What Is The Data Flow Model About The Designing Of A Software?

DATA FLOW MODEL:
In a data flow model, functional transformation processes their inputs and produce outputs. Data flows from one to another and is transformed as it moves through the sequence. Each processing step is implemented as a transform. Input data flows through these transforms until converted to output. The transformation may execute sequentially or in parallel. The data can be processed by each transform item by item or in a single batch.
When transformations are represented as separate process, this model is sometimes called the "PIPE AND FILTER MODEL" after the terminology used in the UNIX system. Unix system provides pipes which acts as data conduits and a set of commands which are functional transformations. Systems which conform to this model can be implemented by combining Unix commands using pipes and the control facilities of the UNIX shell. The term "filter" is used because a transformation filters out  the data it can  process from its input data stream.
Variants of this data flow model have been in use since computers were first used for automatic data processing. When transformations are sequential with data processed in batches, this architectural model is a batch sequential model.
This model supports the reuse of transformations.

REQUIREMENTS ELICITATION AND ANALYSIS


Elicitation and analysis is a difficult process for a number of reasons:-


1-Stakeholders often don't really know what they want from the computer system except in the most general term; they may find it difficult to articulate what they want from the system; they may take unrealistic demands because they are unaware of the cost of their requests.

2-Stakeholders in a system naturally express requirements in their own terms and with implicit knowledge of their own work. Requirements engineers, without experience in the customer's domain, must understand these requirements.

3-Different stakeholders have different requirements and they may express these in different ways. Requirements engineers have to discover all potential sources of requirements and discover commonalities and conflicts.

4-Potential factors may influence the requirements of the system. These may come from managers who demand specific system requirements because these allow them to increase their influence in the organization.

5-The economic and business environment in which the analysis takes place is dynamic. It inevitably changes during the analysis process.  Hence the importance of particular requirements may change. New requirements may emerge from new stakeholders who were not originally consulted.