SSM - PowerPoint PPT Presentation

1 / 40
About This Presentation
Title:

SSM

Description:

SSM & Information Systems Wilson s approach to defining information requirements from conceptual models. Why SSM for IS? How has it been applied? – PowerPoint PPT presentation

Number of Views:268
Avg rating:3.0/5.0
Slides: 41
Provided by: Zon9
Category:

less

Transcript and Presenter's Notes

Title: SSM


1
SSM Information Systems
  • Wilsons approach to defining information
    requirements from conceptual models.
  • Why SSM for IS?
  • How has it been applied?

2
SSM Overview
Choosing building models of relevant systems
of purposeful activity, each based on a world-view
Finding out about the problem situation,
including cultural/ political aspects

-




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





3
SSM for IS definition based on Wilsons approach
To design
Map to organisation (role-role flows)
Map activities to IPPs
(Adapted from Wilson, 1990)
4
Wilsons 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 (IPPs).
  • Role - a position in the organisation. Roles are
    responsible for activities.

5
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.

6
Consensus models - comparing models
  • We can compare different (primary task) models
    based on different Ws.
  • One of these will be based on a neutral primary
    task description something essential that
    no-one will dispute.

7
Consensus models - agreed activities
  • Take the neutral models activities
  • Examine other models activities
  • Add others after seeking agreement /
    accommodation
  • Choose activities that give a coherent model

?
?
8
Producing the CPTM
Individual models
4 Compare test model with tentative consensus
model
Consensus PTM
(CCTA, 1993)
9
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

10
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 Ws 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.

11
SSM for IS definition based on Wilsons approach
To design
Map to organisation (role-role flows)
(Adapted from Wilson, 1990)
12
Information categories
  • Information data meaning.
  • Information categories are therefore not just
    data items, but are defined in a way that
    indicates how theyre used.
  • E.g. Stock availability rather than quantity
  • Define the data in each category
  • Lower level models tend to have more detailed
    information categories.

13
Simple way to show information requirements
Available products
Purchase orders
3
Re-order goods
  • What information does it require?
  • What information does it produce?

Stock levels
14
Input/output table
15
SSM for IS definition based on Wilsons approach
To design
Map to organisation (role-role flows)
(Adapted from Wilson, 1990)
16
Maltese Cross
N
E
W
S
17
Maltese Cross
Check order Despatch goods
Stock levels Stock card - item no qty
Orders Order record
Stock levels Stock card - item no qty
Orders Order record
N S
E W
Item file - quantity available
Item file - quantity available
X
X
X
Sales OP
X
X
Stock ctrl
Debtors
X
Current IPPs
18
Organisational mapping
  • What role is responsible for each activity?

Sales Mgr
19
Wilsons 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.

20
Wilsons 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 IPPs.)
  • 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.

21
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.

22
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.

23
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.

24
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
  • (Flynn, in Bennett et al. section 2.3)

25
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)

26
SSADM 4 Business Modelling
  • An 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)

27
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 Ws.

28
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.

29
SSM in Business Activity Modelling
  • SSM gives one possible approach based on
    Wilsons 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)
30
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

31
Link to Work Practice
  • CPTM 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

32
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)

33
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)

34
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.

35
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

36
In these two weeks, we have
  • Learned the structure and techniques of SSM
  • Seen how to map SSM models onto information
    requirements using Wilsons approach
  • Seen, briefly, some other uses of SSM in the IS
    field
  • Discussed why we might want to do this.

37
Follow-up preparation
  • Finish workbook (if you havent)
  • Prepare for seminar section 7 of workbook
  • Further reading as specified in workbook, and dip
    into the items on Wilsons approach.

38
References Further Reading
  • On Wilsons 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 

39
References/Bibliography
  • Wilsons 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.

40
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.

41
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
Write a Comment
User Comments (0)
About PowerShow.com