Difference between revisions of "Pt:XMP"

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O XMP (Extensible Metadata Platform) facilita a incorporação de metadados em ficheiros, usando um subconjunto do RDF. Em especial, o XMP suporta a incorporação de matedados no formato PDF em muitos formatos de imagem, embora tenha sido desenhado para suportar praticamente qualquer tipo de ficheiro.

A Creative Commons recomenda o XMP como formato preferido para a incorporação de mateadados, dado o seu suporte de numerosos formatos de ficheiro e o estado fraccionado e antagónico dos padrões de incorporação de metadados. Outras entidades têm chegado à mesma conclusão; a Microsoft anunciou suporte para o XMP nas aplicações do Vista e Jon Udell comentou "Também existe um bom suporte no .NET Framework 3.0 para a leitura e escrita de metadados XMP." Note que mesmo quando contém metadados XMP incorporados a Creative Commons recomenda uma obra licenciada inclua um anúncio visível de direitos de autor; estão disponíveis recomendações específicas para diferentes formatos de anúncios visíveis.

The Creative Commons licensing process offers a XMP template which may be used to mark files within XMP-supporting Adobe applications (step-by-step how-to document). An XMP FileInfo panel is also available.

Specifying License Information

XMP defines a rights management schema (see XMP Specification, p. 42). Creative Commons sets the following properties (example values):

• xmpRights:Marked — False if Public Domain, True otherwise.
• xmpRights:WebStatement — http://example.com/pdf-metadata.html (Replace with URL containing metadata about the XMP-embedded file; this is referred to as the Web Statement.)
• xmpRights:UsageTerms — An optional field describing legal terms of use; Creative Commons recommends that when present this take the form This work is licensed to the public under the Creative Commons Attribution-ShareAlike license http://creativecommons.org/licenses/by­sa/2.0/ verify at http://example.com/pdf­metadata.html (Replace URL following 'verify at' with URL containing metadata about the XMP-­embedded file; this is typically the URL specified by xmpRights:WebStatement.)

This work is licensed to the public under the Creative Commons Attribution-ShareAlike license http://creativecommons.org/licenses/by-sa/2.0/ verify at http://example.com/pdf-metadata.html (Replace URL following 'verify at' with URL containing metadata about the XMP-embedded file; this is typically the same URL specified by xmpRights:WebStatement.)

We also define a Creative Commons schema http://creativecommons.org/ns# whose common prefix is cc. It currently has the following properties:

• license — The license URL; for example, http://creativecommons.org/licenses/by-sa/2.0/.
• morePermissions — A URL where additional permissions (commercial licensing, etc) are available.
• attributionURL — The URL to use when attributing this work.
• attributionName — The creator's preferred name to use when attributing this work.

Verification Links and XMP

A publisher can add boost confidence in embedded metadata by providing a verifying web statement. A verifying web statement is a URL which contains metadata with assertions matching those embedded in the file. The difference is that instead of making the assertions about a URL, the assertions are made in reference to the SHA-1 hash of the file.

For example, the example web statement http://example.com/pdf-metadata.html would include metadata encoded as RDFa.

  <p>The document example.pdf is licensed under a 
     <a about="urn:sha1:MSMBC5VEUDLTC26UT5W7GZBAKZHCY2MD" rel="license" 
        href="http://creativecommons.org/license/by/3.0/">
          Creative Commons Attribution 3.0</a> license.
     </a>
  </p>

When processing a file containing an embedded web statement, an application can retrieve the statement and parse it for additional metadata. If matching assertions are found which apply to the calculated SHA-1 hash of the file, the application can display an indicator noting increased confidence in the metadata. This approach has the added benefit of taking advantage of an existing mechanism (copyright take-down procedures) in order to break the confidence in the case of inappropriately licensed material.

Additional Information

• XMP Implementations
• All XMP-related articles
• Wikipedia article
• Adobe XMP FileInfo Panel

The XMP logo is either a registered trademark or trademark of the Adobe Systems Incorporated in the United States and/or other countries.