1. COM332 – SA3
SSADM, MERISE

2. SDLC SDLC has had an enormous influence in systems development
Follows the structure
Feasibility study
Systems investigation
Systems analysis
Systems design
Implementation
Review and maintenance
The term life cycle indicates the staged nature of the process
By the time the review stage comes the IS may found inadequate
Process start again with feasibility study

3. Strengths
Methodologies incorporating this view have been well tried and tested
The use of documentation standards ensures
The specifications are completed
Communicated to systems developers, users and computer operations staff
People are trained to use the system
Prevent missing cut over dates (to an extent)
Users have opportunity to review the progress at the end of each phase
Divide the system development onto phases, subdivide to more manageable tasks

4. Weaknesses Failure to meet the needs of the management Instability
Instead of meeting corporative objectives computer are used to help low-level operational tasks
Instability
As business changes processes need to change to adapt to the new environment
Models of processes are unstable
Computer model processes have to be modified
Inflexibility
Systems ends (outputs) are decided in the early stages of the system development
Design is output driven – designed from the outputs backwards

5. Weaknesses User dissatisfaction Problems with documentation
Difficult to incorporate the changes once the development is underway
Users asked to sign off the requirement specification in early stages of development
A document prepared by the analysts, operational staff and programming staff
Users first see the system on implementation and find it inappropriate
Problems with documentation
Documentation focused on the computer person, not on the user
Lack of control
Problems in estimating time, people and other resources needed due to the complexity of some phases and the inexperience of the estimators

6. Weaknesses Incomplete systems Application backlog Maintenance workload
Exceptions are being ignored or forgotten
Application backlog
Users have to wait some years before the development process can get underway
Development may take many months or years to complete
Maintenance workload
Quick and dirty solutions – high maintenance
Problems with the ideal approach
SDLC assumes a step-by-step, top-down approach
Information systems development is an interactive process

7. Weaknesses Emphasis on hard thinking
SDLC makes a number of assumptions
There are facts that only need to be investigated and identified, there can be a best solution identified to ,solve the problem which can be easily engineered by following a step-by-step approach
World of IS is concerned with people and organisation
The situation encountered are problematic, ambiguous and messy
Assumption of green-field development
SDLC assumes all systems developed are new, there are no existing system

8. Major concerns in computing
Meeting project deadlines
System maintenance
Staff recruitment and retention
User dissatisfaction
Changing requirements

9. Methodologies Process oriented Blended Object oriented
Rapid development
People oriented
Organisational oriented
Frameworks

10. SSADM Life cycle approach
Developed by Learmonth & Burchett Management Systems (LBMS) and CCTA
Used in government applications since 1981
Highly structured
Has seven stages
Activities and their end product of each stages are precisely defined
Facilitates the use of project management method like PRINCE
Cover the life sycle from feasibility to design but not implementation and maintenance

11. Stage 1 Investigation of current environment
Stage 0 Feasibility
Define scope of project
Stage 1 Investigation of current environment
Model existing system
Stage 2 Business system options
Business (logical) solutions
Stage 3 Definition of requirements
Transform user requirements into a specification
Stage 4 Technical system options
Different platforms
Stage 5 Logical design
Model proposed system
[Stages 4 and 5 in parallel]
Stage 6 Physical design
Translate to physical system

12. Investigation of current environment
Results of feasibility study are examined
Scope of the project reassessed
Overall plan is agreed with management

13. BSO (Business system option)
Functionality of the new system is determined and agreed
A number of business options where outlined each includes
Outline of its cost 
Approximate Development time scale
Known technical constraints
Organisation of the system (online/offline, interface to other systems, distribution)
Approximate data & transaction volumes
Training requirements
Major benefits to the business
Impact on the organisation and on other existing systems
DFD and ERD are developed – specification narrative

14. Definition of requirements
Full requirement specification and clear guidance to the design stages
Centre of SSADM
Investigation and analysis are replaced by specification and design
DFD is used to communicate with the user
User roles are defined
Entity model is extended and followed by normalisation
Components of each function (input, output, events or enquiry triggers) are defined
Optional prototyping for better understanding of user’s requirement

15. TSO (technical system option)
The environment in which the systems operates in terms of
Hardware platforms
Software (3GL, 4GL ...)
Development method
Technical support arrangements (in-house, outsourced, contract staff)
Are determined

16. Logical design Physical design What the systems id required to do
Dialogue structure, menu structure and design are defined for particular user roles
User involvement is recommended
Physical design
Logical design is mapped to a particular physical environment

17. MERISE Widely used methodology in France
The essentials of this approach lies in three cycles
Decision cycle
Relates to various decision mechanisms
Life cycle
Chronological progress of the project from start to finish
Abstraction cycle
Various models for processes and data
Cover data and process elements with equal emphasis
permits the participation of end-users, senior management and data professionals in its decision cycle

18. Decision Cycle Referred as approval cycle
Consists of all decision mechanisms
Decisions will include
Technical choices regarding hardware and software
Processing choices such as real-time or batch
User-oriented choices relating to the user interface
Identification decisions regarding the major actors of the IS and the organisation
Financial decisions relating to costs and benefits
Management decisions concerning the functionality of the ISs
Each decision point is identified
Identified who takes the decision
Groups of users and system developers together discuss various options, user team produce report, discussed at the joint meeting of senior management, users and application developers. Decision is made at this point

19. Life cycle Strategic planning Preliminary study (domain)
Maps the goals of the organisation to its information needs, and partition of organisation into domains for further analysis
Preliminary study (domain)
Describes the proposed information system, discuss their likely impacts, and details the associated costs and benefits
Detailed study (system) 
Those aspects which will be automated, including detailed specification for functional design
Schedules and other documentation
Development
Implementation
Maintenance

20. Abstraction cycle Key to Merise
Data and processes modelled through three stages
Goes from knowledge of the problem area, to making decisions relating to resources and tasks, through technical means on which to implement it
Conceptual stage looks at organisation, logical stage addresses questions. Physical stage looks at resources and technical constraints.

21. Level Concern Data Process Conceptual What do you want to do
Conceptual data model
Conceptual process model
Logical or Organisational
Who does what, where, when, how
Logical data model
Logical or Organisational data model
Physical or operational
By what means
Physical data model
Operational processing model

22. Conceptual level establish what to do
At the Logical level all the organisational alternatives are identified
Identifying organisational processes, how the processes are carried out, who carries out
Logical model transforms the conceptual model into a form that suitable for computerisation
Deciding the database
Physical level technical alternatives are identified
Answer the question with what means

23. Merise – advantages Well tried and tested
Covers strategic plan as well as life cycle from prelim study through development, implementation, maintenance, decline and replacement
3-level abstraction cycle covers data and process elements with equal emphasis
Prescriptive to some extent but enables participation of end-users and senior management in decision cycle
Attempts to take into account new needs and directions
Many support tools available

24. Most important aspect of Merise
Rules for creation of models
Rules for converting from one stage to another
Assumption that change is common so modifications will be required
Support tools available