RE: linked open data and PDF

I wrote:
> > Image formats like JPEG and PNG (for which there
> > is support for XMP) don't have a standard, uniform
> > way of attaching other files, though, so allowing
> > data (or a pointer to external data) in the XMP
> > would broaden the applicability.

And Michael Brunnbauer replied:
 > I am right that such a pointer to external data would have to be a literal?
> The way I read the XMP standard is that only literals, blank nodes,   rdf:Bag and rdf:Seq are allowed as object of a triple.

No, URI is allowed as a simple type in XMP, so I think all you need is a Linked Data schema.
But XMP uses rdf:Bag with named components to hold structures, and the ResourceRef structure can be used to link documents by the InstanceID GUID as well as file location (ManageFrom).


http://www.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/DynamicMediaXMPPartnerGuide.pdf has some examples.

> This would rule out standard options like:
> 
>   <this_document> rdfs:seealso <rdf_document_about_pdf_document>
>   <this_document> owl:sameAs <pdf_document_uri>
> 
> Which would enable agents to find and regognize RDF data about the
> document.

      <rdf:Description rdf:about=""
            xmlns:pdf="http://ns.adobe.com/pdf/1.3/"
            xmlns:xmp="http://ns.adobe.com/xap/1.0/"
            xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
            xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
            xmlns:owl_1_="http://www.w3.org/2002/07/owl#"
            xmlns:dc="http://purl.org/dc/elements/1.1/">
         <pdf:Producer>Microsoft® Excel® 2013</pdf:Producer>
         <xmp:CreatorTool>Microsoft® Excel® 2013</xmp:CreatorTool>
         <xmp:CreateDate>2015-01-21T09:26:54-08:00</xmp:CreateDate>
         <xmp:ModifyDate>2015-01-23T14:55:44-08:00</xmp:ModifyDate>
         <xmp:MetadataDate>2015-01-23T14:55:44-08:00</xmp:MetadataDate>
         <xmpMM:DocumentID>uuid:895A48D2-1F07-442F-A374-FB045D560C9B</xmpMM:DocumentID>
         <xmpMM:InstanceID>uuid:a3962424-bf4c-4e33-8475-013b5ad35ace</xmpMM:InstanceID>
         <rdfs:seealso>http://example.org/rdf-document</rdfs:seealso>
         <owl_1_:sameAs>http://5stardata.info/gtd-5.html</owl_1_:sameAs>
         <dc:format>application/pdf</dc:format>
         <dc:title>