1. Spreadsheet-Based Decision Support Systems Chapter 22:
The DSS Development Process
Aslı Sencer
MIS 463

2. Defining the DSS Development Process
Now that we have discussed in great detail the components of a spreadsheet-based decision support system (DSS), we need to learn the process of putting these components together to build a complete DSS application.
We propose six basic steps for developing a DSS:
Application Overview: Welcome sheet, input, model and calculations, output, resolve
Worksheets: Welcome sheet, input sheet, calculations sheet, output sheet
User Interface: Navigational buttons, receiving input, functional buttons
Procedures: Receiving input, model and calculations, output analysis and display, navigational
Resolve Options:
Testing and Final Packaging

3. STEP 1: Application Overview
Most important step in DSS development!
Create a layout of the entire application to understand the flow from the user input to the model calculations to the output
Welcome Sheet: Flow begins; introduction to what DSS is and how to begin using it.
Input:
Type of input: sheet, forms, or input box.
Model and Calculations:
Formulation of objectives and necessary input; Type of model: Performing an optimization, or running a simulation. Formulations and functions: Calculate by Excel or dynamically in code
Output: A driving force in why the users are using the DSS.
Type of output: Charts, graphs, histograms, tables Ask: Is it necessary to redisplay some inputs? Is the the output adequate?
Re-solve Options: Resolve options; modify input; redefine constraints or objectives.

4. STEP 2: Worksheets Design
How many sheets will be used, with which features? Use mostly Excel features; use VBA for more complicated, dynamic tasks! Worksheet design should be completed before code-based interface!
Welcome Sheet
Input Sheet
Model and Calculation Sheets
Output Sheet

5. STEP 2: Worksheets Design
Welcome Sheet:
Title and description of the DSS
Assumptions, source of model formulation, images, photos
“Start” button

6. STEP 2: Worksheets Design
User input to the worksheet
2. Input Sheet:
User input/Large data input/may be combined with other sheets
If not use a sheet for input, may use a form or input box
Appropriate labels, input locations
Input calculations and output are on the same worksheet
Large data imported from a text file or database

7. STEP 2: Worksheets Design
3. Calculations Sheet:
Spreadsheet calculations by a solver
Simulation results
Usually hidden from user: user is not familiar with the details, only interested in results. Might be optional to view.

8. STEP 2: Worksheets Design
Dave's Candies Simulation
Simulation Model
Simulation Results
Trial
Demand
Profit
Bin Range
Frequency
Selling price
$ 12,00 1 50
$ 195,00
$ ,00 -
Cost
$ 7,50 2
$ ,00
Discount price
$ 6,00 3 90
$ 315,00
$ ,00 16 4 40
$ 135,00
$ ,00
Probability 5 80
$ ,00
1/6 6 70
$ ,00 7 60
$ 255,00
$ ,00 18 8
$ ,00 9
$ ,00 10
$ ,00 11
$ ,00 12
$ ,00
Order Quantity 13
$ ,00 14
$ ,00 15
$ ,00 48
Random Number Range
$ ,00 17
$ ,00
1/3
$ ,00
1/2 19
2/3 20
Average Profit
$253,80
5/6 21
Standard Dev.
$ 68,74
Data Table Analysis
Order Quantity
$253,80 40
$180,00 50
$213,60 60
$240,60 70 80
$267,00 90
$269,40

9. STEP 2: Worksheets Design
4. Output Sheet:
Most important sheet for users.
Should clearly summarize results and calculations, so the user can understand the behavior of the system.
Summary tables and reports
Graphs, charts or histograms
Navigational output buttons
“End”, “Resolve”, and “View” buttons.

10. STEP 2: Worksheets Design
Outputs for Dave’s Candies Simulation Model
Order Quantity
Expected Profit 40
$180,00 50
$213,00 60
$236,40 70
$254,40 80
$271,80 90
$259,20

11. STEP 2: Worksheets Design
An output sheet example using pivot tables and pivot charts
Naviagational output sheet
Pivot tables are used to transform large amount of data from a table or database into an organized summary report

12. Step 3: User Interface The aim is to develop a user friendly DSS
Types of user interface in spreadsheet based DSS applications:
Navigational Buttons
Form Controls on the Worksheet
User Forms
Functional Buttons
During development of the DSS use these options to perform
Navigate the users through the application
Receive input
Allow users to input parameters of the model
Allow users to begin a calculation
Repeat a calculation or resolve a model

13. Navigational Buttons
The first navigational button we should create is the “Start” button, which is located on the “Welcome” sheet.
Assign this button to a macro that brings the users to the input interface
On all other sheets (input, calculation, and output sheets) there should at least be an “End” or “Exit” button.
The users should always have the option to quit the application and return to the Welcome sheet.
Be consistent in the phrases used for exit and end.
We may also include navigational buttons such as “Next,” “Continue,” or “Back” if we intend for the users to be able to step through the sheets or to revisit sheets.
Start

