<?xml version="1.0" encoding="UTF-8"?>
<?xml-model href="http://www.ruleml.org/1.0/relaxng/datalog_relaxed.rnc"?>
<!--<?xml-model href="http://www.ruleml.org/1.0/xsd/datalog.xsd" type="application/xml" schematypens="http://www.w3.org/2001/XMLSchema"?>-->
<RuleML xmlns="http://ruleml.org/spec"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://ruleml.org/spec http://www.ruleml.org/1.0/xsd/datalog.xsd">

  <Assert mapClosure="universal">

    <!-- start XML comment ...

    这个例子的规则库中包含了4个规则.
    第一和第二个规则是推断; 第三和第四个规则是事实.

    In English:

　　 The first rule implies that a person owns an object
    第一个规则推断：一个人拥有一个东西
    if that person buys the object from a merchant and the person keeps the object.
　　 如果这个人从商人手中购买了这个东西，并且最终这个人拥有了这个东西

    OrdLab Tree 如下:

    Implies~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
              *                                                                            *                       
           if *                                                                       then * 
              *                                                                            *  
             And~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                 Atom~~~~~~~~~~~~~~~~~~
                   |                                   |                                          *     |     |  
                   |                                   |                                      op  *     |     |  
                   |                                   |                                          *     |     |    
                 Atom~~~~~~~~~~~~~~~~~~~~~~~~~~~     Atom~~~~~~~~~~~~~~~~~~                      Rel   Var   Var
                          *     |      |       |              *     |     |                       .     .     .    
                      op  *     |      |       |          op  *     |     |                       .     .     .    
                          *     |      |       |              *     |     |                       .     .     .
                         Rel   Var    Var     Var            Rel   Var   Var                     own  person object
                          .     .      .       .              .     .     . 
                          .     .      .       .              .     .     .
                          .     .      .       .              .     .     .
                         buy  person merchant object        keep  person object

    ... end XML comment -->

    <Implies>
      <if>
        <!-- 申明 ‘And‘ 联结-->
        <And>
          <Atom>
            <op><Rel>buy</Rel></op>
            <Var>person</Var>
            <Var>merchant</Var>
            <Var>object</Var>
          </Atom>
          <Atom>
            <op><Rel>keep</Rel></op>
            <Var>person</Var>
            <Var>object</Var>
          </Atom>
        </And>
      </if>
      <then>
        <Atom>
          <op><Rel>own</Rel></op>
          <Var>person</Var>
          <Var>object</Var>
        </Atom>
      </then>
    </Implies>

  <!-- The second rule implies that a person buys an object from a merchant
　　　　第二个规则的推断：一个人从商人手中购买一个东西
  if the merchant sells the object to the person. 
　　　　如果商人将这个东西卖给这个人
  -->

    <Implies>
      <if>
        <Atom>
          <op><Rel>sell</Rel></op>
          <Var>merchant</Var>
          <Var>person</Var>
          <Var>object</Var>
        </Atom>
      </if>
      <then>
        <Atom>
          <op><Rel>buy</Rel></op>
          <Var>person</Var>
          <Var>merchant</Var>
          <Var>object</Var>
        </Atom>
      </then>
    </Implies>
 
  <!-- The third rule is a fact that asserts that
　　第三个规则是一个事实：John卖了XMLBible给Mary
  John sells XMLBible to Mary. -->
 

    <Atom>
      <op><Rel>sell</Rel></op>
      <Ind>John</Ind>
      <Ind>Mary</Ind>
      <Ind>XMLBible</Ind>
    </Atom>

 
  <!-- The fourth rule is a fact that asserts that
　　　　第四个规则是一个事实：Mary拥有XMLBible
  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). 
　　我们观察到这个事实是二元的：关系有两个参数。
　　RDF被看作是一种合理的知识表现形式，同样的、二元的，虽然它的参数类型有限制，比如第一个必须是资源

　　-->
 
    <Atom>
      <op><Rel>keep</Rel></op>
      <Ind>Mary</Ind>
      <Ind>XMLBible</Ind>
    </Atom>
  
  </Assert>

</RuleML>