روش شناسی توسعه سیستم های...
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روشهای ترکیبی BLENDED METHODOLOGIES
روش شناسی توسعه سیستم های اطالعاتی
Structured Systems Analysis and Design Method
SSADM
Background
is a methodology developed originally by UK
SSADM has been used in a number of government applications since 1981, and its use was mandatory in many Civil Service applications.
Therefore the most important aspect of the STRADIS methodology is the bringing together of many of the techniques
The methodology provides project development staff with very detailed rules and guidelines to work to. It is highly structured.
SSADM has seven stages within a five 'module' framework (the bullet points) with its own set of plans, times scales, controls, and monitoring procedures.
Phases
Feasibility Study
•o Feasibility
Requirements analysis
•1 Investigation of current environment •2 Business systems options
Requirements specification
•4 Technical system options
•5 Logical design
Logical system
specification
Physical design
3. Definition of requirements
6. Physical design
Phases: Feasibility Study
This stage is concerned with ensuring that the project which has been suggested in the planning phase is feasible;
Prepare for the feasibility study
Define the problem
Select feasibility options
Create feasibility report
Phase: Requirements analysis
1. Investigation of current environment Repeats much of the work carried out at the feasibility study stage but in more detail. Establish analysis framework Investigate and define requirements Investigate current processing Investigate current data Derive logical view of current services Assemble investigation results
2. Business systems options It is at this stage that the functionality of the new system is determined and agreed.
Define business system options Select business system options Define requirements
Phase: Requirements Specification
3. Definition of requirements This stage leads to the full requirements specification and provides clear guidance to the design stages, which follow.
Define required system processing
Develop required data model
Derive system functions -Enhance required data model
Develop specification prototypes
Develop processing specification
Confirm system objectives
Assemble requirements specification
Phase: Logical System Specification
4. Technical system options This stage and the following logical design stage are carried out in parallel. In the technical system options stage, the environment in which the system will operate, in terms of the hardware and software configuration, development strategy, organizational impact and system functionality, is determined. Define technical system options Select technical system options Define physical design module
5. Logical design This is a statement of what the system is required to do rather than
a statement about the procedures or program specifications to do it. Define user dialogues Define update processes Define enquiry process Assemble logical design
Phase: Physical design
6. Physical design Prepare for physical design
Create physical data design
Create function component implementation map
Optimize physical data design
Complete function specification
Consolidate process data interface
Assemble physical design
Merise
Merise d'analyse Méthode
Background
Merise is the most widely used methodology for developing information systems in France.
Like SSADM, Merise has become influential in the European approach, Euromethod
The essentials of the approach lie in its three cycles: the decision cycle, the life cycle, and the abstraction cycle, which cover data and process elements with equal emphasis.
The project which led to Merise was launched by the French Ministry of Industry
The core of the Merise approach lies in its three cycles: the decision cycle, which relates to the various decision mechanisms; the life cycle, which reflects the chronological process of a Merise project from start to finish; and the abstraction cycle, the key to Merise, which describes the various models for processes and data in each of three stages
Phases:
decission Cycle
• o Feasibility
Life cycle
• 1 Investigation of current environment
• 2 Business systems options
abstraction cycle
• 4 Technical system options
• 5 Logical design
Phases: Decision Cycle
The decision cycle, sometimes referred to as the approval cycle, consists of all the decision mechanisms, including those for choosing options, during the development of the information system.
Decision making is a joint process concerning senior management, users, and systems developers.
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 information
system and the organization; financial decisions relating to costs and benefits; management decisions concerning the functionality of the information
systems.
Phases: Life Cycle
The life cycle shows the chronological progress of the information system from its creation, through its development, until its final review and obsolescence
The main phases of the life cycle are: Strategic planning (at the corporate level) Preliminary study (for the domain of interest)
Detailed study (for a particular project)
Schedules and other documentation
The whole of this second cycle is similar to the conventional life cycle as found, for example, in SSADM and other methodologies
Phases: Abstraction Cycle
The abstraction cycle is the key to Merise.
Unlike many alternative approaches, the separate treatment of data and processes is equally thorough and both are taken into account from the start.
The data view is modelled in three stages:
the conceptual,
the logical,
through to the physical.
Phases: Abstraction Cycle
similarly, the process-oriented view is modelled through the equivalent three stages of
conceptual,
organizational, and
Operational The abstraction cycle is a gradually descending approach which goes from the knowledge of the problem area (conceptual), to making decisions relating to resources and tasks, through to the technical means on which to implement it.
.
Enterprise
Resource Planning
Welti ERP
Background
In this section we consider Norbert Welti's approach to developing EPdP projects, as described in Welti (1999).
he description is based on his experience implementing SAP R/3 projects, which is the most common ERP solution base, but the approach can be used for other ERP proj-
The ERP system, along with the organizations in which it is implemented, is large and complex.
The components of SAP R/3, for example, include separate modules for financial accounting, controlling, fixed assets management, project systems, workflow, industry solutions, human resources, plant maintenance, quality management, production planning, materials management, and sales and distribution.
