paulmillar commented on issue #1663: URL: https://github.com/apache/jena/issues/1663#issuecomment-1338210853
Hi all, Just to tidy up some loose ends, I've checked the XMP and PDF specifications. [XMP part 1](https://raw.githubusercontent.com/adobe/XMP-Toolkit-SDK/main/docs/XMPSpecificationPart1.pdf), section 7.4 ("rdf:RDF and rdf:Description elements") says: > If the XMP data model has an AboutURI (6.1, “XMP packets”), that same URI shall be the value of an rdf:about attribute in each top-level rdf:Description element. Otherwise, the rdf:about attributes for all top- level rdf:Description elements shall be present with an empty value. The rdf:about attribute shall not be used in more deeply nested rdf:Description elements. XMP part 1 provides very little information about this AboutURI concept beyond identifying it as the `rdf:about` attribute of all top-level `rdf:Description` elements. Anything more is deemed out-of-scope for the XMP specification. [XMP part 3](https://raw.githubusercontent.com/adobe/XMP-Toolkit-SDK/main/docs/XMPSpecificationPart3.pdf) defines how XMP is embedded in various files, including PDF. For PDF, part 3 gives an overview of how this is done, but also identifies the PDF specification as the authoritative definition on how XMP is embedded. Part 3 makes no mention of AboutURI. I checked [PDF v1.6](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.6.pdf) and this shows how embedded XMP is placed within the definition of the item to which it refers. These placement rules means the target of the XMP is dictated by the XMP packet's location within of the file. In addition, the PDF specification makes no mention of AboutURI (which, I think, makes sense). As there is no AboutURI, the RDF/XML (for an RDF graph describing an element within a PDF file) *MUST* contain only top-level `rdf:Description` elements that have a `rdf:about` attribute with an empty value. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
