File Name: structured systems analysis and design methodology .zip
It is the UK government's standard method for carrying out the system analysis and design stages of an information technology project. SSADM has been traditionally used for the development of medium or large systems. SSADM starts from defining the information system strategy and then develops a feasibility study module.
This is why it is mainly designed for large-scale Information Systems with high volume business events. SSADM specifies exactly the flows and tasks of a development project and produces a detailed documentation of the project. SSADM sticks to the traditional waterfall model, which allows review of each stage but requires its accomplishment before the next one can begin.
Its main benefits are: Improvement of quality, detailed documentation of the development stages, and reusability for similar projects that follow. But these points are not likely to be taken into consideration in practice. This is due to the danger of over-analysing, which can be very time and -cost consuming. Especially for small or medium-sized companies, huge delays can lead to serious financial and resource problems. So, it is highly advisable to investigate alternative methods, such as the Rapid Application Development RAD or to use an off-the-shelf product, which is much less expensive and less time-consuming and has already been tested by various other companies.
In the late seventies, large-scale Information Systems IS became popular in order to manage large systems for billing, salaries, stock control and other applications requiring huge databases. Many organisations did not have an appropriate development method.
First of all, analysis of the systems requirements was carried out on an ad hoc basis, so often the final product did not exactly meet the business requirements. Time consuming 3GL programming languages, such as Cobol, were used and the produced files and databases were inflexible.
To overcome these problems, the IS community decided to develop a methodology e. It was especially designed for government departments and their external providers of software, where there was a great need for Information Systems and hope to improve their IS by using a disciplined engineering method. So, one should consider carefully if it is suitable for the system that needs to be developed in respect of the systems size and purpose.
Companies, mainly, who have information systems to manage, i. It is assumed that in general large companies need to produce large information Systems and small or medium-sized companies produce smaller information systems. These points are essential to deliver the product on time. Simultaneously, the systems model is developed and a comprehensive demand analysis is carried out. Both are tried to see if they are well suited to each other. This offers the possibility to tailor the planning of the project to the actual requirements of the business.
Effective use of skills: SSADM does not require very special skills and can easily be taught to the staff. Normally, common modelling and diagramming tools are used. Better quality: SSADM reduces the error rate of IS by defining a certain quality level in the beginning and constantly checking the system. Improvement of productivity: By encouraging on-time delivery, meeting business requirements, ensuring better quality, using human resources effectively as well as trying to avoid bureaucracy, SSADM improves the overall productivity of the specific project and the company.
So the system does not have to be implemented again with new hard -or software. SSADM puts special emphasis on the analysis of the system and its documentation. This causes the danger of over-analysing, which can be very time and cost consuming. Especially with large systems, the outline diagram can become very unclear, because all relevant data flows have to be included.
However, large companies carrying out various projects, can profit from the fact that SSADM gives the possibility to reuse certain techniques and tools for other projects. This reduces cost and time spent enormously in the long run.
So, the danger of spending too much money on analysis can be compensated by the reuse of the developed systems and experience gained. Small or medium sized companies are normally not involved in such high volume business projects.
The great advantage of smaller companies is, normally, that they are more flexible and less bureaucratic than large companies. Although SSADM sees its long term benefits in more flexibility and time saving reuse of certain methods , there are still doubts about whether this could be a valuable method for medium sized companies.
If a system is being developed, for which standard methods and CASE tools can be used and it turns out that inhouse development is much more expensive and more time consuming, SSADM is a good solution. Another solution could be to produce cut-down versions of SSADM in order to make it suitable for another project, which is probably smaller.
So, the company could benefit from the fact that the staff is already trained and experienced. Within this process the data requirements of an IS are investigated, identified, modelled and documented. The logical data structure LDS is formed. It gives information on the entities that need to be put down and on the relationships between these entities.
Data Flow Diagrams are used to describe the system in different levels of abstraction. They model functionality and show how input transforms into output. Entity Relation Diagrams represent objects and their relationships. They normally show the important entities and relations but no attributes.
Again a comprehensive DFD is produced. The transformation of the processes, however, are more likely to be represented in a distinct description of processes. Furthermore, the DFD shows the data stores, which could be directories, folders, servers and the way they are accessed. A description of the external entities persons or companies that do not belong to the systems but are relevant to it should be included, too.
Finally, data flows between processes, data stores and external entities are also represented. The process of Entity Event Modelling deals with the business events that have an impact on each entity and its surrounding. This information is put down in a so called Entity Life Histories 16 file.
Finally, for each process, data flow, data store and external entity there is an entry in the so called data dictionary. This data dictionary is the central catalogue of data within an IS. It shows the structure, storage, connections, origin and use of data. The data dictionary aims to give the possibility of describing the elementary data in an appropriate verbal way. Although this system will meet its requirements perfectly and be of very good quality, the use of a formal structured methodology like SSADM is very time-consuming.
Especially for small or medium-sized companies such huge delays can lead to serious financial and resource problems, even to bankruptcy.
The next paragraph will give an insight in the different stages of SSADM and when they have to be completed. This is probably the most important reason, why SSADM is, on the one hand, very time-consuming, but, on the other hand, widely regarded as an improvement to the quality of a system.
