January 2012 Volume 15 Number 1 - Educational Technology ...

if x include with y, and y include with z then x include with z.
Rule expression
if include(x, y) and include(y, z) then include(x, z)
Constraint 4. inverse property
OWL expression
Semantic meaning
There is an inverse relation between application and standard.
Rule expression
if application (x, y) then standard(y, x)
XML-based RuleML Logic Program
The RuleML data model can represent Horn clause rules. An OWL class is treated as a unary predicate. An OWL
property is treated as a binary predicate. Assertions about instances in a class are treated as rule atoms (e.g., facts) in
which the class predicate appears. Assertions about property links between class instances are treated as rule atoms
in which the property predicate appears. RuleML allows a predicate symbol to be a URI; this capability is used
significantly herein, since the names of OWL classes are URIs.
Example 4 presents a RuleML rule for the non-monotonic rule that shows in the rule layer of Figure 1. This rule
requires the representation of complex implications, a capability that goes beyond the simple implications available
in OWL. This example indicates that RuleML not only provides a general implication in the form of Horn clauses,
but also that its XML representation makes it the ideal choice for use with OWL. The SoPro ontology is defined in
the previous section, and all its classes and properties are available to be used as elements in the rule. The RuleML
rules file consists of only the LOFinder rulebase.
Example 4.
RuleML expression
treeModeXML DOM
XMLParserXMLJAXP
usingJAXPDOM
Rule expression
if XMLParser(XML, JAXP) and using(JAXP, DOM)
then treeMode(XML, DOM)
Inference meaning
If an XML course adopts a JAXP parser that is developed by DOM then the XML course adopts DOM method to
extract data.
LOM Metadata
The software domain in the example represents all learning objects as HTML documents. The following discussion
illustrates how LOM can be used to annotate relationships of learning objects using the concrete examples in the
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