Due to various types of description methods, checks of consistence cannot be carried out. Especially with large systems, the outline diagram can become very unclear, because all relevant data flows have to be included. This symbol added later. Name should represent the process. Process and data flow names have the first letter capitalized.
Also note that the Offered Course file is still preserved. Program logic helps to attain precision while natural language helps in getting the convenience of spoken languages. Estimated budget Here, the various options are identified in terms of costs and benefits 2. Physical requirements and 3. DFDs for the selected option. Costs One time cost Recurring Cost 1. Cost of converting from present system to proposed system. Construction or remodeling of existing facilities.
Hardware cost. Salary of personnel 2. Supplies 3. Equipment maintenance. Benefits Tangible Benefits Intangible Benefits 1. Reduction 1. Customer in cost of satisfaction operation. Better 2. Increased employee value in morale sales and due to net income.
Reduced time facilities. Better company image. Satisfaction to management about entering into newer information technologies The life span of the new system has to be decided by taking into consideration Net Present Value and Internal Rate of Return of the future cost benefits.
The output of this subprocess will be the cost benefit analysis report which will serve as the input for subprocess 2. In this subprocess, the most important activity of taking the decision of selecting the best option is carried out. This selection outlines the hardware and software requirements. The final result of this is the structured specifications which consists of an interpreted set of DFDs, DDs and process descriptions.
Step 3 : Structured Design Structured Design is a data-flow based methodology. The input for structured design is structured specifications which is the output of structured analysis. It also receives input from the hardware study. Step 4 What we do in the system design process is to convert the logical design specifications i. In short, system design involves transforming a logical design into a physical design. This step is much more exacting than designing logical design specifications.
The Software Packaging includes 1. Input-output design 2. Files and Database design 3. Program design and 4. Control Design Activities that run parallel to this detailed design steps of software packaging are 1.
Equipment specifications 2. Test specifications and 3. User interface specifications In fact, these parallel activities have their roots in structured analysis part. Here we refine and expand their specifications to make each one as concrete as possible. The process 3 in figure 4. This is essential to divide the total design process into smaller independent modules which in turn help to have flexibility in the design, i.
Hence this technique provides a top-down, flexible design which is easier to maintain. To maintain a dialogue with users during the process of system design is often difficult. Wise designers make it a point to involve users at several stages in the design and more particularly in the earlier stages of the design itself.
For this, they use a technique called Structured Walk through. A Structured Walk through is an organized step by step tracing through of a design by a group of people. The group may be peer group or users. The purpose of Walk through is to find where improvement can be made in the system or in the development process. There are two types of Structured Walk throughs 1. A Preliminary Design Walk through 2. Walkthroughs are conducted 1. To catch design errors in advance 2.
To improve communication and 3. To do this, we need to construct what is called Structured charts. A Structured chart is a documentation technique. It shows the hierarchy of modules and their interrelationships in a program or a system. While a DFD considers a sequential order of processes the structured chart begins with the most important process BOSS and then goes on to its subordinate processes. It was accepted as the national standard of Great Britain for information systems development in Thus SSADM usage is expedient for those who work with governmental organizations as this method is a standard for these organizations.
SSADM is based on the data flow diagrams. At the early stages of projecting at description of models functional, informational and event-trigger the top-down method is used. At the description of data flows out of the system and into the system DFD, which denote boundaries of the system, are used.
LDS describes which data the system operates with. It is created for existing system and is added at the development of the new one. These diagrams support states indications and the possibility of description not only consecutive but parallel or reiterative events and also description of the choice of events course.
ELN describes how data change in the system in the course of time at different variants of events. Analysis, projecting and documenting of information system accordingly to SSADM involves 6 main stages.
Each stage is divided into several steps, which define tasks that should be fulfilled at the given stage. The system is studied for getting system requirements. Detailed project is created on the logic level and then transformed into physical project. It involves the analysis of the existing system and creation of DFD for visualization of known problems and system description.
If the system is developed from the beginning than the projecting starts from definition of new system requirements. Requirements definition. On the basis of available data about the system new functions, which the system must execute are defined.
Also boundaries of the future system and data which will be processed by the system are defined. Infological model of requirements is constructed. Definition of technical requirements and device equipment cost.
Definition of the expected profit with the introduction of new functions. Development of logical data model.
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