Systems analysis and design /Alan Dennis, Barbara Haley Wixom, Roberta M. Incorporation of Object-Oriented Concepts and Techniques. JeHrey L. Whitten Professor)>::J Lonnie D. Bentley Professor 0 - Both at Purdue University West Lafayette, IN - · U> With contributions by 0 GaryRandolp?. Welcome to the domain of system analysis, design, and development or, in the design, and development methods from the bottom up over a period of 10 to
|Language:||English, Spanish, German|
|Genre:||Children & Youth|
|ePub File Size:||18.44 MB|
|PDF File Size:||9.72 MB|
|Distribution:||Free* [*Sign up for free]|
Get this from a library! Systems analysis and design methods. [Jeffrey L Whitten; Lonnie D Bentley]. Today's students want to practice the application of concepts. As with the previous editions of this book, the authors write to balance the coverage of concepts. Systems analysis and design methºds / Jeffrey L. Whitten, Lºnnie D. Systems Analysis and Design Methods, seventh edition, is intended to support one or.
Personal information is secured with SSL technology. Free Shipping No minimum order. Table of Contents 1. Water quality in industrial systems. Geochemical source of pollution. Effect of evaporation on concentrations. Effects of poor quality water.
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.
Introduction 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. 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. 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. 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.
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.
The following graphic shows the symbols that are used to produce a DFD. Abbildung in dieser Leseprobe nicht enthalten 3.
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. This information is put down in a so called Entity Life Histories16 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. Water quality in industrial systems. Geochemical source of pollution. Effect of evaporation on concentrations. Effects of poor quality water. Oil emulsion breakdown. Potable water standards. Agriculture and irrigation. Mathematical modelling of water quality. Mass balances.
Mixed and plug flow systems. Systems analysis. Terminal concentration in a water circuit. Application to a mine water circuit. Computer simulation model. Non conservative parameters. Basic mass balance equation.
Oxygen balance in rivers. Calibration of a moving BOD model. Oxygen balance. Field measurements. Numerical methods. Simulation of hydraulic systems. Numerical methods for the solution of single differential equations. Finite elements. Mass balance of stormwater pollutants.
Catchment description. Quality observations. Mass balance for event of 18 January on Hillbrow catchment. Mass balance for event of 7 March on Montgomery Park catchment. Optimum allocation of water resources subject to quality constraints. The system. Solution method. Linear programming solution. The linear programming technique with separable programming applied.
Economics of desalination of wastewaters. Alternatives for optimal reuse of waste water.
Selection of optimum desalination methods. Relevant desalination methods. Cost analysis. Computer analysis justifies desalination.