Rights Expression Language

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A Rights Expression Language or REL is a machine-processable language used to express intellectual property rights (such as copyright) and other terms and conditions for use over content. RELs can be used as standalone expressions (i.e. metadata usable for search, compatibility tracking) or within a DRM system.

Contents

RELs are expressible in a machine-language (such as XML, RDF, RDF Schema, and JSON). Although RELs may be processed directly, they can also be encountered when embedded as metadata within other documents, such as eBooks, image, audio or video files.

Notable RELs

Notable RELs include:

ccREL
An RDF Schema used by the Creative Commons project to express their licences. [1] [2]
This same vocabulary has also been adopted by the GNU Project to express their General Public License (GPL) in machine-readable form. [3] [4]
W3C Open Digital Rights Language ODRL
The W3C Permissions and Obligations Expression (POE) Working Group has developed the ODRL recommendations for expressing permissions and obligations statements for digital content. [5]
The W3C ODRL Information Model offers a framework for the underlying concepts, entities, and relationships that form the foundational basis for the semantics of ODRL expressions. The aim of the ODRL Information Model is to support flexible Policy expressions by allowing the author to include as much, or as little, expressive detail about the terms and conditions for Asset usage, the Parties involved, and obligations. [6]
The W3C ODRL Vocabulary & Expression describes the potential terms used in ODRL Policy expressions and how to serialise them. The terms form part of the ODRL Ontology and formalise the semantics. The wide set of terms in the vocabulary provides the support for communities to use ODRL as the primary language to express common use cases. [7]
XrML
XrML began with work at Xerox in the 1990s. [8] After passing through several versions and separate projects, it later formed the basis of the REL for MPEG-21. [9]
MPEG-21
Part 5 of this MPEG standard includes a REL. [10]
METSRights
METSRights is an extension schema to the METS packaging metadata standard. [11] [12]

Use of a REL

The function of a REL is to define licences, and to describe these licences in terms of the permissions or restrictions they imply for how the related content may then be used.

"Licence" here may mean either:

Well-known licences

Use of a well-known licence is often chosen for its unambiguous simplicity: GFDL means the same no matter who is using it. Using an existing licences also avoids the problems of licence proliferation. It is also practical to use such a licence, and to check that a project is complying with it, without understanding too much about what detail it entails. Merely knowing that "GFDL is acceptable to this project" and "All resources within this project use GFDL" is sufficient. In that sense, well-known licences are a way to avoid needing to use a REL to model the details of a licence, its name alone is enough. [13]

Despite this, a REL may still be useful with these licences. It provides a machine-processable way to identify the licence in use, avoiding naming issues and potential ambiguities between "Apache License" or "Apache 2.0 Licence". The authors of these licences also require a means to describe their internal details.

Pre-defined licence

These are similar to the well-known licences, in that they're defined before their use and can be applied to many instances of licensing. Their difference is that as they're not well known, it's also necessary to explain what each of them entails, as the user is always likely to be encountering each of them for the first time. A REL provides the means to do this.

Using licensed content within a project now requires evaluation of the statement, "Are there any resources within this project whose licence forbids a condition that the project requires, or requires a condition that the project cannot permit?". These might include a necessary ability to distribute copies of the project afterwards, or a condition for accreditation on a splash screen that might be unacceptable to some projects.

In open source software development, it's also common for projects to create their own licence under their own project name, but for the details of this licence to be a boilerplate copy from a well-known licence, or even a reference to this licence. [14] A REL should support this, providing a means for licences to be defined by sub-classing existing licences and possibly changing their behaviour. Many of these licences are little more than vanity licences, although other dependent projects must still be able to work with them. [15]

Specific licences

These are licences that are created as needed, for specific pieces of content, or specific end users. This is usually so that they may have use-specific conditions attached to them, such as expiry dates. Although these licences might be based on a standard boilerplate, each one is thus unique. Referring to them by name could not work as there's no single, stable name. It's thus necessary to use a REL to express each one in terms of its individual properties.

Examples might include a time-limited contract to watch TV sport for a month, as paid for by an ongoing contract, and to watch this within the home but not to show it within a public bar.

