180 likes | 446 Views
System Analysis and Design. System Analysis. - Mr. Ahmad Al-Ghoul. Learning Objectives. Understand the purpose and goals of producing process description Discuss and understand the modular design Use structured English to analyze and describe processes. Process Description Tools.
E N D
System Analysis and Design System Analysis - Mr. Ahmad Al-Ghoul
Learning Objectives • Understand the purpose and goals of producing process description • Discuss and understand the modular design • Use structured English to analyze and describe processes System Analysis and Design System Analysis
Process Description Tools • A process description or specification • documents the details of a functional primitive, which represents a specific set of processing steps and business logic • Process description link the process to the DFD and the data dictionary. • Process description can be represented in a variety of tools, the most popular are: • Structured English • Decision Tables • Decision Trees [2] System Analysis and Design System Analysis
Process Description Tools • The goals of producing process description are • Reduce process ambiguity • Obtain a precise description of what is accomplished • Validate the system design, including data flow diagrams and the data dictionary System Analysis and Design System Analysis
Process Description Tools Process specifications are not created for: • Physical input and/or output processes, such as read and write. • Processes that represent simple data validation. • Processes for which prewritten code. These processes are generally included in a system as subprograms and functions. System Analysis and Design System Analysis
Process Description Tools • Modular Design • Based on combinations of three logical structures, sometimes called control structures which serve as building blocks for the process • Each logical structure must have a single entry and exit point • In modular design a rectangle represents a step or process, diamond shape represents lines in the direction indicated by the arrows • Three structures • Sequence • Selection • Iteration - looping System Analysis and Design System Analysis
Process Description Tools • Modular Design • Sequence • The completion of steps in sequential order, one after anther [1] System Analysis and Design System Analysis
Process Description Tools • Modular Design • Selection • describe a series of alternative policies from which only one is selected. Represented by IF <condition> CASE <statement> WHEN <condition> <statements> ELSE WHEN <condition> <statements> <statement> … ……….. …... [1] System Analysis and Design System Analysis
Process Description Tools • Modular Design • Iteration – looping • A policy or series of actions is repeated until a specific condition changes. Represented by DO…WHILE construct or a REPEAT … UNTIL construct [1] System Analysis and Design System Analysis
Process Description Tools Structured English • Structured English is based on structured logic and Simple English statements • Modified form of English used to specify the logic of information processes • Uses a subset of English • Action verbs • Noun phrases • No adjectives or adverbs • No specific standards, Standards vary between organisations • Must conform to the following rules • Use only the three building blocks of sequence, selection, and iteration • Use indentation for readability • Use a limited vocabulary, including standard terms used in the data dictionary and specific words that describe the processing rules System Analysis and Design System Analysis
Process Description Tools Structured English Example • The VERIFY ORDER process description includes logical rules and a structured English version of the policy. Notice the alignment and indentation of the logic statements. [1] System Analysis and Design System Analysis
Process Description Tools Structured English Example • Sample of a policy with logical rules, and a structured English version of the policy. Notice the alignment and indentation of the logic statements. [1] System Analysis and Design System Analysis
Process Description Tools • Data Dictionary and Structured English The data dictionary is a starting point for creating structured English: • Sequenced data dictionary entries become simple structured English statements. • Selection [] entries become IF..THEN...ELSE statements. • Iteration { } entries become DO WHILE, DO UNTIL, or PERFORM UNTIL structured English statements. System Analysis and Design System Analysis
Process Description Tools Structured English Advantages: • consice and precise, allow easy reading without ambiguity & misunderstanding • language notation may be tailored to suit user • must exist a cross-referencing with any DFD & DD entries thus perimitting thourough verification Disadvantages: • formality may be alien when first read or write • Avoid assuming that anything written in SE is correct System Analysis and Design System Analysis
Sequence Summary • Modular Design based on combinations of three logical structures, sometimes called control structures which serve as building blocks for the process • Three structures, sequence, selection, and iteration – looping • Structured English uses a subset of standard English that defines each process with combinations of the basic building blocks of sequence, selection, and iteration System Analysis and Design System Analysis
Sequence Summary • In this Sequence we have • Explained the modular design and its three logical structures, sometimes called control structures which serve as building blocks for the process • Defined and described the three structures, sequence, selection, and iteration – looping • Explained how to use structured English to analyze and describe processes • Explained the advantages and disadvantages foe structured English System Analysis and Design System Analysis
Reference [1] System Analysis and Design, Sixth Edition Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt , Publisher: SHELLY CASHMAN SEWIES. [2] system analysis and design, sixth edition Authors: Kenneth E. Kendall and Julie E. Kendall Publisher: Prentice Hall [3] Modern Systems Analysis and Design Third Edition Authors: Jeffrey A. Hoffer , Joey F. George, Joseph S. Valacich Publisher: prentice hall [4] System Analysis and Design, 3rd Edition Authors: Dennis, Wixom, & Roth Publisher: John Wiley & sons System Analysis and Design System Analysis