Design Method -2

The Data design is the 1st and some would say the most important of 4 design activities which are conducted in during software engineering.The collision of    data structure on program structure,    procedural complexity causes data design to have a profound influence on software excellence. The concepts of data abstraction and information hiding give the foundation for an approach to data design.

An important related activity in during of design is to   recognize those program modules which must operate directly upon the logical data structures.   By this way the scope of effect of individual data design decisions can be constrained.Regardless of the design methods to be used well designed data can lead to better program modularity and structure and reduced procedural complexity.

The Wasserman has proposed a collection of principles which may be used to design and specify data.  In reality, the design of data starts during the establishment of the analysis model.  By Recalling that design and requirements analysis often overlap we consider the following collection of principles [WAS80] for data specification:

1.    The Systematic analysis principles useful to behavior and function should also be applied to data.  We spend much effort and time reviewing, deriving and specifying functional needs and preliminary design. The Representations of data relationships, objects, dataflow and content should also be established and reviewed alternative data organizations should be considered and the impact of data modeling on software design should be evaluated.   Example for specification of multilinked list may nicely satisfy data needs but may lead to an unwieldy software design.  The alternative data organization may lead to better results.

2.    All the operations and data structures to be performed on each should be recognized. The design of an efficient data structure must take the operations to be performed on the data structure must take the operations to be performed on the data structure into account. Example for let’s consider a data structure made up of a collection of diverse data elements.  Data structure is to be manipulated in a number of main software functions.  It’s upon evaluation of the operation performed on the data structure an abstract data type is described for use in subsequent software design. The specification of the abstract data type may easy software design considerable.

3.    The data   dictionary should be building and used to describe both program design and data.   The concept of a data dictionary was introduced in further chapters. A data dictionary explicitly represents the relationships between the constraints and data objects on the parts of a data structure. The Algorithms which must take advantage of exact relationships can be more simply described if a dictionary like data specification exists.