Introduction of vp:valid (time:Interval)

[Certiman]

Several classes in VPA have an issue date, and are themselves valid from a given beginning date, for a specific duration or until a certain end date.

This can be expressed as:

# subClassOf vpa:DocumentedEvidence
era:doc-uuid_of_document a era:ECCertificate ; 
        dct:issued "issue_date"^^xsd:date ;
        vp:valid [ 
            a time:Interval ; # TemporalEntity
            time:hasBeginning  [
                a time:Instant ;
                time:inXSDDate "start_date_of_validity"^^xsd:date
            ] ;
            time:hasDurationDescription [
                a time:DurationDescription ;
                time:years 2 ;
            ] # If absent, unlimited duration
        ];
  ...

For DocumentedEvidence with a start and end date, time: also provides:

# subClassOf vpa:DocumentedEvidence
era:doc-uuid_of_document a era:ECCertificate ; 
        dct:issued "issue_date"^^xsd:date ;
        vp:valid [ 
            a time:Interval ; # TemporalEntity
            time:hasBeginning  [
                a time:Instant ;
                time:inXSDDate "start_date_of_validity"^^xsd:date
            ] ;
            time:hasEnd [
                a time:Instant ;
                time:inXSDDate "end_date_of_validity"^^xsd:date ;
            ] # If absent, unlimited duration
        ];
  ...

From time:, we hence use:

• time:Interval, time:Instant, time:DurationDescription
• time:hasBeginning, time:hasEnd, time:hasDurationDescription,
• time:years