Structure of a REL

A REL may conveniently use an Entity–attribute–value model, as for RDF, to structure its description of a rights model. Such a model [16] expresses itself as lists of:

Entities
Concrete "things" or "classes", e.g.:
The item being licensed.
The licence, particularly when this is either a "well-known" licence (where many Works will use a comparable abstract licence, such as GFDL)
or else an instance of a specific licence, such as content playback rights purchased by one user.
A means to identify the end-user, when the licensing is a specific contract with one person or body, as well as the licensing party.
Rarely stated explicitly, but an important qualifier when there are local legal variations in IP law.
Attributes
"Properties", or aspects of each of these Entities, e.g. for a Licence:
Actions that are either permitted, or forbidden
Some RELs [16] separate these constraints into groups, as the likely values for each are generally disjoint sets (actions that may be sometimes prohibited are rarely compulsory)
Values
Values for these properties, from a pre-defined vocabulary, e.g. the Four Freedoms:

The REL defines sets of members for each of these three groups, and the permitted relations between them. In the example above there may be concepts of Licences, permissions and redistributing copies. Also there may be the relations, A Licence may express prohibitions, and separately Permission may be given to redistribute copies.

Statements may then be made using the REL (these would be outside of the REL itself) such as:

<cc:Licenserdf:about="http://example.org/licenses/distribution/"><cc:licenseClassrdf:resource="https://creativecommons.org/license/"/><dc:title>FooCo'sDistributionPermittedLicence</dc:title><cc:permitsrdf:resource="https://creativecommons.org/ns#Distribution"/></cc:License>

This defines a new abstract licence, one that permits re-distribution of copies. Works may then use this Licence by referring to it,

<p>This web page is licensed under <arel="license"href="http://example.org/licenses/distribution/">FooCo's Distribution Permitted Licence</a>.

Note that although this hypothetical "Distribution permitted" licence has been expressed using the Creative Commons REL, it is not a Creative Commons licence. It merely uses the concepts "License", "permission" and "Distribution". Although it's not one of the Creative Commons licences defined by that project, it does share exact commonality for these terms: "Distribution" has exactly the same meaning and legal definition between them.

The below W3C ODRL example shows an Agreement (License) from the Assigner party for an Asset that can be Displayed by one assignee (user), and another to Print the Asset.

{"@context":{"odrl":"http://www.w3.org/ns/odrl/2/"},"@type":"odrl:Agreement","@id":"http://example.com/policy:4444","target":"http://example.com/asset:5555","assigner":"http://example.com/MyPix:55","permission":[{"assignee":"http://example.com/guest:0001","action":"odrl:display"}],"permission":[{"assignee":"http://example.com/guest:0002","action":"odrl:print"}]}

Interworking between licences

Increasing interest in mashups and collaborative projects creates a demand for combining content, and in licensing technologies that can support this.

The simplest approach is to only combine content under the same well-known licence. This is over-restrictive though, and many compatible licences may permit their content to be combined. It is however difficult to judge this, whether it is permitted and how the resultant content should be licensed. [17] There may still be subtleties when there are overlapping requirements or Copyleft issues. Notably the Creative Commons 'attribution-sharealike' and 'attribution-noncommercial-sharealike' are incompatible. [note 1] [17] [18] [19]

Combining licences is simpler if all of the licences involved may be expressed through the same REL. In that case it's easier to see when a permission or a prohibition applies if they do at least apply to an identical definition of "Distribution". An obvious example of this are the Creative Commons licenses, where a family of licences are all defined in terms of the same REL.

Even if different licences were originally defined through different REL, it may be possible to re-encode a licence simultaneously in another shared REL, making them comparable. GPL has recently been expressed in ccREL, giving this advantage. [3] [4] [note 2]

Difficulties in interworking between licences

Apart from the issues of conflicting requirements (above), there are also technical issues in comparing licences. Many of these are alleviated if the same REL can be used, even if the licences are different.

Semantics

A regular problem with semantic translation between schemas (such as RELs) is in making sure that the meanings of terms are identical. Although the semantic web is beginning to use ontology tools such as OWL to describe meaning, the current state of the art for REL is less advanced than this. Simpler processing, and the potential for expensive litigation otherwise, means that the semantics of RELs must be clearly identical, not just inferred to be so through a reasoner.

The regular problems are in demonstrating the equivalence of classes, properties and instances. For RELs the major problem is for the instances, i.e. the precise definitions of "Distribution", "Share-alike" etc. The classes and properties are usually simple concepts and very similar. Not all RELs support all classes though: some ignore Jurisdiction or even End-user, according to the needs of the market they were developed for.

Implicit pre-conditions

A less-obvious problem in comparing RELs is when they have a differing baseline. [20] [21] The baseline defines the conditions implied by the licence when there are no explicit statements included. Some RELs take the "Everything not permitted is forbidden" approach, others (such as ccREL) use the Berne Convention as their baseline.

