Information Technology IMS5024 Information Systems Modelling Lecture 1 Modelling and ISD.

Information Technology

IMS5024 Information Systems ModellingLecture 1

Modelling and ISD

School of Information Management & Systems

1.2

Contents

• Welcome, Introductions and housekeeping

• Approach

• What is Modelling?


1.3

Lecturers

Unit-Coordinator• Andrew Barnden• Building S, 7-14• Phone: 99032469• E-mail:

[email protected]

• Dr Helana Scheepers• Building S, 4-10• Phone: 99031066• E-mail:

[email protected]


1.4

Unit outline

• Unit home page

http://www.sims.monash.edu.au/subjects/IMS5024• Objectives• Assessment• Pass requirements• the astute student


1.5

Pass requirements

• 50% or more of the total available marks

in addition, these conditions apply• minimum 40% of the examination marks

AND• minimum 40% of the assignment marks


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The Astute Student will:

• attend every lecture and every tutorial• read the reference material before lectures and

tutorials• listen to what the lecturers say• NOT memorise the overhead slides, but instead,

investigate and form opinions about the slide topics

• ask questions


1.7

Assessment

• Modelling research report • Synopsis for evaluation in week 3

• Due Week 6

• Object oriented modelling assignment• Due Week 11

• Exam


1.8

Pitfalls

• Read website regularly for updates on reading, class assignments and announcements

• Plagiarismhttp://www.sims.monash.edu.au/policies/plagiarism.html

• offenders will get caught


1.9

• Lecture 1:• Chapter 2 of Veryard, R (1992). Information Modelling:

Practical Guidance, Prentice Hall International, UK.• Lecture 2:

• Chapter 2 and 3 of Mathiassen, L and Dahlbom, B. (1993). Computers in Context: The philosophy and practice of systems design, Blackwell Publishers, UK.

• Chapter 2 of Hirschheim, R., Klein, H. and Lyytinen, K. (1995) Information Systems Development and Data Modelling: Conceptual and Philosophical Foundations, Cambridge University Press

Reading


1.10

Mathematical• an equation; (eg. E=mc2)

Symbolic/Visual• a theory; (eg. the theory of relativity)

• a hypothesis; (eg. the speed of light is not a limiting velocity)

• an analogy; (eg. a map)

Physical/Iconic• an artefact; (eg. a model car)

What is a model?


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1. Scaling Down; both in terms of size and complexity

2. Transfer Across; representation in relative position

3. Workability; in principle the model operates like the original as a consequence of 1&2

4. Appropriateness; to the aspect of reality under investigation

The nature of models


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The model is the reality

The model represents all of reality

The pathology of modelling


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Models are an agreed “language” by which a diverse group can communicate about an essential aspect of the “Universe of Discourse” (UoD)

It facilitates communication, and shared understanding, between people who have a different perspective about an aspect of reality in which they have mutual interest.

Why models are used


1.14

• A descriptive, narrative model - the big picture

• An aesthetic model - what will it look like

• An environmental model - where does it fit into the world

• A designer’s model - how does it fit together

• A fabricator’s model - what components are needed

• A builder’s model - what do we have to build it on

• A constructor’s model - how do we put it together

Models as a means of communication


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Client/user Analyst

Specs

Programmer

The problem of communication:views from the coalface


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Systems development is the process of modelling those aspects of the user’s physical requirements which can take advantage of the things a computer can do. The art of the analyst/designer is to convert what the users need to support their work into the form of instructions which a computer can follow

What is systems development?


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Data

Process

TaskDesign

Organisational Design

Objects

Events

The Discourse of ISD


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Strengths WeaknessesSimplify Omit detailRelate to a particular purposes Inaccurate (for some things)Relate to a specific audiences Incomprehensible (to some audiences)

No single model can accurately communicate information about ALL aspects of an information system.

Strengths & weaknesses of ALL forms of modelling


1.19

The analyst is interested in the “essential” model that depicts the essence of the system; what it must do independent of the technology or the actual system.

To achieve this the analyst engages in a process of abstraction, which also includes generalisation, to identify the logical equivalent of the physical world. When modelled, such logical equivalents are called logical or conceptual models.

The significance of conceptual models is that software can only represents such models and not the physical world.

The concept of the logical equivalence


1.20

• engineering systems are much easier to model than information systems

• what gets modelled is what gets built (and remember all models omit some detail!)

• some things are easier to model than others• some things are un-modellable• some models are un-buildable• systems development requires a large variety of

models to meet the needs of different audiences

Implications of systems modelling


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Using Models

The analyst needs to;• beware of simple modelling solutions (real

organisations are not simple)• think about the things which are too

complex and/or can't be modelled• beware of 'engineering' approaches to non-

engineering systems

Information Technology IMS5024 Information Systems Modelling Lecture 1 Modelling and ISD.

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