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SSM & Information Systems
Wilson’s approach to defining information requirements from conceptual models.
Why SSM for IS? How has it been applied?
SSM Overview
-
Finding out about the problem situation, including cultural/ political aspects
Choosing & building models of “relevant systems” of purposeful activity, each based on a world-
view
Taking action to improve ...
Debate the situation using the models (Comparison)
- Identify systemically desirable and culturally feasible changes
-Find accommodations between conflicting interests that will enable …
Understanding of the organisation,
including cultural and political
analysis
SSM for IS definition: based on Wilson’s approach
Find out about the problem situation
Root definitions
Conceptualmodels
Compare models with real world
Map toorganisation(role-roleflows)
Map activitiesto IPP’s
Defineinformationcategories
Defineactivity-activityflows
Todesign
(Adapted from Wilson, 1990)
FormCPTM
MalteseCross
Wilson’s approach - definitions CPTM - Consensus Primary Task Model. IPP = Information processing procedure
- a current information system, automated or manual.
Maltese Cross - matrix technique for comparing information requirements of CPTM with real world information provision (IPP’s).
Role - a position in the organisation. Roles are responsible for activities.
Consensus Primary Task Model (CPTM)
“What we are taking the organisation business processes to be.” (Wilson, 2001)
Still a Conceptual Model! “The consensus of the problem-
solving group that this is what they are taking the organisation unit to be doing (now or in the future).” (Wilson, 2001)
Various ways of producing this model.
Consensus models - comparing models
We can compare different (primary task) models based on different W’s.
One of these will be based on a neutral primary task description – something essential that no-one will dispute.
Consensus models - agreed activities
Take the neutral model’s activities
Examine other models’ activities
Add others after seeking agreement / accommodation
Choose activities that give a coherent model
Neutral model
100% consensus
Local consensus
Producing the CPTM
1 Produce initialCPTM from individualmodels
2 Derive RD from model
3 Derive test modelfrom RD
5 Modify RD and/or model(s)
4 Compare testmodel with tentativeconsensus modelConsensus PTM
Individualmodels
(CCTA, 1993)
Other ways of producing CPTM
Model the Mission Statement Already agreed Sometimes vague, seen as irrelevant, etc.
Extract it from a model of a wider system If you have one May be difficult to get a definable system from
the gaps Assemble it from smaller models
Within a general framework for organisations in system terms, into which they can fit – Wilson (2001) provides one
Consensus models - do we need them?
We now have an agreed model - a consensus primary task model
Often regarded as essential precursor to defining information requirements
Why?
CPTM takes W’s into account when forming the model.
Some analysts believe that the variety of viewpoints should be preserved in information definition by continuing with multiple models.
SSM for IS definition: based on Wilson’s approach
Find out about the problem situation
Root definitions
Conceptualmodels
Compare models with real world
Map toorganisation(role-roleflows)
Map activitiesto IPP’s
Defineinformationcategories
Defineactivity-activityflows
Todesign
(Adapted from Wilson, 1990)
FormCPTM
Information categories
“Information = data + meaning.” Information categories are therefore not
just data items, but are defined in a way that indicates how they’re used. E.g. “Stock availability” rather than
“quantity” Define the data in each category Lower level models tend to have more
detailed information categories.
Simple way to show information requirements
Re-order goods
Available products
Stock levels
Purchase orders3
What information does it require?
What information does it produce?
Input/output tableActivity Reorder goods Despatch
Order Receive delivery
Inputs Available products, Stock levels
Orders, Stock levels, Carrier availability
Delivery,
Outputs Purchase orders
Despatches Receipt, Rejection
Measures of performance
Stockouts Turnaround time
SSM for IS definition: based on Wilson’s approach
Find out about the problem situation
Root definitions
Conceptualmodels
Compare models with real world
Map toorganisation(role-roleflows)
Map activitiesto IPP’s
Defineinformationcategories
Defineactivity-activityflows
Todesign
(Adapted from Wilson, 1990)
FormCPTM
Maltese Cross
NW E
S
InputICs
OutputICs
IC1IC2IC3IC4IC5IC6 IC6IC5IC4IC3IC2IC1
Do...
