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Part III System Analysis and Design; Programming

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- Decision Support Systems
- Pictorial Model
- Tools: Excel, VBA, IFPS
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- Supports Decisions
- Must identify decision criteria (e.g., balance in check writing)
- “Functions” for most frequently used (significant few) tools
- Programming tools for “trivial many” customization

- Modeling (1.2) (Transformation Function, what is it? what are the significances of using this term?)

- Consists of Pictorial Diagram and equations (pp. 2-3, 5-2)
- Uses numbers to identify equations and their sequence
- The number of lines out of an attribute indicates its influence to the entire model.

- Boundary variables have no predecessor
- Boundary variables will become “assumptions” in IFPS programs

- Quick solution; ready-to-use functions (e.g., pmt, stdevp)
- Once set up, users can change input parameters (e.g., interest rate, loan amount) to “reuse” this “program”
- Not as flexible but less knowledge in programming is needed.

- For any programming language, must know “input” and “output” first
- All programs can be broken down to sequential, iterative (loops), and selection (if-then)
- VBA uses spreadsheet as the source of data (input) and display of results (output) -- see handouts

- More flexible (e.g., length of annuity table does not have to be pre-determined)
- Programming idiosyncrasies (e.g., ‘=‘ means assign and not equal)
- Most fundamental functions: a=a+1 (counter) and sum=sum+a
- for-next loop and if-then-else (see handouts)

- For Logical Design step, research the process by reading books (document) and look for formula (form)
- Definitional Formula is easier to understand (why?)
- Computational Formula is more efficient (why?)

- 4GL (see 1.3 and 1.6)
- Extract equations (i.e., business model) from descriptions
- Organize the pictorial diagram starting with the goal (e.g., profit) and work backwards
- Once the pictorial model is done, the IFPS program is basically done as well.

- Compared to Excel, IFPS can do what-if analysis (manipulate input variables) as well
- Goal seeking allows user to pre-determine the outcome and view the possible choice of input variables
- Simple graphics and report generation for final decision making

- Direction and Magnitude (slope of a curve, coefficient for regression line)
- Graphics allow a quick view of the long-term trend
- Knowledge of the attributes is more important than the knowledge of the tools
- Knowledge of the tool enhances the ability to analyze

- “Right” is subjective
- Easy-to-use modeling tool (compared to Excel and VBA) allows the management to move into Physical Design and Implementation/ Testing stage (End-user development in Laudon chapter 11, p. 349)