System Analysys207 Cls4

7/31/2019 System Analysys207 Cls4

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PowerPoint Presentation for IS-207Copyright 2006 Michael W. Schaffer. All rights reserved.

Slide 1

Systems Analysis & Design

Class #4 - Requirements6/11/2012 11:46:55 PM


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Slide 2

PDP: Requirements

What does it do? and For

whom does it do it?

Who: Product Manager, Tech Lead, QALead, Project Manager, plus

Define what the system does, and for

whom. Develop cost assessment and

baseline schedule, bottom-up

Address risks early: prototype to test

feasibility and platform/tools as needed.

Discovery

Requirements

Specifications

Development

Integration

Launch Maintenance

AlphaBeta


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Slide 3

Who drives Requirements?

Product Manager is responsible forWhat is to-be-built

Functional and non-functional req.s

Maintain a clear understanding ofexternal forces and customer needsfact-based.

Business AnalystsTechnology staff involved early toprovide feasibility and balance


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Slide 4

Requirementsaka Needs?

A Team Dialog

A taxonomy of requirements

Users & Use Cases, UI/UEData flow analysis

Process analysis & documentation

Revised Schedule and Plan


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Slide 5

Requirements Taxonomy

Product Functionality

Non-Functional

Platform & Compatibility (O/S, DBMS)Bandwidth & connectivity, Performance

Marketing and Sales

Channels, Pricing and Licensing

Packaging: SDK, integration hooks

Product Support & Training, Roll-out


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Slide 6

IBM Sales Modelc. 1986

Deep and broad research(interviews and analysis)

Document Information Needs,and develop benefit models

Build a Conceptual Model

specificdata-flows to consumersof information.

Pitch the solution.


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Slide 7

Textbook challenge #1

The text differentiates betweenBusiness ProcessAutomation, BPImprovement, and BP Re-engineering.

Improvement

any incremental systems projectInventiona 1.0 project


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Slide 8

Know the history, then break it

All projects benefit from knowing

the background, whether

incremental or true 1.0.Get the background.

All projects benefit from trying to

expand the solution space early.More users, more information flows


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Slide 9

Who is the end-user?

Develop a clear vision of who

uses the system:

Information NeedsExisting solutions (all types) and theirissues with the status quo

Goals & Fears their uniqueperspective on the system


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Slide 10

Political Support

The process of requirements

gathering (through end-user

interviews, observation, etc.)creates opportunity to build

critical support for your project.


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Slide 11

Other players (stakeholders)

Buyer is rarely the end-user

Influencers: IT, other departments

In Venture-backed start-ups, theinvestors are critical.

Your Boss


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Slide 12

Joint Application Development

JAD sessionslarge, cross-

functional meeting to discuss the

proposed systemExpensive -- lots of people

Subject to domination

Use with care, with greatfacilitators only.


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Slide 13

Persona

A useful technique for

documenting in-depth studies

of end-usersThe Inmates Are Running the

Asylum : Why High Tech Products

Drive Us Crazy (Alan Cooper)


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Slide 14

PersonaII

Especially useful when system to

be developed is 1.0: no old

models, no existing basisEnd-users are novices, or new tothe proposed system

Requirements are difficult to defineMultiple groups of end-users


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Slide 15

PersonaIII

Your end-users will determine the

style, look & feel, flavor of your

system and its interfacesUser Experience = Interactive Brand

Iconography, Typography, Palette

Visual Design has impactDevelop interactive requirements


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Slide 16

The System is the Data

At the core: any system is

defined by the data obtained,

stored, and displayedData flow analysis is the

center/core/key


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Slide 17

DFDPractical Example

Launched Dec. 11, 1998, the Climate Orbiter plunged too steeplyinto the Martian atmosphere Sept. 23, 1999, and either burned upor crashed. In an initial failure report released Oct. 15, 2000, thereview board blamed the navigation error on a communicationsfoul-up between NASA's Jet Propulsion Laboratory and prime

contractor Lockheed Martin.

Collect,analyze,

generate flightcontrol data

JPL-1

J1 JPL store

Convert datafrom Metric to

English

?

LM1 LM store

Controlspaceflight

LM-1

English data

Transfer of Flight Control DataThis processwas missing

Metric data

Transfer data

?

Who wasresponsible

for this task?


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Slide 18

Context Diagram

Shows the context into which thesystem fits

Shows the overall business process asjust one process

Shows all the outside entities thatreceive information from orcontribute information to the system


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Slide 19

Context Diagram of Alibris

UsedBook

Sellers

BibliographicSources

of Catalog Data

WWW Customers

Sales Channels(BN.com, Borders, Amazon,eBay, Chapters, Ingram,)

AlibrisSystems

New BookPublishers

and Distributors

LibraryCustomers


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Slide 20

Context of Quicken1995 (?)

