ISBN : 978-81-963532-2-3 (E-Book) Operation profile Different categories of users may use a software for different purposes. For example, a Librarianmightusethelibraryautomationsoftwaretocreatememberrecords,addbookstothelibrary,etc. whereas a library member might use to software to query about the availability of the book,or to issue and return books. Formally, the operation profile of a software can be defined as theprobability distribution of the input of an average user. If the input to a number of classes {Ci} isdivided, the probability value of a class represent the probability of an average user selecting hisnext input from this class. Thus, the operation profile assigns a probability value Pi to each inputclass Ci. Stepsin statisticaltesting Statistical testing allows one to concentrate on testing those parts of the system that are mostlikely to be used. The first step of statistical testing is to determine the operation profile of thesoftware. The next step is to generate a set of test data corresponding to the determined operationprofile.Thethirdstepistoapplythetestcasestothesoftwareandrecordthetimebetweeneach failure. After a statistically significant number of failures have been observed, the reliability canbecomputed. Advantagesanddisadvantagesofstatisticaltesting Statistical testing allows one to concentrate on testing parts of the system that are most likely tobe used. Therefore, it results in a system that the users to be more reliable (than actually it is!).Reliabilityestimationusingstatisticaltestingismoreaccuratecomparedtothoseofothermethods such as ROCOF, POFOD etc. But it is not easy to perform statistical testing properly.There is no simple and repeatable way of defining operation profiles. Also it is very muchcumbersome to generate test cases for statistical testing because the number of test cases withwhichthe system is to betested should bestatisticallysignificant. SOFTWAREMAINTENANCEPROCESSMODELS Two broad categories of process models for software maintenance can be proposed. The firstmodel is preferred for projects involving small reworks where the code is changed directly andthe changes are reflected in the relevant documents later. This maintenance process is graphicallypresented in fig. 25.1. In this approach, the project starts by gathering the requirements forchanges. The requirements are next analyzed to formulate the strategies to be adopted for codechange. At this stage, the association of at least a few members of the original development teamgoes a long way in reducing the cycle team, especially for projects involving unstructured andinadequately documented code. The availability of a working old system to the maintenanceengineers at the maintenance site greatly facilitates the task of the maintenance team 115 Software Engineering Keerthana P, Manasa KN, Ganga D Bengal
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