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Unformatted text preview: 9-1 9.0 OPERATIONAL PROFILESSimilar to hardware, software performance is significantly dependent on the environment in which it operates. The similarity ends there. With hardware, the environment physically changes a piece of equipment. This physical change is mainly responsible for faulty behavior. A software system doesnt change, but can still fail due to the inputs it receives from the external environment. The reliability of a software-based product depends on how the computer and other external elements will use it1. Making a good reliability estimate depends on testing the product as if it were in the field. The operational profile(OP), a quantitative characterization of how the software will be used, is therefore essential in any Software Reliability Engineering (SRE) application. It is a fundamental concept which must be understood in order to apply SRE effectively and with any degree of validity. This section provides a detailed description of the OP. A profileis a set of independent possibilities called elements, and their associated probability of occurrence. If operation Aoccurs 60 percent of the time, Boccurs 30 percent, and Coccurs 10 percent, for example, the profile is [A, 0.6...B, 0.3...C, 0.1]. The operationalprofile is the set of independent operations that a software system performs and their associated probabilities. Developing an operational profile for a system involves one or more of the following five steps: 1. Find the customer profile 2. Establish the user profile 3. Define the system-mode profile 4. Determine the functional profile 5. Determine the operational profile itself The process for developing the operational profile is depicted in Figure 9-1. CustomerProfileUser ProfileSystem-modeProfileFunctional Profile# Functions , Environ. VariablesInitial List , Final Function ListExplict/Imp. , Occurrence Probs. Divide Exec. into runs , Partition input space Identify input space , Occurrence ProbabilitiesOperational ProfileTest SelectionFIGURE 9-1. Operational Profile Development21Musa, John D;Iannino, A.; Okumoto, K; Software Reliability Measurement, Prediction, Application, McGraw-Hill, 1987. 2Musa, J.D., Operational Profiles in Software Reliability Engineering, IEEE Software Magazine, March 1993, 9-2 9.1 Customer Profile. A customer is the individual, group or organization that is purchasing the software system, the same as any other product. A customer profileconsists of an array of independent customer types. A customer typeis one or more customers in a group that intend to use the system in a relatively similar manner, and in a substantially different manner from other customer types. An example of a software system with different customer types would be a spreadsheet package....
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- Spring '11