Difference between revisions of "Marking Works Technical"

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Visible notice as above. [[XMP]] metadata, which has advantages and disadvantages:
Visible notice as above. [[XMP]] metadata, which has advantages and disadvantages:
* Constrained RDF -- very expressive, compatible.
* Constrained RDF -- very expressive, compatible.
  * Web reference: value of <code>xapRights:WebStatement</code>
  * License: value of <code>cc:license</code>
* Not visible in document, nor linkable to visible fields.
* Not visible in document, nor linkable to visible fields.
* Very little exposure via <code>File|Document Properties</code> style interfaces -- only Photoshop CS file browser?
* Very little exposure via <code>File|Document Properties</code> style interfaces -- only Photoshop CS file browser?
* Very little support for embedding -- only Photoshop CS file browser and macro for Latex users?
* Very little support for embedding -- only Photoshop CS file browser, macro for Latex users and Java library/application?
== Audio ==
== Audio ==

Revision as of 01:57, 22 August 2006

I'm posting this here to get it off my laptop and motivate me to finish it. Please do not edit yet. Thanks. Mike Linksvayer 16:33, 15 May 2006 (UTC)

This article describes best practices for marking works licensed with a Creative Commons license or dedicated to the public domain with both human readable and machine readable notices, on the web and otherwise.

Although the importance of human-visible attribution and notice is stressed, this primary focus of this article is machine-readable metadata. Best practice for presentation of human-visible attribution and notice in various formats (apart from colocation with machine-readable equivalents) is currently beyond the scope of this article and will be presented elsewhere.


  • Copyright notice should be published on the web. Offline or peer-distributed works should refer to notice published on the web. A web notice allows content to be found via web search, content owners to be found by viewers of untethered works, may be trusted to the extent a web page may be trusted, and allows for further annotation by the owner and others.
  • Copyright notice should be visible and unambiguous to humans and computers, especially the former. Human and computer visible notices should be one and the same.
  • Copyright notice best practices should be general rather than applicable only to works offered under one of the Creative Commons licenses.


A web page is the preferred venue for published copyright notices. Notices published elsewhere should refer to an equivalent notice published on the web.

       This text is licensed to the public under the <a rel="license"
        Commons Attribution 2.5 License</a>.

That HTML snippet says that the current document is licensed under CC BY 2.5. The current document is the default subject, rel="license" sets the predicate or verb, the URL in the href value sets the object.

For detailed background on the web metadata model and syntax being used, see RDFa.

This use follows the aforementioned principles:

  • On the web (obviously, so long as the HTML page in question is published to a website).
  • The metadata is visible -- it is colocated with an actionable link and may further be styled with CSS for human consumption.
  • It is general -- the model used can accomodate any sort of statement about anything that has a URI and the license predicate can take any license that has a URI as its object, not only a Creative Commons license.

Now we will see how to use the model to further annotate works with licensing-relevant metadata.


A licensor can specify (see 4(b) of http://creativecommons.org/licenses/by/2.5/legalcode):

  1. name of author or designated entity
  2. title of work
  3. url associated with work referencing copyright
  4. identification of derivative use

Ideally all of these would be available as machine-readable metadata. I think the triples we want (assuming the work in question is the current document) are:

       1. <> cc:attributionName "James Roberts" .
       2. <> dc:title "Compact Representation of Blank Pages" .
       3. <> cc:attributionURL <http://example.org/crobp.html> .
       4. <> cc:derivativeDescription "aranslation of 'Paginas Blancos Si!'" .

Why the made up properties?

  1. dcterms:rightsHolder and dc:creator don't say which should be attributed -- or if someone else should be.
  2. not made up, dc:title works just fine.
  3. often this will be the current URL, but need some way to specify that it should be cited.
  4. dc:source refers to the source work, not how source work was reused.

Fortunately RDFa allows us to annotate human readable notices and include both the custom properties needed for attribution as well as additional useful properties, e.g.

       <a rel="cc:attributionURL" href="http://example.org/crobp.html"
       property="dc:title">Compact Representation of Blank Pages</a> by
       <a rel="dc:creator" href="http://example.org/jr.html"
       property="cc:attributionName">James Roberts</a>, a <a
       rel="dc:source" href="http://example.org/bps.html"
       property="cc:derivativeDescription">translation of 'Paginas
       Blancos Si!'</a>, is licensed to the public under the <a
       Commons Attribution 2.5 License</a>.