Store...
Find...
Issue...
Activities from model
IPPs
Sales OP
Stock ctrl
Debtors
X
X
X
X
X
X
X
X
X X
XX
X X
X
X
Maltese Cross
InputICs
OutputICs
Data structures
Data structures
Current IPPs
Sales OP
Stock ctrl
Debtors
XX
X X
X
Stocklevels
Stock card - item no & qty
Orders
Order record
Item file -quantity available
X
Check order Despatch
goods
Stocklevels
Stock card - item no & qty
Item file -quantity available
Orders
Order record
N
S
E W
Organisational mapping What role is responsible for each activity?
1
842
3 5
7
6
?Marketingasst
MD
Sales Mgr
SalesMgr
Salesperson
Accountsclerk
Sales-person
Sales Mgr
Sales
Marketing
Accounts
Wilson’s approach – summary (for you to read)
Derive primary task model(s) and gain consensus about these. (“Consensus primary task model”)
Derive the categories of information (sets of “data + meaning”) needed to support the activities, and the information categories produced by activities. Enter the categories into both East and West sides of a Maltese Cross, representing output and input.
Create the NW and NE matrices, relating the categories to the activities which will use and create them.
Wilson’s approach - summary (2)
Take each existing Information Processing Procedure (IPP) and identify the information categories to which the input and output data belong. This gives the bottom half of the Maltese Cross.
Using the Maltese Cross, identify omissions, duplications etc. and define any necessary additional processes, avoiding duplication. (Wilson now does activity models of these new/changed IPP’s.)
Define management roles in terms of the activities for which each manager is decision-taker. Convert the “activity to activity” information flows into “role to role” information flows.
Rationale (1)
“Systems analysis aimed at information systems design, if it is to make much impact, must first concentrate on the activity system which the information system is to serve.” (Checkland, Systems Thinking, Systems Practice)
So, we conceptualise the activity (served) system before the information (serving) system.
Rationale (2) Data is not information. Information
involves attributing meaning, and can then inform action.
IS provide knowledge to support purposeful activities - hence people need to attribute meaning to the data, otherwise we just have a “data manipulation system”.
We need to understand what meaning people will give to data - hence useful to examine viewpoints, political factors etc.
Rationale (3) The activity system must contain activities
which are feasible and seen as meaningful, and form a consistent whole.
We need to understand the organisational situation & the environment - a “rich understanding” is provided by SSM
We need to agree what this consistent, feasible & meaningful activity system consists of - SSM gives us a way to do this.
Causes of IS failure•The wrong problem is addressed•Wider influences are neglected•Analysis is carried out incorrectly•Project undertaken for wrong reason•Users change their minds•External events change the environment•Implementation is not feasible•Poor project control
(See Bennett et al. section 2.3)
SSADM 4+ Business ModellingAn optional precursor to SSADM. Includes: Business Activity Modelling
Business Perspectives (why) Logical activity (what) Business events (when) Business Rules (how)
Work Practice Model User roles (who) Organisation structure & geography (where)
(See SSADM 4+ User Guide)
Business Activity Modelling Business Perspectives
What the business is trying to achieve “To be a high-quality eco-tourism provider
catering for niche markets” May be several, sometimes conflicting Used as basis for critical success factors,
measures of performance Sounds familiar? Could be root definitions, perhaps
several based on different W’s.
Logical Activity Model Business activities that must be carried
out and the dependencies between them Modelled with control systems, feedback
etc.
Sounds familiar? Could be conceptual models, especially
CPTM.
