Difference Analysis Generated by HtmlDiff on 5/12/2005 2:39 PM  

 

<?xml version="1.0" encoding="UTF-8"?>  
<Assert xmlns="http://www.ruleml.org/0.88/89/xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.ruleml.org/0.88/89/xsd http://www.ruleml.org/0.88/89/xsd/datalog.xsd">   
<!-- start XML comment ...

This example rulebase contains four rules.
The first and second rules are implications; the third and fourth ones are facts.

In English:

The first rule implies that a person owns an object
if that person buys the object from a merchant and the person keeps the object.

As an OrdLab Tree:

Implies~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          *                         *
     head *                    body *
          *                         *
        Atom~~~~~~~~~~~~~~~~~~     And~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                 *     |     |           |                                   |
             opr *     |     |           |                                   |
                 *     |     |           |                                   |        
                Rel   Var   Var        Atom~~~~~~~~~~~~~~~~~~~~~~~~~~~     Atom~~~~~~~~~~~~~~~~~~
                 .     .     .                  *     |      |       |              *     |     |
                 .     .     .              opr *     |      |       |          opr *     |     |
                 .     .     .                  *     |      |       |              *     |     |
                own  person object             Rel   Var    Var     Var            Rel   Var   Var
                                                .     .      .       .              .     .     . 
                                                .     .      .       .              .     .     .
                                                .     .      .       .              .     .     .
                                               buy  person merchant object        keep  person object

... end XML comment -->  
<And innerclose="mapClosure="universal">        
<Implies>   
<head>     
<Atom>       
<opr>
<Rel>own</Rel>
</opr>       
<Var>person</Var>       
<Var>object</Var>     
</Atom>   
</head>   
<body>     
<!-- explicit 'And' -->     
<And>       
<Atom>         
<opr>
<Rel>buy</Rel>
</opr>         
<Var>person</Var>         
<Var>merchant</Var>         
<Var>object</Var>       
</Atom>       
<Atom>         
<opr>
<Rel>keep</Rel>
</opr>         
<Var>person</Var>         
<Var>object</Var>       
</Atom>     
</And>   
</body> 
</Implies>  
<!-- The second rule implies that a person buys an object from a merchant
if the merchant sells the object to the person. -->  
<Implies>   
<head>     
<Atom>       
<opr>
<Rel>buy</Rel>
</opr>       
<Var>person</Var>       
<Var>merchant</Var>       
<Var>object</Var>     
</Atom>   
</head>   
<body>     
<Atom>       
<opr>
<Rel>sell</Rel>
</opr>       
<Var>merchant</Var>       
<Var>person</Var>       
<Var>object</Var>     
</Atom>   
</body> 
</Implies>     
<!-- The third rule is a fact that asserts that
John sells XMLBible to Mary. -->       
<Atom>       
<opr>
<Rel>sell</Rel>
</opr>       
<Ind>John</Ind>       
<Ind>Mary</Ind>       
<Ind>XMLBible</Ind>     
</Atom>    
<!-- The fourth rule is a fact that asserts that
Mary keeps XMLBible.
 
Observe that this fact is binary - i.e., there are two arguments
for the relation. RDF viewed as a logical knowledge representation
is, likewise, binary, although its arguments have type restrictions,
e.g., the first must be a resource (basically, a URI). Some of the
DTD's on the RuleML website handle URL's/URI's (UR's); see especially
urc-datalog.dtd for inferencing with RDF-like facts -->       
<Atom>       
<opr>
<Rel>keep</Rel>
</opr>       
<Ind>Mary</Ind>       
<Ind>XMLBible</Ind>     
</Atom>  
</And>    
</Assert>