Comparative Development Methodologies Revision Lecture

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Comparative Development MethodologiesRevision
Lecture

• Niki Trigoni
• Department of Computer Science
• and Information Systems
• Birkbeck College, University of London
• Email niki_at_dcs.bbk.ac.uk
• Office Hours Wednesdays, 6 - 7 pm
• Web Page http//www.dcs.bbk.ac.uk/niki

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Revision lecture roadmap

• Outline of the main material covered in the
  second half of CDM sample questions that one
  should be able to answer (not an exhaustive list)
• Guidelines for writing exams
• Discussion

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Development methodologies

• A methodology is a recommended series of steps to
  be followed in the course of developing an
  information system. It has several components
• Philosophy
• Phases
• Procedures, rules
• Tools, techniques
• Documentation
• Management and training for developers

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Types of methodologies

• Process-oriented methodologies
• Blended methodologies
• Object-oriented methodologies
• Rapid development methodologies
• Organizational-oriented methodologies

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Process-oriented methodologies

• Emphasis is placed on the analysis of processes
• STRADIS (Structured Analysis and Design of
  Information Systems) has a top-down approach to
  analyzing processes
• YSM (Yourdon Systems Method) has a middle-up
  approach to analyzing processes and puts emphasis
  on the analysis of data

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STRADIS

• Does it focus on analysis or design?
• Is it applicable to information systems
  independent of their size or level of automation?
• For which scenario is STRADIS particularly
  suitable?
• Which is the most important idea used in STRADIS?
  
• How many stages does it have and which activities
  are carried out in each stage?

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YSM (Yourdon Systems Method)

• How does YSM resemble STRADIS?
• How is YSM different from STRADIS?
• Which are the stages of YSM, and which tasks are
  performed in each stage?
• What is the purpose of essential modeling (stage
  2 of YSM)?
• What is the difference between the environmental
  and behavioral models of essential modeling in
  YSM?

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Blended methodologies

• Emphasis is placed on the analysis of processes
  and data
• SSADM (Structured Systems Analysis and Design
  Methodology) is a standard methodology in most UK
  government applications. It has detailed steps
  and guidelines and standard documentation
  templates
• Merise is a widely used methodology in France. It
  regards data and processes as equally important,
  and analyzes them in parallel.
• IE (Information Engineering) has more emphasis on
  data, considered to be the most stable part of a
  system. It takes a data-oriented
  entity-relationship approach, but also includes
  process-oriented aspects.

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SSADM

• Would you choose SSADM if you would like a
  flexible and light development strategy without
  predefined steps and the need for documentation?
• Which are the stages of SSADM and which tasks do
  they involve?
• Would SSADM be sufficient as a methodology if the
  goal is to do analyze, design, implement and
  maintain a system?

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Merise

• Which are the objectives of the decision, life
  and abstraction cycles in Merise?
• Which stages (phases) constitute the life cycle?
• Explain the differences of conceptual, logical
  and physical levels of concern for data and
  processing in the abstraction cycle.

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IE (Information Engineering)

• Which is the main philosophical belief
  underpinning IE?
• Does IE cover all stages of a systems lifecycle?
• Which are the stages of IE and which tasks to
  they involve?
• What is the main difference between IE and SSADM
  or Merise?

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Object-oriented methodologies

• The UP (Unified Process) is an iterative
  methodology that uses the object-oriented
  paradigm for analysis and design.
• Which are the central ideas in the UP?
• Which are the UP phases, and how do they relate
  with the UP iterations?
• Name the main disciplines of the UP, and discuss
  when they are applied.

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The Unified Process

• Can you identify and reproduce domain model
  diagrams, DCDs and interaction diagrams? What is
  the diagram below?

Sales LineItem quantity
Item
Records-sale-of
0..1
1
1..
Contained-in
1
Sale date time
Payment amount
Paid-by
1
1
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The Unified Process
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The Unified Process
Sample UP Disciplines
Business modeling
Requirements
Design
Implementation
Test
Deployment
Configuration and Change Mngmnt
Project Mngmnt
Environment
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Rapid development methodologies

• XP (Extreme Programming) aims at speeding up the
  development process in order to cope with rapidly
  changing business needs.
• In which scenarios is XP particularly suitable?
• Would you apply XP to a large system development
  project?
• How is XP different from Process-oriented,
  Blended and OO methodologies?
• Which are the main ideas in XP?
• Which are the XP phases and which tasks do they
  include?

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Organizational-oriented methodologies

• In some organizational problem situations, it is
  not enough to break up a complex situation into
  its constituent parts in order to solve it
• The whole is greater than the sum of the parts
• Human activity systems it is relatively easy to
  model data and processes (like in previous
  methodologies) but to understand the real world
  it is essential to include people in the model
• Hard-systems thinking vs. soft-systems thinking
• Soft Systems Methodology (SSM)

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SSM

• Which are the stages of SSM and which tasks do
  they include?
• Which kind of problems is SSM suitable for?
• Does SSM implement a system? If not what is the
  main outcome of SSM?