Notes

  1. ↑ See Creative Commons#Criticism
  2. ↑ Note that despite the suggestion of Introducing RDF for GNU Licenses, the benefit accrues because GPL is expressed in ccREL (and RDF), not merely in RDF. For licences to become comparable, the REL vocabularies must be shared, not merely the data model.

Related Research Articles

Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines freeware unambiguously; every publisher defines its own rules for the freeware it offers. For instance, modification, redistribution by third parties, and reverse engineering are permitted by some publishers but prohibited by others. Unlike with free and open-source software, which are also often distributed free of charge, the source code for freeware is typically not made available. Freeware may be intended to benefit its producer by, for example, encouraging sales of a more capable version, as in the freemium and shareware business models.

The MIT License is a permissive software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts very limited restriction on reuse and therefore has high license compatibility.

Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has released several copyright licenses, known as Creative Commons licenses, free of charge to the public. These licenses allow authors of creative works to communicate which rights they reserve and which rights they waive for the benefit of recipients or other creators. An easy-to-understand one-page explanation of rights, with associated visual symbols, explains the specifics of each Creative Commons license. Content owners still maintain their copyright, but Creative Commons licenses give standard releases that replace the individual negotiations for specific rights between copyright owner (licensor) and licensee, that are necessary under an "all rights reserved" copyright management.

The Resource Description Framework (RDF) is a World Wide Web Consortium (W3C) standard originally designed as a data model for metadata. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of syntax notations and data serialization formats, with Turtle currently being the most widely used notation.

<span class="mw-page-title-main">Creative Commons license</span> Copyright license for free use of a work

A Creative Commons (CC) license is one of several public copyright licenses that enable the free distribution of an otherwise copyrighted "work". A CC license is used when an author wants to give other people the right to share, use, and build upon a work that the author has created. CC provides an author flexibility and protects the people who use or redistribute an author's work from concerns of copyright infringement as long as they abide by the conditions that are specified in the license by which the author distributes the work.

<span class="mw-page-title-main">Free Art License</span> Type of free content license

The Free Art License (FAL) is a copyleft license that grants the right to freely copy, distribute, and transform creative works.

The Open Digital Rights Language (ODRL) is a policy expression language that provides a flexible and interoperable information model, vocabulary, and encoding mechanisms for representing statements about the usage of content and services. ODRL became an endorsed W3C Recommendation in 2018.

RDFa or Resource Description Framework in Attributes is a W3C Recommendation that adds a set of attribute-level extensions to HTML, XHTML and various XML-based document types for embedding rich metadata within Web documents. The Resource Description Framework (RDF) data-model mapping enables its use for embedding RDF subject-predicate-object expressions within XHTML documents. It also enables the extraction of RDF model triples by compliant user agents.

This comparison only covers software licenses which have a linked Wikipedia article for details and which are approved by at least one of the following expert groups: the Free Software Foundation, the Open Source Initiative, the Debian Project and the Fedora Project. For a list of licenses not specifically intended for software, see List of free-content licences.

License compatibility is a legal framework that allows for pieces of software with different software licenses to be distributed together. The need for such a framework arises because the different licenses can contain contradictory requirements, rendering it impossible to legally combine source code from separately-licensed software in order to create and publish a new program. Proprietary licenses are generally program-specific and incompatible; authors must negotiate to combine code. Copyleft licenses are commonly deliberately incompatible with proprietary licenses, in order to prevent copyleft software from being re-licensed under a proprietary license, turning it into proprietary software. Many copyleft licenses explicitly allow relicensing under some other copyleft licenses. Permissive licenses are compatible with everything, including proprietary licenses; there is thus no guarantee that all derived works will remain under a permissive license.

<span class="mw-page-title-main">Free content</span> Creative work with few or no restrictions on how it may be used

Free content, libre content, libre information, or free information is any kind of functional work, work of art, or other creative content that meets the definition of a free cultural work, meaning "works or expressions which can be freely studied, applied, copied and/or modified, by anyone, for any purpose."

<span class="mw-page-title-main">Free-software license</span> License allowing software modification and redistribution

A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that software. These actions are usually prohibited by copyright law, but the rights-holder of a piece of software can remove these restrictions by accompanying the software with a software license which grants the recipient these rights. Software using such a license is free software as conferred by the copyright holder. Free-software licenses are applied to software in source code and also binary object-code form, as the copyright law recognizes both forms.

<span class="mw-page-title-main">Copyleft</span> Practice of mandating free use in all derivatives of a work

Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, freedoms refers to the use of the work for any purpose, and the ability to modify, copy, share, and redistribute the work, with or without a fee. Licenses which implement copyleft can be used to maintain copyright conditions for works ranging from computer software, to documents, art, scientific discoveries and even certain patents.

