Staffordshire
UNIVERSITY
School
of
Computing
Systems Development
Methodologies
Dr. Andy Seddon
Content
Staffordshire
UNIVERSITY
School
of
Computing
1.
2.
3.
4.
What are methodologies for systems
development?
Advantages and disadvantages of
methodologies
Physical and logical approaches
Comparison of types of methodologies
(separate lecture slides)
Dr. Andy Seddon
Staffordshire
UNIVERSITY
School
of
Computing
1. Systems development
methodologies
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a collection of procedures, techniques, tools and
documentation aids which will help systems
developers in their efforts to implement a new IS
consist of phases and sub-phases to assist
planning, management and control of projects
techniques are ways of refining a given activity
in a system development process, each technique
may involve using one or more tools
Dr. Andy Seddon
2.1 Advantages of methodologies
Staffordshire
UNIVERSITY
School
of
Computing
they produce better ISs
 they provide a better development
process
 they use standard methods to produce
systems that are easier to maintain and
improve
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Dr. Andy Seddon
Staffordshire
UNIVERSITY
School
of
Computing
2.2 Disadvantages of
methodologies
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some have too little scope
some are not properly thought out
some do not consider the work or social context of the
system
methodologies do not guarantee success
some are only tailored to large, complex organisations
better at designing transaction processing systems than
MIS?
prototyping and 4GLs do not always fit neatly with formal
methodologies
Dr. Andy Seddon
3.1 The logical approach
Staffordshire
UNIVERSITY
School
of
Computing
the logical design is carried out first
 it is the paper based system
 it defines what the system is supposed
to do and the data items it deals with
 concerned with the what, rather than
the how

Dr. Andy Seddon
3.2 The physical approach
Staffordshire
UNIVERSITY
School
of
Computing
the physical design is carried out last
 it is the actual computer system which
will support the logical design
 concerned with the how, rather than the
what

Dr. Andy Seddon
4.1 Types of methodology
Staffordshire
UNIVERSITY
School
of
Computing
Process driven methodologies
 Data driven methodologies
 User driven methodologies
 Hybrid methodologies - SSADM
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Dr. Andy Seddon
4.1.1 Process driven
Staffordshire
UNIVERSITY
School
of
Computing
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The systems development lifecycle (SDL) can be
viewed as process driven
concentrates on how data is processed
structured analysis breaks the process down into
phases and stages
most structured analysis and design methodologies
are process driven
aids analysis of manual processes
appropriate where small databases are required
examples - Yourdon, STRADIS
Dr. Andy Seddon
4.1.2 Data driven
Staffordshire
UNIVERSITY
School
of
Computing
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concentrates on the data processed
data analysis is more suitable for database design
these techniques are more appropriate for large
projects
example - Information Engineering
data needs are identified before processing options
Dr. Andy Seddon
4.1.3 User driven
Staffordshire
UNIVERSITY
School
of
Computing
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Soft Systems Methodology - people oriented
approach
SSM is a way of analysing the ‘problem
situation’ in open systems (organisations)
a way of tackling unstructured and poorly
defined problems in the real world
may produce more effective system but less
efficient in terms of data handling
example - Checkland’s SSM
Dr. Andy Seddon
4.1.4 Process versus data driven
Staffordshire
UNIVERSITY
School
of
Computing
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a company manually analyses overdue payments
according to the number of days the debt is
outstanding (0-30, 31-60, 61-90, 91+)
– process driven analysis would automate the
classification process with no information being
left ‘on file’
– data driven analysis would store the input data so
it could be used for a number of potential uses
which of the above approaches would be most
suitable and why?
Dr. Andy Seddon
Staffordshire
UNIVERSITY
School
of
Computing
Data or the type of data used is
unlikely to change BUT the uses
to which it will be put, on the
other hand, are likely to alter.
Dr. Andy Seddon