Investigation of economical and technical feasibility. The problems are defined and the project identified. The best business option is chosen out of up to 5 propositions. Definition of broad requirements, investigation of current data and processing.
The project is being identified and costs calculated. This stage is especially important as any omissions will have a bad effect on the whole project. Formulation of business systems requirements.
Evaluation of the implication and benefit of each proposed option. Identification of functional and non-functional require- ments in detail. Proposal of new methods and techniques in order to describe processing and data structures. Stage 4: Technical systems options: Definition and selection Maintenance of specific technical options, such as different methods of implementation.
Stage 5: Logical design: May be simultaneously to stage 4. User dialogues, update processes, enquiry processes are defined and selected. Stage 6: Physical design: After producing a physical design, creating a function and data design, the SSADM cycle is completed and the applications are ready for delivery. There is mainly one method that focuses especially on fast, flexible and low resources development of IS. IT uses prototyping to involve users, so this definitely meets their requirements, and can help to develop IS faster.
Its major principles are as follows:. The parts of organisational culture, on which SSADM, if applied, has an effect, are control, direction, risk tolerance, and communication patterns. So, an organisation with a structured and hierarchical culture, for example role or person culture, will have less problems adopting SSADM and getting its employees accustomed to it.
Whereas organisations with power or task cultures, which allow the single employee to take more responsibility, and which in general tend to be less bureaucratic and more dynamic, will have difficulties alongside the Structured Systems Analysis and Design Methodology.
And these are closely related to the stability of the business situation of the organisation. It can only profit from the advantages that SSADM provides, such as better quality due to the review of each stage or meeting the requirements more exactly due to emphasis on the requirements analysis stage , when the following criteria are met:.
First of all the volume and the time that is at disposal must be large enough to undergo the whole development process. Secondly, the short term business situation is not supposed to change drastically, because SSADM does not intend to change the specifications that were made in advance after the review of the stage had been completed.
This fact can lead to the problem that the end result deliver does not meet the business requirements at the point of time when it is delivered.
Considering the long-term situation, SSADM has shown that it increases the overall quality of Information Systems within an organisation. The fact that SSADM has become the imperative development methodology for government departments and their suppliers of IS proves this fact.
However, it must be considered that SSADM was developed especially for these kinds of companies and that government projects, in general, have enough time, money and human resources to cope with the bureaucratic nature of SSADM. It is said to be very bureaucratic, time and cost consuming.
Only for large organisations, such as government departments does it make sense to adopt this structured methodology. For medium-sized companies, developing a comparatively small information system, there are better solutions for developing an IS. Some discussion has been made about it in 3. But bearing in mind the limited resources of a medium-sized company, it should also consider using an off-the-shelf product, which is much less expensive and timeconsuming and has already been tested by various other companies.
Bocij, P. Hutchings, T. Krallmann, H. Robbins, S. P Organizational Behaviour: concepts, controversies and applications.
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Logical Data Modeling : The process of identifying, modeling and documenting the data requirements of the system being designed. Data Flow Modeling : The process of identifying, modeling and documenting how data moves around an information system. Save to Library.
SSADM is a waterfall method for the analysis and design of information systems. SSADM can be thought to represent a pinnacle of the rigorous document-led approach to system design, and contrasts with more contemporary agile methods such as DSDM or Scrum. SSADM is one particular implementation and builds on the work of different schools of structured analysis and development methods, such as Peter Checkland's soft systems methodology , Larry Constantine's structured design , Edward Yourdon's Yourdon Structured Method , Michael A. The SSADM method involves the application of a sequence of analysis, documentation and design tasks concerned with the following. In order to determine whether or not a given project is feasible, there must be some form of investigation into the goals and implications of the project.
ФБР имеет возможность прослушивать телефонные разговоры, но это вовсе не значит, что оно прослушивает. - Будь у них штат побольше, прослушивали. Сьюзан оставила это замечание без ответа. - У правительств должно быть право собирать информацию, в которой может содержаться угроза общественной безопасности. - Господи Иисусе! - шумно вздохнул Хейл. - Похоже, Стратмор здорово промыл тебе мозги.
Не двигайся! - приказал. На мгновение ей показалось, что на нее были устремлены горящие глаза Хейла, но прикосновение руки оказалось на удивление мягким. Это был Стратмор.
Но в общем хаосе их никто, похоже, не слышал. - Мы тонем! - крикнул кто-то из техников. ВР начала неистово мигать, когда ядро захлестнул черный поток.
И тогда он стал искать иные возможности. Так начал обретать форму второй план. Стратмор вдруг увидел шанс выиграть на двух фронтах сразу, осуществить две мечты, а не одну. В шесть тридцать в то утро он позвонил Дэвиду Беккеру. ГЛАВА 97 Фонтейн стремительно вбежал в комнату для заседаний.
Как прикажете это понимать. На лице Стратмора тут же появилось виноватое выражение. Он улыбнулся, стараясь ее успокоить.
- Почему он не звонит. Вода из горячей постепенно превратилась в теплую и, наконец, холодную. Она уже собиралась вылезать, как вдруг ожил радиотелефон.
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