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Issues rationale for a methodology

• A better end product
• Acceptability (do people find the product
  satisfactory?)
• Availability (is the product accessible
  when/where required?)
• Cohesiveness (are information and manual systems
  integrated?)
• Compatibility (does the system fit with other
  parts of the organization?)
• Documentation
• Ease of learning
• Economy (is the system cost effective, within
  resources and constraints?)
• Effectiveness (does the system meet
  business/organizational objectives?)
• Efficiency (does the system utilizes resources to
  their best advantage?)
• Fast development rate (time relative to project
  size and complexity)
• Flexibility (is the system easily modifiable?)
• Functionality (does the system cater for the
  requirements?)
• Implementability (feasible changeover from the
  old to the new system?)
• Low coupling (is there low interaction between
  subsystems so that changes of one does not affect
  the others significantly?)

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Issues rationale for a methodology

• A better development process
• Tight control of the development process
• Well-specified deliverables at each stage
• Improved management, planning and project control
• Increase of productivity
• Reduction of skills required of analysts gt
  reduction of cost
• A standardized process
• Staff can change between projects without
  retraining
• Common experience and knowledge can be
  accumulated
• Easy system maintenance
• Better systems integration

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Issues adopting a methodology in practice

• Variation points of different methodologies
• fully fledged product detailing every stage and
  task or vague outline of basic principles
• high-level strategic and organizational problem
  solving or details of implementing a computer
  system
• conceptual issues or physical design procedures
  or the whole range of intermediate stages
• applicable to specific problem types or
  all-encompassing general-purpose methodology
• usable with or without special training
• people it requires to complete tasks (if
  specified)
• tools and toolsets used

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Methodology comparison framework

• Philosophy
• Paradigm
• Objectives
• Domain
• Target
• Model
• Techniques and tools
• Scope
• Outputs
• Practice
• Background
• User base
• Participants
• Product

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Method. comp. framework philosophy

• Philosophy (cont.)
• Four distinguishing factors (cont.)
• Domain situations that methodologies address
• narrow problem vs. wider organization-level
  problems
• individual problems vs. many interrelated
  problems viewed as a whole
• Target applicability of the methodology
• general-purpose vs. application/organization
  specific

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Method. comp. framework model

• Model abstraction and representation of the
  important factors of the information system or
  the organization
• Verbal
• Analytic or mathematical
• Iconic, pictorial or schematic
• Simulation
• Most methodologies are iconic, pictorial or
  schematic.
• Models are used as a means of communication,
  particularly between users and analysts

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Method. comp. fram. techniques tools

• Techniques and Tools
• Are techniques and tools essential to the
  methodology?
• Which techniques/tools are used in a methodology?
• Examples
• Rich pictures, root definitions, etc
• Entity modeling and normalization
• DFDs, decision tables, decision trees, entity
  life cycles
• OO design and UML
• Various organizational and people techniques

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Method. comp. framework scope

• Scope indication of the stages of the life cycle
  of systems development that the methodology
  covers
• Recall SDLC (Systems development life cycle)
• Feasibility study
• System investigation
• Systems analysis
• Systems design
• Implementation
• Review and maintenance

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Method. comp. fram. outputs product

• Outputs what the methodology is producing
• Deliverables at each stage
• Nature of final deliverable
• Decision about whether to computerize a process
• Analysis specification
• Working implementation of a system
• Product what purchasers actually get for their
  money
• Software
• Written documentation
• Agreed number of hours training, consultancy
• Telephone help service
• ...

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Method. comp. framework practice

• Practice
• Methodology background academic vs. commercial
• User base numbers and types of users
• Participants and skill levels required
• Assessment of difficulties and problems
  encountered
• Perception of success and failure
• Degree to which the methodology is altered by the
  users according to the requirements of the
  situation
• Differences between the theory and the practice
  of the methodology

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Summary

• We considered a number of different methodologies
  (STRADIS, YSM, SSADM, Merise, IE, UP, XP, SSM)
• We compared them in terms of
• Philosophy, model, techniques and tools, scope,
  outputs, product and practice
• Given a certain scenario, we should be able to
  make an educated decision about which (type of)
  methodology is the most suitable.

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Tips for exams

• Allocate time cautiously dont spend too much
  time on a single question.
• Read the questions carefully. Sometimes we tend
  to answer what we want to be asked, rather than
  what we are actually asked.
• Make your answers legible.
• At the end, look over your answers to see what
  you have done.
• Dont make your answers too long be concise.

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Examination paper

• Date of examination 10.00 am, Monday 13th June
  2005
• Duration of paper 2 hours
• The paper is divided into two sections
• Section A (answer only one question out of two)
• Section B (answer only two questions out of four)
• Overall answer three questions (one from Sect. A,
  and two from Sect. B)
• Each question has 33 marks
• You get 1 extra mark if you write the question
  numbers that you selected to answer in the front
  page of the exam paper.
• Total marks 333 1 100

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Good luck! Questions?