Block 3 Unit 10 Flashcards
Suggest three expectations that a customer might have of a software product without perhaps being aware of them.
Three possibilities are:
the product will not conflict with other software that they use
the product will boost productivity
the product will be simple to use
Explain how increasing integrity within a system could affect efficiency.
Increasing integrity within a system means strengthening measures to ensure that modification or deletion of data by unauthorised persons, or by any other unintended means, does not occur. This might involve the use of passwords to access certain data and an authentication server to check a user’s identity, or it might mean that network traffic needs to be encrypted and decrypted. Each of these factors adds an overhead to processing, so efficiency is likely to be reduced
Identify one other pair of SQFs that are not independent.
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Another pair of SQFs that are not independent is usability and portability. For example, many of the features of the Apple Macintosh that contribute to its reputation for usability are built into its operating system. Applications that take advantage of these features are less portable to other systems, such as Windows or Linux.
verification of a system involves two tasks:
ensuring that all system descriptions are self-consistent
ensuring that all system descriptions are consistent and complete with respect to those from which they were derived.
validation comprises:
ensuring that all system descriptions are consistent with the customer’s requirements, including implicit requirements.
Give a simple example of two system descriptions that might contradict each other.
There are numerous possibilities. One elementary example would be if a structural model for a hotel reservation system indicated that a reservation could be made for more that one room but the implementation only allowed one room per reservation.
Why is it important for the customer’s requirements statement to be self consistent?
If the customer’s requirement statement lacks self consistency, then either the resulting system will be inconsistent or it will not satisfy the customer’s requirements. The system builders can decide (implicitly or explicitly) how to resolve the inconsistencies or, if the inconsistent requirements affect different parts of the system and are not picked up by the developers, the developers could inadvertently build the inconsistencies into the product.
Give two reasons why it is useful to run a unit test before the relevant code increment has been written
a. If the test unexpectedly already passes at this point, this demonstrates that it is not a good test of the next increment.
b. If it fails in an unexpected way, this demonstrates a faulty or incomplete understanding of the test that needs to be addressed in order to have a good grip on the code and test