<span class="mw-page-title-main">GNU General Public License</span> Series of free software licenses

The GNU General Public License is a series of widely used free software licenses or copyleft that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general use and was originally written by Richard Stallman, the founder of the Free Software Foundation (FSF), for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. These GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the Lesser General Public License and even further distinct from the more widely used permissive software licenses BSD, MIT, and Apache.

<span class="mw-page-title-main">GNU Free Documentation License</span> Copyleft license primarily for free software documentation

The GNU Free Documentation License is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, and modify a work and requires all copies and derivatives to be available under the same license. Copies may also be sold commercially, but, if produced in larger quantities, the original document or source code must be made available to the work's recipient.

Creative Commons Rights Expression Language (ccREL) is a proposed Rights Expression Language (REL) for descriptive metadata to be appended to media that is licensed under any of the Creative Commons licenses. According to the draft submitted to the W3C, it is to come in the forms of RDFa for (x)HTML pages and XMP for standalone media.

The Publishing Requirements for Industry Standard Metadata (PRISM) for the Internet, computing, and computer science, is a specification that defines a set of XML metadata vocabularies for syndicating, aggregating, post-processing and multi-purposing content.

XHTML+RDFa is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. XHTML+RDFa is one of the techniques used to develop Semantic Web content by embedding rich semantic markup. Version 1.1 of the language is a superset of XHTML 1.1, integrating the attributes according to RDFa Core 1.1. In other words, it is an RDFa support through XHTML Modularization.

A free license or open license is a license which allows others to reuse another creator’s work as they wish. Without a special license, these uses are normally prohibited by copyright, patent or commercial license. Most free licenses are worldwide, royalty-free, non-exclusive, and perpetual. Free licenses are often the basis of crowdsourcing and crowdfunding projects.

Software relicensing is applied in open-source software development when software licenses of software modules are incompatible and are required to be compatible for a greater combined work. Licenses applied to software as copyrightable works, in source code as binary form, can contain contradictory clauses. These requirements can make it impossible to combine source code or content of several software works to create a new combined one.

References

  1. ↑ "ccREL: The Creative Commons Rights Expression Language" (PDF). Creative Commons. 3 March 2008.
  2. ↑ "10: ccREL: The Creative Commons Rights Expression Language" (PDF). The Digital Public Domain: Foundations for an Open Culture. 2012.
  3. 1 2 "Introducing RDF for GNU Licenses". Free Software Foundation.
  4. 1 2 "GPL in RDF" (RDF). Free Software Foundation.
  5. ↑ "Permissions and Obligations Expression Working Group". www.w3.org.
  6. ↑ "ODRL Information Model 2.2". www.w3.org.
  7. ↑ "ODRL Vocabulary & Expression 2.2". www.w3.org.
  8. ↑ "XrML... eXtensible rights Markup Language". www.xrml.org.
  9. ↑ "The MPEG-21 Rights Expression Language" (PDF). Rightscom. Archived from the original (PDF) on November 8, 2006.
  10. ↑ MPEG. "Part 5: Rights Expression Language". Archived from the original on 2009-07-05.
  11. ↑ Nancy J. Hoebelheinrich (Stanford University Libraries). "METSRights Schema". Library of Congress .
  12. ↑ "METSRights examples". Library of Congress.
  13. ↑ Ed Burnette (2006-11-02). "Google says no to license proliferation". ZDNet . Archived from the original on 2007-02-24.
  14. ↑ Make Your Open Source Software GPL-Compatible. Or Else., D. Wheeler (2014)
  15. ↑ David A. Wheeler (20 August 2008). "FLOSS License Proliferation: Still a problem".
  16. 1 2 "Can I combine two different Creative Commons licensed works? Can I combine a Creative Commons licensed work with another non-CC licensed work?". FAQ. Creative Commons. Retrieved 16 Sep 2009.
  17. ↑ "Creative Commons — Attribution-ShareAlike 3.0 Unported — CC BY-SA 3.0".
  18. ↑ "Creative Commons — Attribution-NonCommercial-ShareAlike 3.0 Unported — CC BY-NC-SA 3.0".
  19. ↑ "ccREL: The Creative Commons Rights Expression Language". W3C Member Submission. 1 May 2008.
  20. ↑ Nathan Yergler. "How to negate cc:permits, cc:prohibits, cc:requires?". cc-metadata mailing list.
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