S556 SYSTEMS ANALYSIS & DESIGN

Week 6

Using Language to Focus Thought (cf., Wood, 1997)

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The language gives you a way to see: a framework for interpreting the things you

observe and a structure of understanding you can

elaborate as you learn more

Our Tool—Graphical Languages

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Advantages of a graphical language: a picture is worth a 1000 words

Our Tool—Graphical Languages

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A picture reveals relationship to the whole

A diagram supports systemic thought and makes it possible to create a coherent design response

Work Models

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Work models = a graphical language to capture knowledge about work

Models make concepts concrete, in order for the team to share and discuss ideas

Models can be used to communicate with clients

5 Work Models in Contextual Design

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Flow model The communication and coordination

Sequence model The detailed work steps to achieve a goal

Artifact model Physical things to support the work

Culture model Constraints on the work caused by policy,

culture, or values Physical model

Physical structure of the work environment

Flow Model (Beyer & Holtzblatt, 1998, p. 92, 93)

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The work must be broken into parts Different departments coordinate to get

its work done The flow model represents this

communication coordination necessary to make work happen

Flow Model (B&H, p. 92)

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U1(Secretary)

Worker

VendorMarketing manager- Produce proposal

checks

invoices

Request toschedule meetingw/ president

Bulletin board

announcement

Requires lotsof iterations

- Ensure bills paid on time

President

checks to sign

- Run the business -Meet w/ management

Request for clarification

Proposal to proof

- Invoice for services

Flow Model Rules (B&H, p.91)

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People and organization are bubbles on the model, annotated with their position & responsibilities

Flow is indicated as arrows between bubbles

Artifacts are shown in boxes on the line Informal communication and actions

are written without a box

Flow Model Rules (B&H, p.91)

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Places appear as large boxes, annotated with their responsibilities

Automated systems and databases usually should not go on the flow (they are shown as a large box with responsibilities only when they act like a physical place or an automated person)

Flow Model Rules (B&H, p.91)

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Communication breakdowns are shown with a lightning bolt

Note: the flow model needs to capture how work is really done

Specifying Processes

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Structured English is based on the logical constructs of:

sequence selection iteration

Sequence Model (see B&H

p.99)

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A sequence model represents: the steps by which work is done the triggers that start a set of steps The intents that are being accomplished The breakdowns that prohibit workers

from being efficient A sequence model supply the low-

level, step-by-step information on how work is actually done

Sequence Model

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A sequence model: Starts with the intent and trigger for the

sequence Lists each steps in order

Note: any steps that cause problems are labeled with a lightning bolt

Collecting Sequences During an Interview

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Steps (an action or thought preceding an action) The details of the tasks depend on the

scope of the group e.g., writing a memo (Department level vs.

task level vs. user-interface level) Get more details rather than less

Collecting Sequences During an Interview

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Hesitations & Errors When the users hesitates or makes errors,

ask Qs to find out what s/he is thinking about

This is an opportunity for your system to do better!

Hesitations for a thinking task could reveal decision points in the process

Collecting Sequences During an Interview

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Triggers (that cause the sequence of actions): may be discrete events, e.g.,??? may be based on time, e.g.,??? may be less tangible, e.g.,???

The system needs a way to tell the user there’s something to be done

Collecting Sequences During an Interview

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Every sequence has a primary intent (see B&H p. 98), which applies to the whole sequence

There will be secondary interests E.g., paying bills (primary intent), not

overdrawing her account (secondary intent)

Sequence Model: Example

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Intent: Hiring someone

Trigger: someone quits

Review her job

Define candidates’ qualifications & job descriptionIntent:Review the current position

Advertise the job opening

Receive applications

Review applicants

Check references of selected candidates

Intent: Eliminate unqualified candidates

Fewer candidates to invite on site

Sequence Model: Example

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Set up interview dates with selected candidates

Choose the best candidate

Making a job offer

Negotiate

Candidate accepts the job Candidate denies the offer

Choose the 2nd best candidate

Intent: make decisions about which candidate

UML: Activity Diagrams: Example

Customer Sales Stockroom

Request service

Take order

Fill orderPay

Deliver order

Collect order

http://www.uml-forum.com/tools.htm

DECISION TABLE

Specifying Processes

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Structured English is based on the logical constructs of:

sequence selection iteration

Limited Entry Decision Table

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When a customer wants to purchase an item, different conditions determine the actions you should take.

Limited Entry Decision Table

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First, identify the conditions: Under $50? Pays by check w/ 2 forms of ID? Uses credit card?

Next, identify the actions Ring up sale Call supervisor for approval Require a signature that matches one

on the back of the card

Limited Entry Decision Table

Under $50 Y Y N N

Pays by check w/ 2 forms of ID

Y N Y N

Uses credit card N Y N Y

Ring up sale X X

Call supervisor for approval X

Require a signature that matches one on the back of the card

X

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conditionsactions

General Rule

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Check the number of rules The number of answer: M (e.g., 2 for Y/N) The number of condition: N

M = M x M x M x M . . . (M to the nth power) E.g., 2 = 2 x 2 x 2 = 8rules

N

3

Mixed Entry Decision Table

Regular customer?

Y Y Y N N N

Order value $ 0-49

50-99

> 100

0-49

50-99

> 100

Free shipping X X

Discount given

0 10%

15% 0 5% 10%

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conditionsactions

Decision Tree: Hiring an Info Architect

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Collegedegree

Formal education in IA

Practicalexp in IA

Action

JobApplicant

yes

no

yes

no

yes

no

Job offer

Keep app

yes

no

Keep app

Reject

yes

no

yes

noyes

no

Keep app

Reject Reject

Reject

Exercise: Decision Tree/Table

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You are in a situation where going through job postings and deciding which jobs to apply for. Draw a decision tree or table with: three conditions three actions

Modeling

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What constitutes a good model?

Exercise: Flow Model

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Form 4 groups (5 people each) Develop a flow model based on the case

presented in Alter’s article