Models

Kieran Mathieson

Outline

What Are Models? What Are Models For? Process Models Data Models Decision Models

What Are Models?

Representation of something Not as complex as the real thing

Omits details

Different types of models for different tasks

Accurate models are a critical IT resource

Example

http://www.flexsim.com

Example

http://www.flexsim.com

Example

Example

Start

Take order

Check orderwith customer

Get paymentinformation

Get shippinginformation

Check shippinginformation

with customer

Check paymentinformation with

customer

Creditauthorized?

Refer customerto manager

Ordercomplete

YesNo

Example

Example

Department Employee

TeamSkills

ProjectProductCustomer

manages

employs

manages

in

has

deliversbuys

has

http://db.grussell.org/section021.html#_Toc67114582

What Are Models For?

Understand Figure out how something works

Communicate Show others how it works

Improve Can't improve something you don't understand

Predict What will happen if we …

Automate Replace parts with IT

Outline

What Are Models? What Are Models For? Process Models Data Models Decision Models

Process Models

Most process models represent activities

Wake

Hungover?

Go to class

Study

Lunch

Hungover?

Dinner

Bed

Yes

Yes

No

No

Process Models

Some models represent other aspects of processes than activities

http://www.cs.utoronto.ca/~eric/ieeeexp/ieeeexp2.html

Process Model Issues

How much detail? How do you organize complexity? How concrete?

If Jim does a task, do you put a symbol for Jim on the diagram, or just represent the task?

How do you maintain process models?

Outline

What Are Models? What Are Models For? Process Models Data Models Decision Models

Data Models

Represents the data needed to support processes

Drives database implementation Errors in process models lead to errors in

data models lead to errors in database implementation lead to errors in applications lead to long weekends at work

Entity Relationship Model

Department Employee

TeamSkills

ProjectProductCustomer

manages

employs

manages

in

has

deliversbuys

has

http://db.grussell.org/section021.html#_Toc67114582

UML Class Model

Outline

What Are Models? What Are Models For? Process Models Data Models Decision Models

Decision Models

Mathematical representation of a situation Simulations models

Build software that more-or-less directly mimics the situation

Software elements act like real elements

Optimization models Use a well-known mathematical technique to

find the best answer to a problem

Simulation Model

SimCity 4

Optimization Model

You have a supply depot on a river You want to install a security fence You have 1,000 feet of left-over fencing What’s the most space you can enclose?

Jetty

Buildings

Optimization Model (cont.)

A = W ( 1000 – 2 W ) A = 2W2 – 1000 W dA / dW = 4W – 1000 dA / dW = 0 when W = 250

Jetty

BuildingsW

1,000 – 2W

Outline

What Are Models? What Are Models For? Process Models Data Models Decision Models

There are lots of models in IS. Accurate models are a critical

resource.