Requirements Analysis for information system:
User should recognize the needs for system change. Analyst identifies and verifies such needs using suitable methods and tools . One has to know the problem to be solved before thinking in any solution . In doing so, he defines the impetus for system change, its sources and ideas. Systems change can be generated from within the system (organization based), or comes from outside (environment based).
Organization based as:
  1. Organization itself:
  2. Any change in organizational structure or processing functions will impact the information flow and the processing functions of the organization, which requires redesign of the processing model.
  3. Top management:
  4. Top management may initiate the change by introducing new process or policy, or even change the corporate strategy.
  5. System users:
  6. System users (either computer system users or employees) may initiate the change in search for faster processing, or more efficient functions
  7. Systems analyst:
  8. System analyst can suggest change based on his analysis or in order to satisfy corporate objectives.
Environmental based as:
  1. Change government rules and regulations:
  2. Imposing new rules and regulations requires reformulation of corporate or organization policy and procedures
  3. Customers:
  4. Changing consumers habit or mode will require re-evaluation of company production rules or even the review of the product itself.
  5. Union:
  6. Union may impose new rules on labor law or benefit which force the organization to introduce change or initiate a system study.
  7. Competition:
  8. New competitors or change of existing competitor ability may for a threat to the market share of the organization.
All these sources may force the company or organization to initiate a system change study. This study should be done and led by a qualified person (systems analyst), and should go through number of stages or phases starting from defining the problem up to implement the change. In the first phase of system development analyst should answer a very important question "what is the problem?" through an initial investigation study. The objective is to define true needs of systems change and clearly define the problem, and look for possible alternative answers for key problem issues. This analysis should ends up with requirements definitions which lead to system speceification document. This document is used to define software requirements definition which becomes a base for software requirements analysis
Software requirement analysis:
Introducing new software applications into the organization requires new system study or system change. This change may include the software application to suite the new organization process or change the organization to comply with the application processing. In both cases system study with clear identification of software requirements is required.
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The two approaches of software development:

The two graphs show software development approaches
based on the starting stage either
from the information system change,
or from the need of introducing a software.

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System Analysis and Design:
System analysis and design are concerned with the investigation of an organization and the design and implementation of a computerized solution to that organization needs. To analyze a system is to identify its components (devices, people, rules and procedures) and their interrelationships in order to determine its objectives, requirements, and priorities. The analyst must find ways of representing organization as a whole system, taking into consideration any economic behavioral and technical constraints. To know more about systems analyst job from the internet click here. and visit the international institute of business analysis(IIBa).