August 1, 2015 1 August 1, 2015August 1, 2015August 1, 2015 Azusa, CA Sheldon X. Liang Ph. D....

April 19, 20231

April 19, 2023April 19, 2023 Azusa, CAAzusa, CA

Sheldon X. Liang Ph. D.

Software Engineering Software Engineering in CS in CS at at APUAPU

Azusa Pacific University, Azusa, CA 91702, Tel: (800) 825-5278 Department of Computer Science, http://www.apu.edu/clas/computerscience/

CS 470 Software Engineering ICS 470 Software Engineering I

http://www.apu.edu/clas/computerscience/

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CS 470 Classical AnalysisCS 470 Classical Analysis


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Systems Analysis:

1. What to do: the evaluation of an activity to identify its desired objectives and determine procedures for efficiently attaining them.

2. What needed: the methodical study of the data-processing needs of a business or department, together with recommendations for specific hardware and software installations.


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Role of the Analyst

• The analyst is the liaison between the user and the development team.

• His final product must be understandable to the users and the developers.

• He doesn’t tell the developers how to create the product, just what it should do in a very exacting manner.


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The Goal of Analysis

• The most important product of systems analysis – is the specification document.” - DeMarco

– Informal enough for the client

• The client is generally not a computer specialist

– Formal enough for the developers

• It is the sole source of information for drawing up the design


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Specification Document

• The specification document is the final product of the systems analyst

• It is a contract between the client and the developer

• Specifies what the product must do and the constraints on the product


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Methods of Analysis

• Demarco(1979) – Data Flow Diagram

– Data Dictionary

– Structured English

– Decision Tables

– Decision Trees


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Structured Systems Analysis

• The analysts job:

– What business functions should she computerize?

• Accounts payable

• Accounts receivable

• Inventory

– What equipment will they need?

– How much are they willing to spend?

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• The data flow diagram (DFD) shows the logical data flow – “What happens, not how it happens”

• First refinement– Infinite number of possible interpretations

Step 1. Draw the DFD

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• Second refinement– PENDING ORDERS is scanned daily

Step 1. Draw the DFD

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CS 470 Classical AnalysisCS 470 Classical AnalysisStep 1. Draw the DFD

• Portion of third refinement

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Step 2. Decide What Parts to Computerize and How• It depends on how much client is prepared to

spend

• Large volumes, tight controls– Batch

• Small volumes, in-house microcomputer– Online

• Cost/benefit analysis

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CS 470 Classical AnalysisCS 470 Classical AnalysisStep 3. Determine the Details of the Data Flows

• Determine the data items for each data flow• Refine each flow stepwise• We need a data dictionary for larger products

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Structured Systems Analysis

• Response times cannot be determined• The number of I/O channels can only be guessed• CPU size and timing can only be guessed• Nevertheless, no other method provides these data for

arbitrary products

Overall• The method of Gane and Sarsen/De Marco/ Yourdon has

resulted in major improvements in the software industry

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Take a look at my research

Thank you very much!

Questions?

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