Not Just For Computer
Networks


Computer Networks


The need for network modeling is being driven by a technical

trend – distributed computing.
 Distributed computing is the assignment of specific
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.
 The distributed computers include:
• desktop and laptop computers, sometimes called clients
• shared network computers, called servers
• legacy mainframe computers and minicomputers

5


Network Modeling
System Concepts For Network Modeling



Today’s 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 user’s data and processing requirements at each
location?
How much of a location’s data must be available to other
locations? What data is unique to a location?

6


Network Modeling
System Concepts For Network Modeling



Today’s 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 system’s geography and
requirements.


Network modeling is a diagrammatic technique used to document
the shape of a business or information system in terms of its
business locations.

7


Network Modeling
System Concepts For Network Modeling



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 necessary
interconnections between those locations.

8


Network Modeling
Buyers
(20)
on-the-road

Suppliers
(275)

Purchasing
Clerks
(3)
Atlanta

Accounts
Payable
Office
(Atlanta)

Inventory Control
Manager's Office
(Atlanta)

Central
Warehouse

(Atlanta)

Distribution
Center
(New York)

Distribution
Center
(Chicago)

9

Distribution
Center
(Los Angeles)


Network Modeling
System Concepts For Network Modeling



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.

Location





Business management and users will tend to identify logical
locations where people do work or business.
Information technologists will tend to discuss physical
locations where computer and networking technology is
located.

10


Network Modeling
System Concepts For Network Modeling



Business Geography


Example locations include:
Logical locations – places where data are
collected, work is performed, or
information is needed
• City

• Campus
• Building
• Office
• Work area (e.g., warehouse)
• Subsidiary
• Home office
• Customer, supplier, or contractor

11

Implementation Locations – places
where computers, peripherals, and other
information technology is located
• Computer center
• Network server
• PC or terminal location
• Local area network
• Wide area network hub/gateway


Network Modeling
System Concepts For Network Modeling



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
12


Network Modeling
System Concepts For Network Modeling



Business Geography


Specific
Location

Cluster
of "like"
locations

Moving or Mobile
Location(s)

External
Location

Derivatives of the rectangle will be used to illustrate different
types of locations.
 The standard rectangle will be used to represent a specific
location.
 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.

13


Network Modeling
System Concepts For Network Modeling



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

14


Network Modeling
System Concepts For Network Modeling



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’ of abstraction 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 a
system 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.
15


Network Modeling
Inventory
Control
System
Geography

Atlanta
Headquarters

Inventory
Control
Manager

Purchasing
Agents
(4)

Accounts
Payable
Managers
(2)

New York
Distribution
Center

Accounts
Payable
Office

Los Angeles
Distribution
Center

Buyers
(15-25)

Accounts
Payable
Clerks
(3)

16

Chicago
Distribution
Center


Network Modeling
System Concepts For Network Modeling



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 for
transporting essential data, voice, and images from one location

to another.
Connections between locations represent the possibility of data
flows between locations.
17


Network Modeling

Buyers
(15-25)
Chicago
Distribution
Center

Purchasing
Agents
(4)

Los Angeles
Distribution
Center

New York
Distribution
Center

Suppliers

Accounts
Payable

Managers
(2)

Accounts
Payable
Clerks
(3)

18

Inventory
Control
Manager


Network Modeling
System Concepts For Network Modeling



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.

19

Network Modeling
System Concepts For Network Modeling



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 ensure
consistency and completeness of the total system specification.

20


Network Modeling
System Concepts For Network Modeling



Synchronizing of System Models


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 in

the 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.

21


R

R

R

.Customer Name

C

C

U

R

R

R

.Customer Address

C

C

U

RU

RU

RU

R

R

.Customer Credit Rating

C

U

.Customer Balance Due
Order

R
RU

U

R

R

C

D

RU

RU

.Order Number

C

R

R

.Order Date

C

U

U

.Order Amount

C

U

U

CRUD

CRUD

CRUD

CRUD

C

Ordered Product
.Quantity Ordered

C

.Ordered Item Unit Price

C

D

Process Product Invent roy
Adjust ment

Process Int ernal Change t o
Cust omer Order

R

R

Process Change t o Product
Specificat ion

Process Cust omer Change t o
Out st anding Order

R

R

Process Product Price Change

Process Cust omer Order
Cancellat ion

R

C

Process Product Wit hdrawl from

Market

Process New Cust omer Order

C

C

Process New Product Addit ion

Process Cust omer Credit
Applicat ion

C

.Customer Number

Entity . Attribute
Customer

Process Cust omer Change of
Address

Process Cust omer Applicat ion

Process Int ernal Cust omer Credit
Change

Network Modeling

RU

RU

RU

RU

CRUD

CRUD

R

R

R

R

C

.Product Number

R

R

R

R

C

R

.Product Name

R

R

R

C

RU

.Product Description

R

R

R

C

.Product Unit of Measure

R

R

R

C

.Product Current Unit Price

R

R

R

.Product Quantity on Hand

RU

RU

RU

Product

22

U

D

RU
RU

RU

U
RU


Network Modeling
System Concepts For Network Modeling



Synchronizing of System Models


Data and Network Model Synchronization:
 A data model describes the stored data requirements for a
system as a whole.
 The network model describes the business operating locations.
 The goal is to identify what data is at which locations.
 Specifically, the following business questions might be asked:
• Which subset of the entities and attributes are needed to perform
the work to be performed at each location?
• What level of access is required?
• Can the location create, read, delete, or update instances of the
entity?

23


Network Modeling
System Concepts For Network Modeling



Synchronizing of System Models


Data and Network Model Synchronization: (continued)
 System analysts have found it useful to define logical
requirements in the form of a Data-to-Location-CRUD matrix.
• 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.

24


RU

R

CRUD

R

CRUD

R

CRUD

R

.Customer Address

RU

R

CRUD

R

CRUD

R

CRUD

R

R

RU

R

R

RU

.Customer Credit Rating
.Customer Balance Due

X
R
INDV

ALL

.Order Number

SRD

R

.Order Date

SRD

.Order Amount

. Warehose

R

.Customer Name

San Diego

CRUD

. Sales

. Warehouse

SS

R

San Francisco

. Sales

SS

CRUD

INDV

Bost on

. Sales

SS

R

. Advert sing

SS

CRUD

. Market ing

ALL

R

.Customer Number

Kansas Cit y

ALL

R

Entity . Attribute
Customer

Cust omers

. Warehouse

. Account s
……..Receivable

Network Modeling

R

R

R

SS

ALL

CRUD

R

CRUD

R

CRUD

R

SRD

R

CRUD

INDV

ALL

.Quantity Ordered

SUD

R

CRUD

.Ordered Item Unit Price

SUD

R

CRUD

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

R

R

RU

R

RU

Order

Ordered Product

Product

SS

SS

SS

SS

R

CRUD

R

CRUD

R

CRUD

R

CRUD

R

CRUD

R

CRUD

R

CRUD

R

CRUD

R

SS

SS

SS

SS

SS

ALL

R

CRUD

R

CRUD

CRUD

R

CRUD

RU

INDV = individual

ALL = ALL

SS = subset

X = no access

S = submit

C = create

R = read

U = update

25

CRUD
CRUD

D = delete