Page 65 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Unit 3: Software Requirements

Standards Compliance Notes
This specifies the requirements for the standards the system must follow. The standards may
include the report format and accounting procedures. There may be audit requirements which
may require logging of operations.

Hardware Limitations
The software may have to operate on some existing or predetermined hardware, thus imposing
restrictions on the design. Hardware limitations can include the type of machines to be used,
operating system available on the system, languages supported, and limits on primary and
secondary storage. Reliability and Fault Tolerance: Fault Tolerance requirements can place a
major constraint on how the system is to be designed, as they make the system more complex
and expensive. Recovery requirements are often an integral part here, detailing what the system
should do if some failure occurs to ensure certain properties.
3.5.5 Specification Language
A requirements requirement for an in order system is important for several reasons; it serves as
a means of communication between the consumer and the systems developer. it represents in a
systematic fashion the present state of the real world, its problems and its future requirements;
it enables the systems developer to turn real world problems into other forms which are more
manageable in terms of size, complexity, human understanding and computer process ability; it
serves as the basis for the design, implementation, testing and maintenance of the target system.
In order that all the objectives of a requirements specification are met, we need a powerful
specification language. Information systems development can be conceived of as an engineering
process. We must first of all build a model, which is a small-scaled abstract representation of the
real world. All unnecessary details in the physical world which are irrelevant to the engineering
process are removed from the model, or in other words, ignored during the analysis stage. When
a bridge or tunnel is planned between two nations, for instance, the political issues should best
be dealt with by politicians and not form part of the engineer’s requirements specification. If the
resulting model is still too complex, further abstractions may be necessary, until the problem
is reduced to a manageable size. The model is then analyzed and manipulated until a feasible
solution is found. In engineering, diagrams and mathematics are often used because they have e
been found to be more suitable for manipulation than verbal descriptions. One representation may
have to be transformed into another so that the most appropriate model for a given analysis can
be used. Diagrams, for instance, may have to be converted into equations. Finally, if the abstract
solution is accepted by the customer, a construction phase turns it into a real system. In order
for a requirements specification to be useful in systems. In order for a requirements specification
to be useful in systems development, seen as an engineering process, the specification language
must exhibit various features, each being relevant to one of the stages. These features will be
highlighted in this section. We recognize that there are authors who may object to having an
engineer’s view of information systems development. Understanding the impacts of change,
people-oriented design and user participation throughout the development process. It would
be interesting to study how our proposal for the desirable features of a specification language
fits into this alternative framework.
3.5.6 Structure of Document

Design document structures so that the dissimilar parts are as self-governing as possible. This
allows each part to be read as a single item and reduces problems of cross-referencing when
changes have to be made. Structuring a document properly also allows readers to find in sequence
more easily. As well as document components such as contents lists and indexes, well-structured
documents can be skim read so that readers can quickly locate sections or sub-sections that are
of most interest to them. Structure of a document should include the components the standard

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