MIT5312: Professor KirsModeling Tools Slide 1 Modeling Tools

MIT5312: Professor Kirs Modeling Tools Slide 1

Modeling Tools


TOPICSTOPICS Systems Concepts

• Why??? Modeling Diagram Conventions

• The Rules of the Game Modeling Diagrams

• Basic Principles• Context Diagrams• Decomposition Diagrams• Data Flow Diagrams


Information Environment

Systems Concepts• Systems Thinking

• Application of formal Systems theory and concepts

Information System

INPUTS

Business Environment

Operating EnvironmentBusiness Strategy

Government Mandates

Organization Policies

OUTPUTS

• The Information Environment• Constantly changing along

with Social, Business and Organizational changes

• The Information System• The Collection of inter-

related systems/packages

• System Inputs• Data from the Organization,

external sources, other systems, or self-generated

• System Outputs• Reports, Screens, Files, Data

to other systems, etc.

Feedback and Control Loop

• Feedback & Control Loop• Self-Monitoring &Modification

(Thermostatic Control)


Systems Concepts• Systems Thinking• Process Concepts

• Historically, IS were focused on individual business functions

Sales Production

Marketing

Service

Finance Accounting

• IS were developed for each functional Area

Marketing IS Finance IS Accounting IS

Sales IS Service IS Production IS

INPUTS

OUTPUTS

INPUTS

OUTPUTS

INPUTS

OUTPUTS

INPUTS

OUTPUTS

INPUTS

OUTPUTS

INPUTS

OUTPUTS

• Each IS was intended to process or transform the inputs to outputs



• It later became obvious that some functions were inter-related, and Cross-functional IS were needed

INPUTS

INPUTS

Marketing

Marketing IS

Accounting

Accounting IS

Sales

Sales IS

Finance

Finance IS

INPUTS

INPUTS

Cross-Functional IS

to get input from each functional area,Process it, and return it to the individual functional systems as input



• The emphasis today is to have an Enterprise Model which will encompass the entire organization (individual functional Area IS Still in Existence)

INPUTS

Marketing

Marketing IS

Accounting

Accounting IS

Sales

Sales IS

Finance

Finance IS

Service

Service IS

Production

Production IS

Information System

OUTPUTS



• The emphasis Corresponds to the idea of a system as a business• A business operates within a constantly changing system• A business has various actors who impact it (Customers, Suppliers,

Competitors, Government)• A business has various inputs (Raw Materials, Services, Equipment)

• A business Transforms goods (WIP, Value-Added Services)

• A business has various Outputs (Products, Services)

• A business operates in a synergistic manner

• The Change in System Processing reflects the trend in Business Process Redesign (BPR)• The emphasis is in not merely improving on the existing system, but in re-

inventing the manner in inputs are processed


Modeling Diagram Conventions• Structured Methodology Goals

• Used for requirements specification, systems analysis and systems design

• Intended to structure a project into small, well-defined activities • Specifies the sequence and interaction of these activities • Use diagrammatic and other modeling techniques • Give a precise (structured) definition • Are understandable by both users (clients) and developers

• Structured Methodology (Intended) Advantages• Reduce life cycle development costs through improved analysis and design • Improve quality of systems delivered • Improve project management, planning and control • More effective use of inexperienced staff • Improve communication

• Self documenting

• User Analyst• Designer Analyst• Designer User


Modeling Diagram Conventions• Available Methodologies

• Gane & Sarson (Chris Gane and Trish Sarson): Late 1970s• Yourdan: Late 1970s• Demarco: Late 1970s• Merise (France): late 1970s

• Information Engineering (Finkelstein and Martin): Late 1970s/early 1980s • Structured Systems Analysis and Design Method (SSADM): - 1980

??? Which one will we Use ???• Gane & Sarson

??? Why ???

• It is (perhaps) still the most common

??? Are there Differences ???

• Some, but basically trivial:

Process Representation:Process Name

Gane & Sarson

Process Name

Demarco/Yourdan SSADM

Process Name


Modeling Diagram Conventions

Rectangle

• Basic Symbols

Source OR Destination of Information

Customer C.E.OSupplier

• Sometimes, for the sake of clarity, an Information source/destination is duplicated

?Customer

SupplierCustomer

• In that case, a duplication symbol is associated with the source/destination

?Customer

SupplierCustomer

• If the source/destination appears more than once, a multiple duplication symbol is used

?Customer

Supplier Customer

Customer

A

BB

B

• Note also that Identifying notation may also be used


Modeling Diagram Conventions• Basic Symbols

A Process/Activity which transforms/adds to data

• Processes are generally not duplicated, but can contain identifying notation

Rounded Rectangle Marketing IS Update

InventoryVerify that an Order is valid

Compute Monthly

Sales

35

IDS

Compute Monthly

Sales

4.2

C:/CMS.exe

Process Number Hierarchy/Activity Number

Department Program Name

Function/ Process/ Activity

Description

Identification

Physical Location



A data store

• Data stores are generally annotated with a number and descriptive name

Open-ended Rectangle Database File Temp. Storage

Accounts ReceivableD1

CustomerD2

EmployeeD3

InventoryD4

• As with processes, if data stores are duplicated in a diagram, extra lines are added

?Supplier

CustomerD2

CustomerD2

CustomerD2

• Here, the store has 3 lines at the left to indicate it appears 3 times in the diagram



A data flow: Information of any sort (written or oral), Invoices, Receipts, Database data, etc.

