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System modelling
System modelling helps the analyst to
understand the functionality of the
system and models are used to
communicate with customers
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What is a model?
Model – a pictorial representation of
reality.
– Just as a picture is worth a thousand
words, most models are pictorial
representations of reality.
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Models: Logical and Physical
Logical model – a non technical pictorial representation that depicts what a system is or does. Synonyms with essential model, conceptual model, and business model. Physical model – a technical pictorial representation that depicts what a system is or does and how the system is implemented. Synonyms are implementation model and technical model.
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Why Logical System Models
Logical models remove biases that are
the result of the way the system is
currently implemented, or the way that
any one person thinks the system
might be implemented.
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Why Logical System Models….
Logical models reduce the risk of missing
business requirements because we are too
preoccupied with technical results.
Logical models allow us to communicate
with end-users in non technical or less
technical languages.
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Process modeling – a technique used
to organize and document a system’s
processes.
– Flow of data through processes
– Logic
– Policies
– Procedures
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Data flow diagram (DFD) – a process model
used to depict the flow of data through a
system and the work or processing performed
by the system. Synonyms are bubble chart,
transformation graph, and process model.
DFDs have become a popular tool for
business process redesign.
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Process Concepts
Process – work performed by a
system in response to incoming data
flows or conditions. A synonym is
transform.
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Decomposition Diagrams
Decomposition diagram – a tool
used to depict the decomposition
of a system. Also called hierarchy
chart.
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Process Logic
Decomposition diagrams and data
flow diagrams are effective tools for
identifying processes, but are not
good at showing the logic inside those
processes.
– Eventually need to specify detailed
instructions.
17
Process Logic…..
– Should effectively communicate
with both users and programmers.
– Flowcharts and pseudo code are
difficult for users to understand.
– Structured English has advantages
over natural English with some of
the rigor of programming logic.18
Modeling Logic With Structured English
Stuctured English is a modified form of
English used to specify the logic of
information system processes. Although
there is no single standard, structured
English typically relies on action verbs
and noun phrases and contains no
adjectives or adverbs.19
Problems with Natural English
Many of us do not write well, and we
also tend not to question our writing
abilities.
Many of us are too educated to
communicate with an audience that
may not have had the same
educational opportunities.
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Some of us write everything like it was
a program. If business procedures
required such precision, we’d write
everything in a programming language.
Too often, we allow the jargon and
acronyms of computing to dominate our
language.
Problems with Natural English ….
22
English statements frequently have an excessive or confusing scope.
We overuse compound sentences Too many words have multiple definitions. Too many statements use imprecise adjectives. Conditional instructions can be imprecise. Compound conditions tend to show up in
natural English.
Problems with Natural English.…
23
Modeling Logic With Decision Tables
Structured English can become more difficult to understand and verify as logic becomes more complicated. A diagram becomes more clearer. A decision table is a diagram of process logic where logic is reasonably complicated. All the possible choices and the conditions are represented in tabular form. 24
Modeling Logic With Decision Trees
A decision tree is a graphical technique that depicts a decision or choice situation as a connected series of nodes and branches. The decision tree used here is not a management science decision tree where one chooses the best among alternatives. This one is without probabilities and is used to diagram the same sort of situations for which decision tables were used. 26
Both decision tables and decision trees are used as communication tools designed to make it easier for analysts to communicate with users. How to decide whether to use Flowcharts, Structured English, Decision Tables or Decision Trees when modeling process logic depends on whichever method you prefer and understand best. But mostly it depends on task you are performing. 28
The assessment is based on an outline
design of system requirements in terms
of Input, Processes, Output, Fields,
Programs, and Procedures. This can be
quantified in terms of volumes of data,
trends, frequency of updating, etc. in
order to estimate whether the new
system will perform adequately or not.
This means that feasibility is a study
based on outline. 30
Feasibility analysis is the process by which feasibility is measured. – Feasibility should be measured
throughout the life cycle. – The scope and complexity of an
apparently feasible project can change after the initial problems and opportunities are fully analyzed or after the system has been designed.
– Thus, a project that is feasible at one point in time may become infeasible at a later point in time.
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Feasibility Assessment Why feasibility assessment?
– Information systems are major investments
– IS projects are subject to the same cost justifications as any other capital investments
– Business value paradox (hard to explain)
– Avoid "black hole" projects 32
Feasibility Checkpoints During Analysis
– Systems Analysis -Survey Phase
• ``Do the problems (or opportunities) warrant the cost of a detailed study of the current system?''
– Systems Analysis - Study/Definition Phase
• Better estimates of development costs and the benefits to be obtained from a new system. 33
Feasibility Checkpoints …
• Requirements often prove to be more extensive than originally stated.
• If feasibility is in question, scope, schedule, and costs must be rejustified.
– Systems Analysis - Selection Phase
• A major feasibility analysis evaluating options for the target systems design. 34
Feasibility Checkpoints …– Typical options that are evaluated include
• Do nothing! Leave the current system alone.
