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jDREW

 
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Instructions on the applet demo

This Applet demo illustrates a simple bottom-up inference engine built from the jDREW package. The engine will take a set of “rules” and “facts” as input and inference bottom-up through them. The output of the engine is an exhaustive set of “facts” that can be derived from the input set. The demo provides three preset example input sets to illustrate how the engine works. Also, the users can use their own “rule” and “fact” sets in the demo.

The demo GUI has a “Format” radio button group, a “Trace” check box, an “example” selection box and a “Run” button:

· “Example” selection box: a combo box to select an example input set that you want to run. (See picture 1) By selecting the “user input”, you can type in your own “rules” and “facts” in “Prolog” or “RuleML” format.

· “Format” radio button group: indicates the format (“Prolog” or “RuleML”) of the input set. Select it correctly when you are using “user input”.

· “Trace” check box: click “Run” when unchecked, the demo only gives the finial exhaustive set of “ facts” that can be derived from the input set. (See picture 2)

click “Run” when checked, the demo will give the processing details of the bottom-up inference. (See picture 3)

· “Run” button: click to start the bottom-up inference.

· “Console” tab window: holds the output from the demo.

· “Rule Set” tab window: holds the current input set for the demo.

Picture 1	Picture 3
Picture 2

The explanation of the process details:

Data structure: New facts: priority queue.

Old facts: Discrimination tree.

Rules: Discrimination tree.

Initial stage

New facts <- all the facts of the input set.

Old facts <- empty.

Rules <- all the rules of the input set.

Process:

Main loop

loop until New facts is empty

select and remove a new fact n from New facts

if n is not forward subsumed by the facts in old facts

for each rule in Rules whose first goal matches n

resolve

process new result

add n to old facts

“Selected newFact n” message is outputted at this step as a trace info.

	“new fact n subsumed by old fact …” message is outputted at this step if n is subsumed by the facts in old facts.
	“new resolvent …” message is outputted at this step as a trace info.

Process new result (c)

If c is rule

For each old fact in old facts that matching the first goal of c

resolve

process new result

add c to Rules

else

add c to New facts

	“new resolvent …” message is outputted at this step as a trace info.