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[[Category:Developer]]
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{{Software Project
[[Category:Metadata]]
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|Description=Low-level license metadata integration for applications.
[[Category:Desktop]]
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|Bug tracker=http://code.creativecommons.org/issues/issue?status=-1,1,2,3,4,5,6,7&@sort=-activity&@search_text=&@dispname=liblicense&@filter=status,project&@group=priority&project=4&@columns=id,activity,title,creator,assignedto,status&@pagesize=50&@startwith=0
[[Category:Labs]]
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|Code repository=http://code.creativecommons.org/viewgit/liblicense.git/
[[Category:Tools]]
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|Mailing list=http://lists.ibiblio.org/mailman/listinfo/cc-devel
[[Category:Specification]]
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}}
[[Category:Operating System]]
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== What is liblicense? ==
[[Category:Technology]]
 
A library for managing license metadata, in particular CC licensing information.
 
 
 
The idea of this library started out on the [[IRC]] channel, in a discussion on how to best help boost the community of software
 
developers working with things related to CC - mostly the metadata format.
 
 
 
Basically, the idea is to write a portable C library that manages metadata for CC licenses, and a bunch of other licenses of interest to the community.
 
 
 
The library will produce licensing information based on the specifications of calling libraries and programs. In addition to generating text for specific licenses, it will also allow an application to enumerate which licenses are currently available and provide descriptive text for each license, and for license features. It should also provide an easy way to specify "verify at" URLs.
 
  
The benefit of this library is that applications linking to it can correctly offer licensing choices, and these choices can be transparently updated through package managers as license versions are updated. Human readable descriptions will also be internationalized, preferably using the same .po files used by the CC web site. Hence liblicense will take advantage of package updating and i18n systems to allow applications to always provide c
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liblicense provides a straight-forward way for developers to build license-aware applications. liblicense utilizes a pluggable module system for reading and writing metadata from specific file types, allowing extensibility for specific content types.
current and correct licensing choices and license text.
 
  
Part of the project is also to provide wrappers for the library for other languages, and to help external developers add metadata support to their projects. A good start will probably be to wrap the library for Python, and use it for ccpublisher.
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* For a brief introduction video, check [http://blip.tv/file/1142312/ Asheesh Laroia talking about liblicense]
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* To see '''liblicense in action''' take a look at [[License tagger]], the cross platform file metadata editor.
  
We will also integrate a module system so that libraries can be used to embed and extract metadata in/from common formats.
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== Features ==
  
As liblicense itself deals only with text strings, we can also make GUI libraries to provide dialogs which present these strings to the user in desktop or web applications. This layering ensures that such dialogs present consistent licensing choices.
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* Extract and write license information for files
 +
* Supports enumeration of available licenses
 +
* Wraps internationalized license information for Creative Commons licenses
 +
* Bindings for dynamic languages (currently Python and Ruby)
 +
* Extensible support for file types using module system
 +
* No specific GUI library dependency allows applications to build the graphical chooser most appropriate for their platform.
  
== System Overview ==
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== Future Improvements ==
  
=== Purpose ===
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* Supports [[WebStatement|verification]] URLs for metadata verification
To provide a simple way for developers to make their applications license aware.  Additionally, supplemental modules aim to provide a method for users to track licenses of files on their system.  This project complements [[Companion File metadata specification]] and [[Tracker CC Indexing]].
 
  
=== Architecture ===
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== Architecture ==
 
[[Image:System_architecture.png]]
 
[[Image:System_architecture.png]]
  
[[Image:System_architecture.svg | svg version]]
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[[:Image:System_architecture.svg|Liblicense Architecture - SVG]]
  
=== Implementation ===
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== Bindings ==
This library will be implemented in C to provide maximum portability.
 
  
=== Interface ===
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* [[Liblicense/Python|Python]]
* module_wrangler
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* [[Liblicense/Ruby|Ruby]]
** get_config_modules() - ''returns a null terminates list of available config modules.''
 
