Thursday, 11 July 2013

System Design

Systems design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements. Systems design could be seen as the application of systems theory to product development. There is some overlap with the disciplines of systems analysis, systems architecture and systems engineering.

 Detailed system design

Conceptual design in itself is not the end of the design process, rather it servers as a basis for the detailed MIS design. The performance requirements specified by the conceptual design become inputs to the detailed design phase, in which these are further refined, detailed and finalized to be called the system specifications.
          Thus, the main objective of the detailed system design is to prepare a blue print of a system that meets the goals of the conceptual system design requirements. Detailed system design involves the following phases.
  • Project planning and control.
  • Involve the user
  • Define the detailed sub-system.
  • Input/Output design.
  • Feedback form the user
  • Database design.
  • Procedure design.
  • Design Documentation
1) Project planning and control
In order to ensure an effective and efficient design of an MIS, it is very important that a detailed design process should in itself be considered a complete project. Therefore, the first step in the detailed design is planning and controlling, so that standards may be established and a proper follow-up is made. Some of the main points, which are important in planning and control of a detailed design, are given below.
Project planning
1.      Formulate the project objectives.
2.      Define the project tasks.
3.      Prepare a network diagram of all events and activities so as to specify sequential and parallel events.
4.      Schedule the work as per the requirements of the user.
5.      Prepare a budget for the project.
Project control
  • Get a feedback of the actual performance of the project with respect to time, cost and work of the project and compare it with schedules, budgets and technical plans.
  • Take corrective action where required so as to maintain control.
2) Involve the user
System designers must inform the user regarding the new information system being developed and gain their support and acceptance. In this phase, users are assured that changes will benefit them or that they will not be at disadvantage because of the new system.
3) Detailed sub system definition
In detailed system design, every system needs to be broken down to ascertain all activities required and their respective inputs and outputs. In some of the cases, sub systems are broadly defined in the conceptual design phase, but at this stage they are specifically defined to work out every detail concerning the sub-system. Decomposition of the system to operational activities in general is carried out as follows.
               Sub System
                       Functional component
                                    Sub Task
                                            Operation element
4) Output/Input Design
Having defined the subsystem well, by way of flow diagrams and a through discussion with the users of MIS, the system designers now define the specifications of outputs and inputs for each sub-system, in more detail. These specifications will later be used by programmers to develop programs to actually produce the output/input.
5) Feedback from the user
Having specifically defined sub-system, output and inputs, the designers once again involve the user to get feedback. This step will increase the acceptance of the MIS being designed. The system analyst should demonstrate the proposed MIS to the users of the system/sub-system. This step will also reassure the top management of the user organization that the detailed design project is processing as per plans.
1)      Database design
A database is an orderly arrangement of all the records related to each other. It servers as a data resource for the MIS of an organization. To have optimum performance, storage and fast retrieval of data, database design is an important phase in the detailed design of a system. For designing a database, the designer should keep the following points in mind.
  • Identify all data tables and record types.
  • Identify fields for each table, the key fields for each table and relations between various tables.
  • Determine the data type and width for each field of the tables.
  • Normalize the data tables.
  • Properly document data dictionary.
7) Procedure design
Procedures are the rules, standards or methods designed to increase the effectiveness of the information system. The procedures detail about the tasks to be performed in using the system. They serve as the ready recovers for the designers as well as for the users. Sometimes they perform the task of a supervisor over operators. There are a wide variety of procedures, which include:
  • Data entry procedures.
  • Run time procedures.
  • Error handling procedures.
  • Security and back up procedures.
  • Software documenting procedures.
In designing procedures, designers should:
  • Understand the purpose and quality standards of each procedures
  • Develop a step-by-step direction for each procedure, and
  • Document all the procedures.
8) Design Documentation
Detailed design starts with the performance specifications given by the conceptual design and ends with a set of design specifications for the construction of MIS. The outputs from the detailed design, i.e. design specifications, are handed over to the programmers for writing codes to translate system specifications into a physical MIS. Therefore, the system analyst should very carefully document the detailed design. In fact, design documents should consist of comprehensive details of all the design phases. Design documentation of detailed design report, generally, consists of
  • System objectives,
  • Design constraints,
  • Inputs/outputs,
  • Data files,
  • Procedures (manuals)
  • Proposed system (a summery and detailed flow charts),
  • Input/Output specifications,
  • Program specifications,
  • Database specifications,
  • Cost of installation and implementation, and
  • System test conditions.
 Design documents are a special type of CouchDB document that contains application code. Because it runs inside a database, the application API is highly structured. We’ve seen JavaScript views and other functions in the previous chapters. In this section, we’ll take a look at the function APIs, and talk about how functions in a design document are related within applications.


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