<?xml version="1.0" encoding="UTF-8"?><Assert xmlns="http://www.ruleml.org/0.88/xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.ruleml.org/0.88/xsd http://www.ruleml.org/0.88/xsd/datalog.xsd">	<!-- start XML comment ...Note: This is a compact (i.e. minimally-roled) version of this example.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 -->	<content>		<And innerclose="universal">			<formula>				<Implies>					<!-- explicit 'And' -->					<body>						<And>							<formula>								<Atom>									<opr>										<Rel>buy</Rel>									</opr>									<arg index="1">										<Var>person</Var>									</arg>									<arg index="2">										<Var>merchant</Var>									</arg>									<arg index="3">										<Var>object</Var>									</arg>								</Atom>							</formula>							<formula>								<Atom>									<opr>										<Rel>keep</Rel>									</opr>									<arg index="1">										<Var>person</Var>									</arg>									<arg index="2">										<Var>object</Var>									</arg>								</Atom>							</formula>						</And>					</body>					<head>						<Atom>							<opr>								<Rel>own</Rel>							</opr>							<arg index="1">								<Var>person</Var>							</arg>							<arg index="2">								<Var>object</Var>							</arg>						</Atom>					</head>				</Implies>			</formula>			<!-- The second rule implies that a person buys an object from a merchantif the merchant sells the object to the person. -->			<formula>				<Implies>					<body>						<Atom>							<opr>								<Rel>sell</Rel>							</opr>							<arg index="1">								<Var>merchant</Var>							</arg>							<arg index="2">								<Var>person</Var>							</arg>							<arg index="3">								<Var>object</Var>							</arg>						</Atom>					</body>					<head>						<Atom>							<opr>								<Rel>buy</Rel>							</opr>							<arg index="1">								<Var>person</Var>							</arg>							<arg index="2">								<Var>merchant</Var>							</arg>							<arg index="3">								<Var>object</Var>							</arg>						</Atom>					</head>				</Implies>			</formula>			<!-- The third rule is a fact that asserts thatJohn sells XMLBible to Mary. -->			<formula>				<Atom>					<opr>						<Rel>sell</Rel>					</opr>					<arg index="1">						<Ind>John</Ind>					</arg>					<arg index="2">						<Ind>Mary</Ind>					</arg>					<arg index="3">						<Ind>XMLBible</Ind>					</arg>				</Atom>			</formula>			<!-- 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 -->			<formula>				<Atom>					<opr>						<Rel>keep</Rel>					</opr>					<arg index="1">						<Ind>Mary</Ind>					</arg>					<arg index="2">						<Ind>XMLBible</Ind>					</arg>				</Atom>			</formula>		</And>	</content></Assert>