Phases:
Phases: ASAP
SAP itself has developed a methodology called Accelerated SAP or ASAP, which is designed for smaller and more straightforward ERP projects. The methodology has six phases:
Project preparation.
Design business blueprint.
Simulation.
Validation.
Final preparation.
Support.
Information
Engineering
IE
Background
The origins of Information Engineering (IE) differ according to which source is referenced.
It appears that Clive Finkelstein first used the term to describe a data modelling methodology that he developed in Australia in the late 1970s.
In the same year he collaborated with James Martin on a two-volume book entitled Information Engineering (Martin and Finkelslein, 1981)
There also exist a number of variants of IE for different development environments. These include a package-based approach, a Rapid Application Development (RAD) approach (see Section 23.1) and an object-oriented-based version (Martin and Odell, 1992).
IE is claimed to be a comprehensive methodology covering all aspects of the life cycle.
It is viewed as a framework within which a variety of techniques are used to develop good quality information systems in an efficient way.
About IE
There are a number of philosophical beliefs underpinning IE. One of the original was the belief that data are at the heart of an information system
and that the data, or rather the types of data, are considerably more stable than the processes or procedures that act upon the data.
the most appropriate way of communication within the methodology is through the use of diagrams.
Methodologies which are based only upon processes are likely to fail due to the constantly shifting nature of this base as requirements change.
However, IE also clearly recognizes that processes have to be considered in detail in the development of an information system and balances the modeling of data and processes as appropriate.
Each IE technique is oriented toward diagramming, and a diagram is a deliverable of each major stage in the methodology.
About IE
The primary IE model consists of three components: data, activity, and the interaction of the data and activities
The interaction may be a matrix indicating at a high level which subject areas are used in which functions. At a lower level it may show which entity types are used by which processes. At an even lower level still, the interaction may be expressed as an action diagram and finally as actual program code.
About IE
The methodology is top-down and begins with a top management overview of the enterprise as a whole.
Phases:
Phases1: Information Strategy Planning
Much of this level is really concerned with the overall corporate objectives. It may not always be part of the IE methodology, as it would normally be performed by corporate management
However, it is recognized as a fundamental starting point for the methodology
The corporate or business plan should indicate the business goals and strategies, outline the major business functions and their objectives, and identify the organizational structure.
ISP involves an overview analysis of the business objectives of the organization and its major business functions and information needs.
The result of this analysis is what is termed 'information architectures' which form the basis for subsequent developments and ensure consistency and coherence between different systems in the organization
The resulting information strategy plan documents the business requirements and allocates priorities, which are the rationale for the development of the information systems.
Phases1: Information Strategy Planning
Information strategy planning is a joint activity of senior general management, user management, and information systems staff. It involves the performance of four tasks as follows: 1-1 Current situation analysis.
1-2 Executive requirements analysis- Critical success factors (CSFs)
for the overall organization are identified, and these are also decomposed into CSFs for the individual parts of the organization
1-3 Architecture definition
1-4 Information strategy plan.
Phases1: Information Strategy Planning
1-1 Architecture definition
This is an overview of the area in terms of information (the identification of global entity types and the decomposition of functions within the subject areas
an analysis of distribution (the geographic requirements for the functions and the data)
a definition of business systems architecture (a statement of the ideal systems required in the organization)
a definition of technical architecture (a statement of the technology direction required to support the systems including hardware, software, and communications facilities),
and a definition of information system organization
Phases1: Information Strategy Planning
1-2 Information strategy plan- includes:
the determination of business areas
the preparation of business evaluations (strategies for achieving the architectures, including migration plans for moving from the current situation to the desired objective),
the preparation of the information strategy plan itself (a chosen strategy including priorities for development and work programs for high-priority projects).
Phases2: Business area analysis
2-1 Entity and function analysis. It involves:
the analysis of entity types and relationships,
the analysis of processes and dependencies,
the construction of diagrammatic representations of the above,
Phases2: Business area analysis
2-2 Interaction analysis. This examines the relationship and interactions between the data and the functions, that is, the business dynamics. the analysis of entity types and
relationships,
the analysis of processes and dependencies,
the construction of diagrammatic representations of the above,
Phases2: Business area analysis
2-3 Current systems analysis.
This models the existing systems
2-4 Confirmation.
2-5 Planning for design
Phases3: System planning and design
This level is divided into business system design and technical design. business system design:
Preliminary data structure design System structure design. Procedure design. Confirmation. Planning for technical design.
technical design: Data design –
Software design
Cutover design
Operations design
Verification of design
System test design
Implementation planning
The output from this stage is the technical specification, including the hardware and software environment, its use, standards, and conventions. It also includes the plan and resources for subsequent construction and cutover.
Phases4: Construction and cutover
This level includes the stages of construction, cutover, and production
Construction consists of: System generation
System verification
Cut over consists of: Preparation
Installation of new software
Final acceptance
Fan-out
System variant development
Conclusion: Blended Methodologies
They are blended, that is, being formed from parts of, or perhaps, the 'best of, other methodologies, techniques, and tools (and applications in the case of ERP).