14. Receiving Input: Form Controls on the Worksheet
Form controls can make a worksheet into a dynamic user interface
Useful when there are many resolve options. In this case easy access to input data is needed.
A DSS for Inventory Management
Extra inputs are asked if backorders or reorder point model is selected.
This botten is not highlighted if standard eoq model is selected

15. Receiving Input: User Forms
Forms should be used when
the back and forth movement between the input and output worksheets is not very frequent.
there is large set of input required from the user.
There are many control options on forms:
control buttons are more clearly displayed; do not interfere with other cells on the worksheet,
can be displayed to the users at any time, since they are not attached to a worksheet. (useful for resolve options)
Possible to design dynamic user forms
Functional buttons on a worksheet
Functional buttons on a form

16. Receiving Input: User Forms
You can also design dynamic user forms. (

17. Receiving Input: User Forms
You can also place a “floating” form in a worksheet. Should be used when the user needs to modify input multiple times; the users can modify entries without any need to close the form. The form is hidden when the users move to another sheet.

18. Functional Buttons
In the case in which input, calculations, and/or output are combined, we may also include some functional buttons on the worksheet, such as “Solve.”
Quite advantageous, mostly used when large amounts of input are needed.
Initially Create table is higlighted.
When the users press it, they are prompted to give the dimensions.
The table with corresponding number of rows is created
Then solve button becomes visible

19. Step 4: Procedures
It is recommended to organize the code into several smaller procedures that may be called from other main procedures or associated with buttons on the worksheet.
Make an outline of what procedures you will need to conduct the flow and execute the calculations.
Receiving Input
Model and Calculations
Output Analysis and Display
Navigational
Make this outline before you begin the details of the implementation.
Draw up an outline of these procedures via comments in the code like procedure names, documentation, tasks performed, etc.

20. Step 4: Procedures Initial Procedures and Receiving Input
Main: Associated with the start button on the welcome sheet
Call ClearPrevious procedure
Show input form or take user to input sheet
Clear Previous:
Clear previous ranges of input or solution values
Initialize variables
Receive Input:
Store values from form controls or input cells to corresponding variables
Record these values to appropriate cells in calculation sheet

21. Step 4: Procedures Perform Model Calculations:
Perform calculations using function procedures
Run simulations using loops
Perform optimization using Solver commands
Perform Output Analysis and Generate Display:
Display solution values to an output “report table”
Update source data of the “chart” or “histogram”
Navigational Procedures:
“End”, “Next”, “Back”, or “View” button functionality
Change Visible property of worksheets

22. Step 4: Procedures - Variable Definitions
Variables:
All variables are declared
Variables used in more than one procedure are declared as “public” variables at the top of the module

23. Step 5: Resolve Options
A DSS should provide resolve options for the users!
Change inputs and resolve
Add new constraints, redefine objective function
In developing the re-solve options, we may ask the following questions:
Can the user easily modify the input to resolve the problem without having to re-enter all input from scratch?
Keep the last saved inputs, do not clear inputs unless the application is restarted
Can the user change other parts of the calculations or model when resolving?
Develop a dynamic application, so that different problem sizes are applicable.
If not, indicate in the welcome sheet.
What the user is really interested in learning from the DSS?
Store multiple solutions for senario comparison and sensitivity analysis
Remember that a DSS is designed to aid a decision maker in making a decision.

24. Resolve Options Examples
Returning to Simulation or Re-solve options
DSS suggests a resolve option for the simulation.
Suggestion is made by solving an optimization model

25. Resolve Options Examples (cont’d)
Changing Input or Portfolio options

26. Testing and Final Packaging
Testing is an important final step which ensures that the DSS performs as intended.
Test Navigation: Simply check all navigational options in each step of the application. Consider having an unbiased user test your program as well.
Test Calculation Correctness: Use a simple set of input values and check the calculation results. You may also use debugging techniques (see Appendix B) and error checking methods.
The final packaging should ensure that our DSS has a professional appearance.
All user interface should have clear instructions and be nicely and consistently formatted.

27. Summary
There are six basic steps to develop a DSS application: Application Overview, Worksheets, User Interface, Procedures, and DSS Components.
The outline of the worksheets in the DSS should include Welcome Sheet, Input sheet, Calculations sheet, and Output sheet.
The worksheet user interface includes Navigational Buttons, Functional Buttons, Controls on the Worksheet, and User Forms.
The outline of the procedures in the application should include a Main procedure, a Clear Previous procedure, a procedure to receive input, some procedures and functions to perform calculations, and a procedure to generate output.
In designing the re-solve options, the developers should check that the users are able to modify inputs, calculation options, constraints, and objectives. Aid the decision-makers in making the best decision.
The testing and final packaging step ensures that the DSS application works correctly and has a professional appearance for the end users.