** get_io_modules() - ''returns a null terminates list of available io modules.''
 
** get_module_symbol(module,symbol) - ''returns the requested symbol.''
 
** module_in_use(module) - ''returns whether the support system is in use.  If its not it will not work.''
 
** io_module_mime_types(module0 - ''returns a null-terminated list of the supported mime-types.''
 
* read_license
 
** read(filename) - ''returns the uri of the license of the given file.''
 
** module_read(filename,module) - ''returns the uri of the license of the given file while using the given module.''
 
* write_license
 
** write(filename,uri) - ''writes the given license to the given file using all applicable modules.''
 
** module_write(filename,module,uri) - ''writes the given license to the given file using the given module.''
 
* system_default
 
** set_default(uri)
 
** get_default()
 
** default_engines() - ''returns a null-terminated list of the default engines in use.''
 
* system_licenses
 
** get_jurisdiction(uri) - ''returns the jurisdiction for the given license.''
 
** get_locales(uri) – ''returns the available locales for the given license.''
 
** get_name(uri) – ''returns the name of the license.''
 
** get_version(uri) – ''returns the version of the license.''
 
** get_notification(uri[,url]) - ''returns the notification string for the given url with an option to provide a verification url.''
 
** verify_uri(uri) - ''returns whether or not the given uri is recognized by the system.''
 
** get_all_licenses() - ''returns a null-terminated list of all general license uris available for new works.''
 
** get_licenses_in_juris(juris_t) - ''returns a null-terminated list of all general licenses in a family.''
 
  
=== Data Structure ===
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== Media ==
* Data Types (informal)
 
** uri
 
** name
 
** notification
 
** deed
 
** sampling
 
  
=== Config Modules ===
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See [[Operating System Mockups]] for ideas on how '''liblicense''' could be integrated into various platforms.
* '''in_use'''() - returns whether or not the corresponding config system exists on the computer
 
* '''get'''() - returns the current default license uri
 
* '''set'''(uri) - sets the default license uri and returns 0 upon success (non-zero for errors)
 
  
=== I/O Modules ===
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== Download ==
* '''mime_types''' - null terminated list of handled mime-types (all indicates external storage method which works for any file)
 
* '''read'''(filename) - returns the license uri for the given file (embedded license takes precedence)
 
* '''write'''(filename,uri) - writes the license uri for the given file
 
  
=== Bindings ===
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* [http://mirrors.creativecommons.org/software/liblicense/liblicense-0.8.1.tar.gz Latest Release tar.gz]
*Python
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* Debian and Ubuntu [http://mirrors.creativecommons.org/packages/ repositories].
 +
* Read the [[Liblicense tutorial| tutorial]].
  
== License Files (.rdf) ==
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=== Developers: Using git ===
=== Attributes ===
 
  
* cc:license
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If you want to check out the source code and develop on it, use this command:
** about
 
** permits
 
** requires
 
** prohibits
 
* dc:title - The human readable name of the license.
 
* dc:description - Description of the license.
 
* dc:coverage - The jurisdiction of the license. (country code from [http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html ISO3166])
 
* dc:language - The language of the license. (language code under [http://www.ietf.org/rfc/rfc3066.txt RFC3066])
 
* dc:relation
 
** hasVersion - version number
 
** isReplacedBy - indicates retired license ([http://www.ietf.org/rfc/rfc2396.txt URI])
 
** isBasedOn - indicates ported version ([http://www.ietf.org/rfc/rfc2396.txt URI])
 
* dc:type - always "License"
 
* dc:creator
 
* dc:publisher
 
* dc:identifier - URI of license ([http://www.ietf.org/rfc/rfc2396.txt URI])
 
  
=== Example ===
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git clone git://code.creativecommons.org/liblicense.git
<pre><rdf:RDF
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git submodule init
  xmlns="http://creativecommons.org/ns#"
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  git submodule update
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 
  xmlns:dc="http://purl.org/dc/elements/1.1/"
 
  xmlns:dcq="http://purl.org/dc/terms/"
 
>
 
  <rdf:Description rdf:about="http://creativecommons.org/licenses/by-nd/2.0/za/">
 
    <dc:title>Creative Commons Attribution No Derivatives</dc:title>
 
    <dc:description>This license allows for redistribution, commercial and non-commercial,
 
  as long as it is passed along unchanged and in whole, with credit to you.</dc:description>
 