This produces the four triples above plus these:

       5. <> dc:creator <http://example.org/jr.html>
       6. <> dc:source <http://example.org/bps.html>
       7. <> license <http://creativecommons.org/licenses/by/2.5/>

Included Objects

Objects included in web pages (images) should be annotated as above within their "host" web pages. Ideally all included objects should also embed object format native notice and metadata as described below, but this is only crucial for objects where the publisher indends for or is concerned about distribution outside the context of the "host" web page.

Metadata about include objects that have their own URIs should be qualified with about, as rel="license" without an about attribute makes a statement about the current document (which is the "host" web page). Example:

       Photo licensed under <a about="http://example.com/some-image.png"
        rel="license" href="http://creativecommons.org/licenses/by/2.5/">cc by 2.5</a>.

See the RDFa Primer on beyond the current document for additional examples.

More Rights

A page may provide any sort of metadata for itself and its included components. The following example has some obviously useful statements:

       <span rel="dc:type" href="http://purl.org/dc/dcmitype/Sound"/>Audio</span> <a rel="license"
        href="http://creativecommons.org/licenses/by-nc/2.5/">(cc)</a> <span property="dc:date">2006</span>.
        See <a rel="cc:morePermissions" href="http://johnsmith.com/store">my store</a> to obtain permissions not
        granted by the CC license, signed CDs, and concert tickets.

In addition to the familiar license statement and dc:type from Dublin Core we have cc:morePermissions. The intention of cc:moreRights is to point to a URL at which one can discover permissions outside the scope of those granted to the public by the licensor via a CC license.

A prominent use case is Magnatune's commercial licensing system. Example:


In the example snippets above we have used the cc: and dc: namespaces without definition. To define a namespace for subsequent use include an xmlns attribute on the element in which the namespace is used on any parent element. Example:

       <span xmlns:dc="http://purl.org/dc/elements/1.1/" property="dc:title">My Book</span>

Interoperability with other web-based metadata formats


RDF/XML is another RDF serialization that can be used to make any statement that can be made with RDFa. RDF/XML may be <link>ed in the <head> of a web page or (deprecated CC recommendation) included in HTML comments. RDF/XML is perfectly interoperable with RDFa, but the latter is preferred as it is colocated with human-visible content.


RelLicense is both an elemental microformat (specifically rel license) and an RDFa statement. Compound Microformats should be interoperable via hGRDDL.


RSS1.0, RSS2.0, and Atom 1.0 syndication formats each may include license annotations. These should also be reflected on web pages referenced by feed items.


Objects not native to the web should adhere to the following principles regarding license notice and metadata.

  • To the extent possible copyright notice should be visible to users of the licensed object.
  • The licensed object should contain a web reference to a web page that provides an equivalent licensing notice for the object in question. This makes a non-web object's licesning status as certain as that of a web page's status -- if the web reference does not agree with the non-web object's license notice, ignore the latter.
  • To the extent possible license notice provided by non-web objects should use mechanisms and conventions in common use for the format of the non-web object in question.

We will now apply these principles to a variety of content formats.

Office Documents

"Office Documents" meaning word processor, presentation and spreadsheet files and document output formats such as PDF.

All of these formats are intended for human consumption and all modern versions support web links, so visibility is easy -- the license and web reference should be noted in thee document text wherever common use dictates a copyright notice would appear. Looks like we just took care of the other principles as well.

Many document formats support some form of embedded metadata that can be accessed, e.g., by selecting File|Document Properties from a menu. Where such metadata includes licensing or copyright-relevant fields, these should be populated with first priority to the web reference and second priority to the URL of the license the document in question is under.

Ideally these metadata fields should be used to directly populate the human-visible parts of the document, e.g., via a document field, as is typically used to automatically place page numbers and document titles throughout such documents. This gives us the best of both worlds -- any software that indexes embedded metadata can easily find license information, and that information is perfectly reflected in notices humans see.

What follows is a very incomplete accounting of how these guidelines may be used in various popular office document formats.

Microsoft Office

Visible notice as above. Metadata TBD.


Visible notice as above. Metadata TBD.


Visible notice as above. XMP metadata, which has advantages and disadvantages:

  • Constrained RDF -- very expressive, compatible.
 * Web reference: value of xapRights:WebStatement
 * License: value of cc:license
  • Not visible in document, nor linkable to visible fields.
  • Very little exposure via File|Document Properties style interfaces -- only Photoshop CS file browser?
  • Very little support for embedding -- only Photoshop CS file browser, macro for Latex users and Java library/application?



Still Images

Although possible, visible attribution and copyright notice generally either does not fit in an image due to size or aesthetic limitations. Even where possible human-visible notice will not be colocated with machine-readable metadata (for bitmap formats currently in use).





Moving Images