• The direction of the arrow shows the direction of the flow

• Data flows are ALWAYS assigned names:

?

• Unless it is completely obvious:

Customer CustomerD2

The process receives a payment from a Customer

After Processing, the Customer Database is updated

?Customer CustomerD2Customer Payment Updated Cust. Data

• Data flow names should be unique (unless the same data flow is generated at multiple locations)

Produce Paycheck

Employee(Paycheck)



A data flow: Information of any sort (written or oral), Invoices, Receipts, Database data, etc.

• If data flows in both directions, separate arrows should be used (Don’t use )

• Sometimes, data flows can become unwieldy:

?

• In which case we might want to merge data flows

CustomerD2

?

Customer Data ? CustomerD2

Customer Data

Updated Customer

Data

Customer

Customer Order

Customer Payment

Customer Return

Customer Complaint

CustomerCustomer

Transactions?


• Analysis/design is still (essentially) a top-down approach

Modeling Diagrams• General Principles

• When we need to, we can ‘explode’ processes

Marketing IS

• Analogous to our previous ‘Forest vs. Tree’ Idea

Marketing IS

~~~

~~~

~~~~

~~~~~~~

~~~~~~~

~~~~

~~~

~~~

• We can continue until there is nothing left to ‘Explode’


Modeling Diagrams• Context Diagrams

• Identifies the system boundaries and responsibilities.• Determines the boundaries, actors and interactions required.• Identifies Primary Data Flows

Harpo’s Book Club Members

Potential Subscribers

Suppliers

Customer Order

Invoice

Shipped Product List

Payments

Club Promotion

Subscription Order

Title Announcements

Purchase Orders

Product Invoices

Payments

Publishers

PaymentsInvoicesAdvertising

Agreements


• Intended to show all sub-processes and tasks and which can be ‘exploded’

Information System

Marketing Systems

Production Systems

Accounting Systems

Finance Systems

Process Control System

Inventory System

Inventory Receipt System

Inventory Ordering System

Modeling Diagrams• Decomposition Diagrams

Decomposition Diagrams(Hierarchy Chart)


Modeling Diagrams• Data Flow Diagrams (DFDs)

• Exploded Context Diagrams• Shows all Processes, sources/destinations of data, data stores, and data flows• Intended to be top-down

CustomerCustomer

Order

Verify Order

Pending OrderD3

Valid

Order

Process

Order

CustomerD1

Credit Status

BooksD2

Book Details

Gather Publisher

Requisition

PublisherD2

Publisher Address

Publisher

Purchase Order



• Basic DFD Guidelines

1. Identify External Entities involved

2. For Each Entity, Identify scheduled inputs and Outputs

• Data Flows are Not Physical ProductsNote:

3. For each Entity Input and Output, determine which process the receives the entity outputs and which process will generate the entity inputs

• Book Invoices are shipped, not the Books themselves

?

4. For Each Process, Identify what data stores need to be accessed for inputs and which data stores will be updated or given new outputs

?




• Data Flows MUST ALWAYS flow to or from a ProcessNote:

? ??




• Processes MUST ALWAYS have inputs AND OutputsNote:

? ?

Generate Employee Banking

Statement

A Black Hole A Miracle

• The inputs to a process must be sufficient to produce the output

Where did the Accounting Information Come From ??

Employee Data

EmployeeEmployee

Address

Bank

Statement

A Grey Hole



Verify Order

1.1

Assemble Publisher

Requisition

1.2

Verify Shipment

1.3

Assemble Customer

Order

1.5

Assign Shipment

1.4

Process Order

1.0

• Exploding DFDs

• Processes should be exploded according to the Decomposition Chart

1.0: Process Order

• Notice that at this point in time, all we are doing is listing the activities Involved

• We should, however, be able to determine (approximately) the order of processing, and assign identifiers accordingling



• Exploding DFDs

• Of Course, we will have to add details

Customer

Verify Order

1.1

Pending OrderD3

Valid

Order

Process Order

Publisher

PublisherD4Publisher

Address

Publisher OrdersD5

PO Details

Purchase Order

Publishers Consign.

NoteTitle

Quant.

Order

Details

Customer Order

Customer

Data

Ship.

Note

Title Orders

Order Details

Assemble Publisher

Requisition

1.2

Verify Shipment

1.3

Assemble Customer

Order

1.5

Assign Shipment

1.4

1.0: Process Order

BooksD2 Book Details

CustomerD1

Credit Status



• Exploding DFDs

• We can now continue Exploding

Publisher

Copy of PO

Order Date, PO#

Assemble Publisher

Requisition

1.2.4.

Copies Total Number of

Copies

1.2.3.

Note Order Info. In Pending Orders

1.2.6. 1.2.5

Create PO in Progress Record

1.2: Assemble Publisher Requisition

PublisherD4

Pending OrderD3

Publisher Ordering Information

Pending Order Details

Retrieve Pub. Order

Info.

1.2.1.

Extract Publisher

Orders

1.2.2

Totals by

Title

Unit

Orders

Publisher Address

Business Terms

P.O

Publisher OrdersD3P.O

Details

Order Details



• Exploding DFDs

??? When Do We Stop ???

When We are done


Documents

MIT5312: Professor KirsModeling Tools Slide 1 Modeling Tools