• Reengineer the (manual) business processes, not the computer-based processes.
• Enhance existing computer processes.
• Purchase a packaged application.
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• Operational Feasibility
• Technical Feasibility
• Schedule Feasibility
• Economic Feasibility
Tests of Feasibility
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• Operational Feasibility How well will the solution work in the organization?
• Technical Feasibility How practical is the technical solution?How available are technical resources and expertise?
Tests of Feasibility….
37
• Schedule Feasibility How reasonable is the project timetable?
• Economic Feasibility How cost-effective is the project or solution?Cost-benefit analysis
Tests of Feasibility…..
38
• Questions to Ask Is the problem worth solving? Will the solution to the problem
work? How do end users and
management feel about the solution?
What might end-users and management resist in the new system? Can it be overcome?
Operational Feasibility
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Has a usability analysis been
conducted? How will the working environment of
users change?
Operational feasibility defines the
urgency of the problem and the
acceptability of the solution. It should
answer the following question: If the
system is developed, will it be used?
Operational Feasibility….
40
Operational Feasibility….
Included here are:
Manpower problems
Management resistance
Organizational conflicts
Legal aspects
Government regulations41
Operational Feasibility….
It evaluates whether the system
can work or will work. A
workable solution might fail
because of end-user or
management resistance.
42
Using Pieces Frame Work
Performance- the system should provide
adequate throughput and response time
Information- the system should provide
end users with timely, pertinent, accurate
and useful information.
Economy- system should offer adequate
services at reduced cost.
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Using Pieces Frame Work...
Control-the system should have
adequate controls to ensure
confidentiality, integrity and availability
Efficiency- make optimum use of the
resources available.
Services- the system should be reliable,
flexible and expandable.
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• Questions to Ask Is the proposed solution
practical? Do we possess the necessary
technology? Do we possess the necessary
technical expertise? Is the technology mature enough
to be applied to the problem? If technology is not available, can
it be acquired?
Technical Feasibility
45
Technical Feasibility….
Some people prefer state-of-art
technology, but most firms prefer to
use proven technology because of
large customer base for obtaining
advice concerning problems and
continuous improvement.
46
Schedule FeasibilityTechnology could be available but not expertise, learning new technology can impact on the schedule.
Are projects deadlines reasonableAre deadlines mandatory or desirableHow far can the deadlines be extendedWhat are the cost associated with such
extensions in deadlines.
Missed schedules are bad, but inadequate systems are worse. 47
Many projects are economically
feasible, the question to ask here is:
Are the possible benefits of solving
the problem worthwhile?
Economic feasibility is a measure of
the cost-effectiveness of a project or
solution
Economic Feasibility
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Economic Feasibility…
Cost-benefit analyses
How much will the system cost?Development costsOperation costsMaintenance and support costs
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•Benefit analyses Tangible benefits can be easily
quantified. Measured in terms of monthly or
annual savings, or of profit to
organization Intangible benefits more difficult
to quantify.
Benefit Analysis
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Benefit Analysis
Tangible Benefits Fewer processing errors Increased throughput Decreased response time Elimination of job steps Increased sales Reduced credit losses Reduced expenses Opening of new markets Improvement of
Management and planning
Intangible Benefits Improved customer
goodwill Improved employee
morale Better service to
community Better decision-making Improved asset
utilization Improved resource
control
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Economic Feasibility
Payback analysis– How long will it take to recoup the costs of
this project?
Return on investment (ROI) analysisEstimated lifetime benefits - estimated
lifetime costEstimated lifetime cost
Net present value analysis (translates the future income to the present value)
52
Feasibility Analysis
Compare candidate systems on basis of several characteristics
– Better analysts always consider multiple solutions
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Legal and Contractual FeasibilityThe process of assessing potential legal and
contractual ramifications due to the construction of a system e.g.
CopyrightLabor lawsForeign trade legislationFinancial reporting standardsOwnership of softwareLicense agreement for software and hardware
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Market and Real Estate FeasibilityMarket Feasibility Study typically involves testing geographic locations for a real estate development project, and usually involves parcels of real estate land. Developers often conduct market studies to determine the best location within a jurisdiction, and to test alternative land uses for a given parcels.
Market Feasibility takes into account the importance of the business in the selected area.
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Resource Feasibility
This involves questions such as how
much time is available to build the new
system, when it can be built, whether it
interferes with normal business
operations, type and amount of resources
required, dependencies, etc. Contingency
and mitigation plans should also be stated
here.56
Cultural FeasibilityIn this stage, the project's alternatives are evaluated for their impact on the local and general culture. For example, environmental factors need to be considered and these factors are to be well known. For example, religion, language, believes, signs and symbols, mannerism, timeliness.
Further an enterprise's own culture can clash with the results of the project. People could have been benefiting from inefficiencies.
57
Political Feasibility
The process of evaluating how key
stakeholders within the organization view
the proposed system e.g.
New system may affect distribution of
power
Stake holders may take steps to block,
disrupt or change the intended focus of the
system58