How to represent sales invoice and posting period in RDF/OWL?

[heidan]

Dear,

I have a question of representing the relationship of sales invoice's
posting date and post period into RDF.

Let's say every sales invoice has a posting date which records when
this invoice is created; posting period has a 'from posting date' and
'to posting date'; Every sales invoice must be posted into one posint
period, that implies following conditions.

sales_invoice.posting_date in [posting_period.from_posting_date,
posting_period.to_posting_date)

If I have RDF definition of both sales_invoice and posting_period as
below, how do I define the relationship above?

<?xml version="1.0"?>
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns="http://www.owl-ontologies.com/unnamed.owl#"
xml:base="http://www.owl-ontologies.com/unnamed.owl">
<owl:Ontology rdf:about=""/>
<owl:Class rdf:ID="PostingPeriod"/>
<owl:Class rdf:ID="Document"/>
<owl:DatatypeProperty rdf:ID="PostingFromDate">
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#time"/>
<rdfs:domain rdf:resource="#PostingPeriod"/>
</owl:DatatypeProperty>
<owl:DatatypeProperty rdf:ID="PostingToDate">
<rdfs:domain rdf:resource="#PostingPeriod"/>
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#time"/>
</owl:DatatypeProperty>
<owl:DatatypeProperty rdf:ID="PostingDate">
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#time"/>
<rdfs:domain rdf:resource="#Document"/>
</owl:DatatypeProperty>
</rdf:RDF>
Thanks,
heidan