SSM in Business Activity Modelling
SSM gives one possible approach – based on Wilson’s techniques
Create root definitions (Business perspectives included)
Derive Primary Task Models for essential activities
Derive Consensus Model “Test against reality”
The RD is “What they believe their business to be.”(SSADM4+ User Guide)
Link to requirements Extract functional requirements from CPTM
Requirements Catalogue Convert CPTM to required system Data Flow
Model Define external entities Convert activities to processes within or outside
system boundary (decompose?) Identify information support where activities are
outside boundary, & define system functions to provide it
Specify performance modelling data Define data stores
Link to Work PracticeCPTM contributes to Work Practice
Model Identify activities that could be
automated Map onto organisation structure and
geography User roles Locations May need to decompose activities
SSM in SSADM feasibility
SSM may be used before a feasibility study instead of a feasibility study as part of a feasibility study
Detailed guidance published (CCTA, 1993)
SSM deliverables in SSADM Feasibility
Help define the scope of the study (rich picture) Suggest/confirm key entities for data model (RD) Help decide what current systems analysis to do (RD, CM) Identify functional & non-functional requirements (RD, CM, CPTM) Identify & scope feasibility options (CM, Maltese Cross) Identify information requirements & gaps in existing provision
(Maltese cross, Information activity table) Identify users Help produce & check data flow models (CPTM, information
categories) Identify service levels and management information (measures of
performance)
SSM has also been used with…
UML – linked to use cases or activity diagrams Other OO methods, (Schlaer-Mellor, Galvin & Lane
(1999)) DFDs – several attempts (see Mingers, 1995) Multiview – a method for small systems, with an SSM-
based first phase. Also Multiview 2 – OO. LOTOS (formal method) JSD (Pre-OO method) Information Engineering (for strategy planning) Prototyping etc.
SSM & IS – summary of uses
In information strategy planning To decide what systems should be
built As an aid to scoping systems In a feasibility study - or instead of
one For finding information requirements To aid acceptance of systems Dealing with IS-related problems
In these two weeks, we have Learned the structure and techniques of
SSM Seen how to map SSM models onto
information requirements using Wilson’s approach
Seen, briefly, some other uses of SSM in the IS field
Discussed why we might want to do this.
Follow-up & preparation Finish workbook (if you haven’t) Prepare for seminar – section 7 of
workbook Further reading as specified in
workbook, and dip into the items on Wilson’s approach.
References & Further Reading
On Wilson’s approach –any of these is a good start. Wilson, (1990), Systems: Concepts, Methodologies, and
Applications, 2nd edn. Wiley. Chapter 6. (Or pp. 193-247 1st edn.)
CCTA (1993) Applying Soft Systems Methodology to an SSADM Feasibility Study, London: HMSO. Chapter 4.
Grant, K & Stansfield, M, “Matching Technology with Organisational Needs: Bridging the Systems Thinking Paradigm – A Practical Approach.” http://floti.bell.ac.uk/kevingrant/paper2.htm
References/Bibliography Wilson’s approach
B. Wilson (2001), Soft Systems Methodology: Conceptual Model Building and its contribution, Wiley.
Overview of the field inc. Wilson, DFD. J. Mingers (1995), ch. 2 in F. Stowell (ed),
Information Systems Provision: the Contribution of Soft Systems Methodology, McGraw-Hill.
On rationale for using SSM for IS M.C. Winter, D.H. Brown & P.B.Checkland (1995),
“A role for soft systems methodology in information systems development,” European Journal of Information Systems 4, pp. 130-142.
References/Bibliography SSADM
CCTA (1993) Applying Soft Systems Methodology to an SSADM Feasibility Study, London: HMSO. Chapter 4. (Reference book in library)
CCTA (1995), SSADM 4+ User Guide, NCC Blackwell Multiview
D. E. Avison & G. Fitzgerald (1995), Information Systems Development: Methodologies, Techniques and Tools, McGraw-Hill. Section 6.2.
D.E. Avison & T. Wood-Harper (1990), Multiview, An exploration in Information Systems Development, McGraw-Hill.
References On Failure
Bennett, McRobb & Farmer, Object-Oriented Systems Analysis and Design using UML, McGraw-Hill. Section 2.3 (both editions)
OO approach Lane, K. & Galvin, C. (1999) “Methods for Transitioning
from Soft Systems Methodology (SSM) Models to Object Oriented Analysis (OOA), developed to support the Army Operational Architecture (AOA) and an Example of its Application.”
http://www.dodccrp.org/1999CCRTS/pdf_files/track_6/092galvi.pdf [Viewed October 04]