03-03-ReqSpecificationStyles-operational-notes

03-03-ReqSpecificationStyles-operational-notes -...

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1 CSE 435: Software Engineering B. Cheng Foundations of specification Part I: The operational style Topics: – Notations and methods for writing specifications – Examples of operational notations • Data flow diagrams (highlighted) • State diagrams • Petri nets CSE 435: Software Engineering B. Cheng Specification qualities Precise, clear, unambiguous Consistent Complete – internal completeness – external completeness Incremental – helpful during analysis if one can make a “first cut” and then incrementally refine – document is structured; can be understood in increments CSE 435: Software Engineering B. Cheng Specification styles Degree of formality: – Formal specification: • is a mathematical entity • process for constructing is grounded in mathematics – Informal specification: • less rigorous, but often more amenable to visualization • e.g., UML diagrams Operational: – Behavior specification in terms of some abstract machine Descriptive – Behavior described in terms of properties
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2 CSE 435: Software Engineering B. Cheng Example: Operational specification of an ellipse Ellipse is a geometric figure that can be drawn as follows: 1. Select two points P1 and P2 on a plane 2. Get a string of a certain length and fix its ends to P1 and P2 3. Position a pencil as shown in next figure 4. Move the pen clockwise, keeping the string tightly stretched, until you reach the point where you started drawing Note: Slide adapted from Ghezzi, Jazayeri, and Mandrioli !! CSE 435: Software Engineering B. Cheng Implementing the specification of a ellipse Note: Slide adapted from Ghezzi, Jazayeri, and Mandrioli !! CSE 435: Software Engineering
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03-03-ReqSpecificationStyles-operational-notes -...

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