1. Models Kieran Mathieson

2. Outline  What Are Models?  What Are Models For?  Process Models  Data Models  Decision Models

3. What Are Models?  Representation of something  Not as complex as the real thing  Omits details  Different types of models for different tasks Accurate models are a critical IT resource

4. Example http://www.flexsim.com

5. Example http://www.flexsim.com

6. Example

7. Start Take order Check order with customer Get payment information Get shipping information Check shipping information with customer Check payment information with customer Credit authorized? Refer customer to manager Order complete Yes No

8. Example

9. http://db.grussell.org/section021.html#_Toc67114582

10. What Are Models For?  Understand  Figure out how something works  Communicate  Show others how it works  Improve  Can't improve something you don't understand  Predict  What will happen if we …  Automate  Replace parts with IT

11. Outline  What Are Models?  What Are Models For?  Process Models  Data Models  Decision Models

12. Process Models  Most process models represent activities Wake Hung over? Go to class Study Lunch Hung over? Dinner Bed Yes No

13. Process Models  Some models represent other aspects of processes than activities http://www.cs.utoronto.ca/~eric/ieeeexp/ieeeexp2.html

14. Process Model Issues  How much detail?  How do you organize complexity?  How concrete?  If Jim does a task, do you put a symbol for Jim on the diagram, or just represent the task?  How do you maintain process models?

15. Outline  What Are Models?  What Are Models For?  Process Models  Data Models  Decision Models

16. Data Models  Represents the data needed to support processes  Drives database implementation  Errors in process models lead to errors in data models lead to errors in database implementation lead to errors in applications lead to long weekends at work

17. Entity Relationship Model http://db.grussell.org/section021.html#_Toc67114582

18. UML Class Model

19. Outline  What Are Models?  What Are Models For?  Process Models  Data Models  Decision Models

20. Decision Models  Mathematical representation of a situation  Simulations models  Build software that more-or-less directly mimics the situation  Software elements act like real elements  Optimization models  Use a well-known mathematical technique to find the best answer to a problem

21. Simulation Model SimCity 4

22. Optimization Model  You have a supply depot on a river  You want to install a security fence  You have 1,000 feet of left-over fencing  What’s the most space you can enclose? Jetty Buildings

23. Optimization Model (cont.)  A = W ( 1000 – 2 W )  A = 2W2 – 1000 W  dA / dW = 4W – 1000  dA / dW = 0 when W = 250 Jetty Buildings W 1,000 – 2W

24. Outline  What Are Models?  What Are Models For?  Process Models  Data Models  Decision Models There are lots of models in IS. Accurate models are a critical resource.