Recall The Team SkillsChapter 24 Technical Methods for Specifying RequirementsIntroductionTechnical Specification MethodsPseudo-codeExample of Pseudo-codeFinite State MachinesSlide 8Decision Tables and Decision TreesActivity DiagramsSlide 11Entity-Relationship ModelsKey PointsRecall The Team Skills1. Analyzing the Problem (with 5 steps)2. Understanding User and Stakeholder Needs3. Defining the System4. Managing Scope5. Refining the System Definition1. Software Requirements: a more rigorous look2. Refining the Use cases3. Developing the Supplementary Specification4. On Ambiguity and Specificity5. Technical Methods for Specifying Requirements6. Building the Right SystemChapter 24Technical Methods for Specifying Requirements Pseudo-code Finite state machines Decision tables and decision trees Activity diagrams (flowcharts) Entity-relationship modelsIntroductionThere are cases in which the ambiguity of natural language is simply not tolerableExamples: when the requirements deal with life-and-death issues or when the erroneous behavior of a system could have extreme financial or legal consequences.If the description of the requirement is too complex for natural language and if you cannot afford to have the specification misunderstood, you should consider writing or augmenting that portion of the requirements set with a "technical methods" approach.Technical Specification Methods Pseudo-codeFinite state machinesDecision tables and decision treesActivity diagrams (flowcharts)Entity-relationship models…Pseudo-codePseudo-code is a "quasi" programming language An attempt to combine the informality of natural language with the strict syntax and control structures of a programming language. It usually consists of combinations of: Imperative sentences with a single verb and a single objectA limited set, typically not more than 40–50, of "action-oriented" verbs from which the sentences must be constructedDecisions represented with a formal IF-ELSE-ENDIF structureIterative activities represented with DO-WHILE or FOR-NEXT structuresExample of Pseudo-code A pseudo-code specification of an algorithm for calculating deferred-service revenue earned for any month is:Set Sum(x)=0 FOR each customer X IF customer purchased paid support AND ((Current month) >= (2 months after ship date))AND ((Current month) <= (14 months after ship date))THEN Sum(X)=Sum(X) + (amount customer paid)/12ENDFinite State MachinesExample of a state transition diagramThe natural language expression "the other light shall flash every 1 second" was ambiguous. The above state transition diagram is not ambiguous since it illustrates that duty cycle B was indeed the right choice.Finite State MachinesExample of a State Transition Matrix for an On/Off Counting Device:What happens if the user presses the On switch and the device is already on? Answer: Nothing.What happens if both bulbs are burned out? Answer: The device powers itself off.Decision Tables and Decision Trees It's common to see a requirement that deals with a combination of inputs; different combinations of those inputs lead to different behaviors or outputs.Activity DiagramsAn activity diagram is essentially a flowchart, showing flow of control from activity to activity.Entity-Relationship Models If the requirements within a set involve a description of the structure and relationships among data within the system, it's often convenient to represent that information in an entity-relationship diagram (ERD).Key PointsTechnical methods for specifying requirements are appropriate when the requirement description is too complex for natural language or if you cannot afford to have the specification misunderstood.Technical methods include pseudo-code, finite state machines, decision trees, activity diagrams, entity-relationship models, and many
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