HowTo/XMP

XMP (Extensible Metadata Platform) provides a standard to work with metadata.

This page describes how to declare such metadata in an XSL-FO file.

This works only with FOP trunk.

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Declaring properties in an XSL-FO file

All metadata properties can be declared in the fo:declarations element.

XMP specification recommends to use x:xmpmeta, rdf:RDF, and rdf:Description elements as shown in example below.

Only one of the 2 first is required to make PDF to recognize metadata properties.

Example

[..]
</fo:layout-master-set>
<fo:declarations>
        <x:xmpmeta xmlns:x="adobe:ns:meta/">
                <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
                        <rdf:Description rdf:about=""
                                xmlns:dc="http://purl.org/dc/elements/1.1/">
                                <!-- Dublin Core properties go here -->
                                <dc:title>Document title</dc:title>
                                <dc:creator>Document author</dc:creator>
                                <dc:subject>Document subject</dc:subject>
                        </rdf:Description>
                        <rdf:Description rdf:about=""
                                xmlns:xmp="http://ns.adobe.com/xap/1.0/">
                                <!-- XMP properties go here -->
                                <xmp:CreatorTool>Tool used to make the PDF</xmp:CreatorTool>
                        </rdf:Description>
                </rdf:RDF>
        </x:xmpmeta>
</fo:declarations>
<fo:page-sequence ...
[..]

fo:declarations must be declared after fo:layout-master-set

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Implementation in Apache FOP

Currently, XMP support is only available for PDF output.

Until recently, you could set some metadata information through FOP's FOUserAgent by using its set*() methods (like setTitle(String) or setAuthor(String). These values are directly used to set value in the PDF Info object. Since PDF 1.4, adding metadata as an XMP document to a PDF is possible. That means that there are now two mechanisms in PDF that hold metadata.

Apache FOP now synchronizes the Info and the Metadata object in PDF, i.e. when you set the title and the authort through the FOUserAgent, the two values will end up in the (old) Info object and in the new Metadata object as XMP content. If instead of FOUserAgent, you embed XMP metadata in the XSL-FO document (as shown above), the XMP metadata will be used as-is in the PDF Metadata object and some values from the XMP metadata will be copied to the Info object to maintain backwards-compatibility for PDF readers that don't support XMP metadata.

The mapping between the Info and the Metadata object used by Apache FOP comes from the PDF/A-1 specification. For convenience, here's the mapping table:

Note: "Internal" in the Category column means that the user should not set this value. It is set by the application.

Properties sets

Metadata is made of properties sets.

Properties sets are:

Dublin Core set

XMP basic set

(1) These properties are "Internal" properties and must not be set my the user.

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Links

• XMP specification

• http://dublincore.org/

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