Difference Analysis Generated by HtmlDiff on 2/2/2005 10:28 AM  

 
<?xml version="1.0" encoding="UTF-8"?>

<Rulebase Assert xmlns="http://www.ruleml.org/0.87/88/xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.ruleml.org/0.87/88/xsd http://www.ruleml.org/0.8788/xsd/datalog.xsd">

<!-- start XML comment ...
    <And innerclose="universal">
        <!-- 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:

 imp~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          *                         *
     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 -->


<Imp>
        <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
        <!-- The second rule implies that a person buys an object from a merchant
if the merchant sells the object to the person. -->

<Imp>
        <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
        <!-- The third rule is a fact that asserts that
John sells XMLBible to Mary. -->
 
<Fact>
  <head>
    <Atom>
      <opr><Rel>sell</Rel></opr>
      <Ind>John</Ind>
      <Ind>Mary</Ind>
      <Ind>XMLBible</Ind>
    </Atom>
  </head>
</Fact>
 
        <!-- 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 -->
 
<Fact>
  <head>
    <Atom>
      <opr><Rel>keep</Rel></opr>
      <Ind>Mary</Ind>
      <Ind>XMLBible</Ind>
    </Atom>
  </head>
    </And>
</FacAssert>
  
</Rulebase>