models kieran mathieson. outline what are models? what are models for? process models data...
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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
Example
Start
Take order
Check orderwith customer
Get paymentinformation
Get shippinginformation
Check shippinginformation
with customer
Check paymentinformation with
customer
Creditauthorized?
Refer customerto manager
Ordercomplete
YesNo
Example
Department Employee
TeamSkills
ProjectProductCustomer
manages
employs
manages
in
has
deliversbuys
has
http://db.grussell.org/section021.html#_Toc67114582
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
Process Models
Most process models represent activities
Wake
Hungover?
Go to class
Study
Lunch
Hungover?
Dinner
Bed
Yes
Yes
No
No
Process Models
Some models represent other aspects of processes than activities
http://www.cs.utoronto.ca/~eric/ieeeexp/ieeeexp2.html
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?
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
Entity Relationship Model
Department Employee
TeamSkills
ProjectProductCustomer
manages
employs
manages
in
has
deliversbuys
has
http://db.grussell.org/section021.html#_Toc67114582
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
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
Optimization Model (cont.)
A = W ( 1000 – 2 W ) A = 2W2 – 1000 W dA / dW = 4W – 1000 dA / dW = 0 when W = 250
Jetty
BuildingsW
1,000 – 2W
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