QuickenUser

QuickenOn PC/Mac


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Slide 21

Quicken - 2006

QuickenUser

QuickenOn PC/Mac

Banks

VISA/MC

BrokerageVendors

(check writing)


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Slide 22

Data Flow Diagrams

Keep them simple: Gane-Sarson

Only three elements:

Interface / ExternalsProcess

Data Store

And data flows to inter-connect


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Slide 23

DFD Shapes from Visio

From Flow Chart /Data Flow Diagram

Process

Data Store

External Entity

From Software Diagram /Gane-Sarson DFD

Process

ID #

ID#

ExternalEntity

Data Store1

External

Entity

Data Store

Process

From Flow Chart /

Data Flow Diagram

Visio 5.x Visio 2000


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Slide 24

External Interfaces

The Text says External Entities:

Visio calls them Interfaces.

An API or an external source, oran external consumer of data.

Partner organizations get their

specs, and someone competent.A lot harder than it should be


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Slide 25

Data Stores

Sure, could be a database ... but

do not get caught up in specifics

too early.(Flat) Text files, XML files, cookies

firmware any sort of

repository.Physical model comes later!


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Slide 26

An informal DFD

Inventory Files2,000,000

updates / day

8,000Sellers Online

Inventory Tools&

Pricing Service

For-sale

Inventory

with Works

BibliographicSources

Catalog

WorksCreation

1M ActiveWWW Customers

WebSite

Interfaces

Inventory Processingand

Works Matching

B2B Partners

Finance

SystemOrders

Purchase OrdersVouchersInvoices

Debit/Credit MemosGeneral Ledger

A/R & A/P

EDITranslators,B2B Systems

ANSI X.12and

Flat files

Customer & OrderInformation

CustomerEmails

Inventory Replicationto Partners

andReal-time API's


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Slide 27

DFDA more formal example

Alibris, a typical eCommerce

company

DFD starts basic and cleanExplode to more detail as needed.


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Slide 28

Data Flow: Keys and Payload

Data flows start general, i.e. ordersor inventory.

As you drive deeper, identify theprimary keys in each element of thedata flow:

i.e.: Order number, SKU number

Think about uniqueness is the process

feasible with the data present?


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Slide 29

Data Flow: Keys and Payload

Do not get caught-up in

specifying every single data

element of the payload.Use next phase for details

Map the flow of keys, esp. across

system seams to validate thedesign.


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Slide 30

Data Flow: Keys example

Partner sends an order for a setof books

Purchase Order Number, SKUs

Acknowledge Purchase OrderOrder number, mapped to PO

Line-item IDs needed?Ship product

Ship status by PO? Line-item?


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Slide 31

Elements of a Use Case

Trigger -- event that causes thescenario to begin

External trigger

Temporal trigger

All possible inputs and outputs

Individual stepsShow sequential order

Show conditional steps


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Slide 32

Scenario Template (Use Case)Scenario Description

Scenario Name: ID Number:_ __

Short Description:

Trigger: _______________________________________________________________

Type: External / Temporal

Major Inputs:

Description Source

________________________ ___________

________________________ ___________

________________________ ___________

________________________ ___________

________________________ ___________

________________________ ___________

Major Outputs:

Description Destination

_______________________ ____________

_______________________ ____________

_______________________ ___________________________________ ____________

_______________________ ____________

Major Steps Performed Information for Steps

This template can be downloaded from the course download page.
http://www.sims.berkeley.edu/courses/is207/s05/downloads-2005.htmlhttp://www.sims.berkeley.edu/courses/is207/s05/downloads-2005.html


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Slide 33

Integrating Scenario

Descriptions

DFDs generally integrate scenariodescriptions

Names of use cases becomeprocesses

Names of inputs and outputsbecome data flows

Combining small data inputs andoutputs into a single flow


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Slide 34

Steps in Building DFDs

Build the context diagram

Create DFD fragments for each

scenarioOrganize DFD fragments intolevel 0

Decompose level 0 DFDs asneeded

Validate DFDs with user


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Slide 35

DFDCommon Errors

Miracle

Black HoleGray Hole


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Slide 36

DFDPacket Concept

Pay phone

bill

1

Telephone Service

ProviderItemized calls

& invoice

Itemized calls

Invoice

Incorrect use

of the packet

concept

Correct use

of the packet

concept


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Slide 37

Illegal Data Flows


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Slide 38

Use cases do not collect formulae, state,

cardinality, performance, uptime, ...

Examples:

1. Order cost = order item costs * 1.06 tax

2. Promotions may not run longer than 6 months.

3. Customers only become Preferred after ...4. A customer has one and only one sales contact.

5. Response time is ...

6. Uptime requirement is ...

7. Number of simultaneous users will be ...

Capture those in any form available


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Slide 39

Other semantics

A system is a collection of processes(Verbs) operating on data entities(Nouns).

As you collect requirements, thinkabout the nouns you encounter asentities.

When you encapsulate behavior anddata, this becomes an object.


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Slide 40

Non-Functional Requirements

Gathered from users, andenvironment.

Hardware, Operating system,Network issues

Marketing requirements from saleschannel (how to sell it?)

Operating requirements Performance requirements


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Slide 41

What happened to Prototypes?

Do your users understand the

system?

Build a UI shell that shows theinformation interfaces and reports

Iterate with the users until clarity is

achieved.Document the results.


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Now revise the Plan

All this design enables the team

to revisit the implementation plan

How might this be built?Components available to buy?

Resources needed?

Feasible?

Create a detailed project plan.

Documents

System Analysys207 Cls4