Simplifying Decision Tables - YouTube

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>> David Durant: Welcome to this presentation on simplifying decision tables.

Only limited entry decision tables can be simplified

and usually in conjunction with a completeness check.

You will see in this video how we will take a complex set of rules

and express them as a decision table

and then simplify the table using a logical process.

Let us look at an example that shows how a set of complex rules

can be expressed as a decision table

and then simplified using a rigorous, logical process.

The end result is much easier to read and maintain.

This limited-entry decision table

is to decide whether to accept or reject a customer's order.

There are three conditions.

Hs the customer's credit limit been exceeded?

Are they a prompt payer?

Do they have special clearance?

The associated action,

depending on the combination of the conditions,

is to either accept the order or to reject it.

This is our simplifying rule...

Any two rules which have identical entries except for one condition rule

which contains a Y and N

may be consolidated into one rule

which contains a dash in place of the Y and N.

Obviously, the rules must have the same action.

So in the example, we can simplify rules 7 and 8.

They have the same action and differ only by the Y and N in the third condition

So the resulting consolidated rule will become N N - X -

Rules 5 and 6 can be simplified to the rule N Y - X -

However, rules 1 and 2 can't be simplified because they have a different action.

But rules 1 and 3 can be. To give Y - Y X -

And finally, rules 2 and 4

can be consolidated to give the rule Y - N - X

So the resulting table

will have four rules.

This table can be simplified further.

If we look at the rules 3 and 4,

we see they are identical except for the second condition

Is the customer a prompt payer?

By simplifying these two rules,

the resulting table

will just have three.

A third rule N - - X -

This table cannot the simplified any further

using the simplifying rules.

We can see that condition test 2

Is the customer a prompt payer?

is no longer relevant and can be removed.

One final thing we can do

is to keep rule 2

and replace rules 1 and 3 with an Else rule.

In simplifying the decision table,

we have logically reduced the 8 rule table

to 1 rule and the Else rule.

The resulting decision table

is to only reject the order

where the customer has exceeded the credit limit

and they don't have special clearance.

Otherwise we will accept it.

I hope you found this video useful.

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