    <dc:coverage>
 
        <dcq:ISO3166>
 
            <rdf:value>za</rdf:value>
 
        </dcq:ISO3166>
 
    </dc:coverage>
 
    <dc:language>
 
        <dcq:RFC3066>
 
            <rdf:value>en</rdf:value>
 
        </dcq:RFC3066>
 
    </dc:language>
 
    <dc:hasVersion>2.0</dc:hasVersion>
 
    <dc:isReplacedBy>
 
        <dcq:URI>
 
            <rdf:value>http://creativecommons.org/licenses/by-nd/2.5/za/</rdf:value>
 
        </dcq:URI>
 
    </dc:isReplacedBy>
 
    <dc:isBasedOn>
 
        <dcq:URI>
 
            <rdf:value>http://creativecommons.org/licenses/by-nd/2.5/</rdf:value>
 
        </dcq:URI>
 
    </dc:isBasedOn>
 
    <dc:type>License</dc:type>
 
    <dc:creator>iCommons</dc:creator>
 
    <dc:publisher>Creative Commons</dc:publisher>
 
    <dc:identifier>http://creativecommons.org/licenses/by-nd/2.0/za/</dc:identifier>
 
  
    <rdf:type rdf:resource="http://creativecommons.org/ns#License"/>
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That should give you a working copy you can commit to. In case you wonder: the latter two commandsfill the directories
    <permits rdf:resource="http://creativecommons.org/ns#Distribution"/>
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* icons/jurisdictions
    <permits rdf:resource="http://creativecommons.org/ns#Reproduction"/>
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* license.rdf
    <requires rdf:resource="http://creativecommons.org/ns#Attribution"/>
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* licenses
    <requires rdf:resource="http://creativecommons.org/ns#Notice"/>
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with content from external repositories similar to ''svn:externals'' for Subversion.
  </rdf:Description>
 
</rdf:RDF></pre>
 
  
=== Example (i18n) ===
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== More Information ==
<pre><rdf:RDF
 
  xmlns="http://creativecommons.org/ns#"
 
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 
  xmlns:dc="http://purl.org/dc/elements/1.1/"
 
  xmlns:dcq="http://purl.org/dc/terms/"
 
>
 
  <rdf:Description rdf:about="http://creativecommons.org/licenses/by-nd/2.0/">
 
    <dc:title>
 
        <rdf:Alt>
 
            <rdf:li xml:lang="x-default">Creative Commons Attribution No Derivatives</rdf:li>
 
            <rdf:li xml:lang="es-cl">Creative Commons Atribución-SinDerivadas</rdf:li>
 
        </rdf:Alt>
 
    </dc:title>
 
    <dc:description>
 
        <rdf:Alt>
 
            <rdf:li xml:lang="x-default">This license allows for redistribution, commercial and non-commercial,
 
as long as it is passed along unchanged and in whole, with credit to you.</rdf:li>
 
        </rdf:Alt>
 
    </dc:description>
 
    <dc:coverage>
 
        <dcq:ISO3166>
 
            <rdf:value>us</rdf:value>
 
        </dcq:ISO3166>
 
    </dc:coverage>
 
    <dc:language>
 
        <dcq:RFC3066>
 
            <rdf:value>en</rdf:value>
 
        </dcq:RFC3066>
 
    </dc:language>
 
    <dc:hasVersion>2.0</dc:hasVersion>
 
    <dc:isReplacedBy>
 
        <dcq:URI>
 
            <rdf:value>http://creativecommons.org/licenses/by-nd/2.5/</rdf:value>
 
        </dcq:URI>
 
    </dc:isReplacedBy>
 
    <dc:type>License</dc:type>
 
    <dc:creator>Creative Commons</dc:creator>
 
    <dc:publisher>Creative Commons</dc:publisher>
 
    <dc:identifier>http://creativecommons.org/licenses/by-nd/2.0/</dc:identifier>
 
  
    <rdf:type rdf:resource="http://creativecommons.org/ns#License"/>
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* [[Liblicense/Releases|Release History]] and [[Liblicense/Roadmap|Roadmap]]
    <permits rdf:resource="http://creativecommons.org/ns#Distribution"/>
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* [[Liblicense/Desktop_Integration|Desktop Integration]]
    <permits rdf:resource="http://creativecommons.org/ns#Reproduction"/>
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* [[Liblicense/Screenshots|Screenshots]]
    <requires rdf:resource="http://creativecommons.org/ns#Attribution"/>
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* [[License RDF|RDF Reference]]
    <requires rdf:resource="http://creativecommons.org/ns#Notice"/>
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* [[Liblicense/Metadata_Table|File Metadata Information]]
  </rdf:Description>
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* [http://code.creativecommons.org/doc/liblicense/ Library Documentation] (generated from source)
</rdf:RDF></pre>
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* [[Buildbot]] helps test out liblicense on various platforms.
  
== Frontends ==
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== See Also ==
  
See [[Desktop Integration]]
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* [[Companion File metadata specification]]  
 +
* [[Tracker CC Indexing]] - also there is a great chart showing progress on reading/writing different filetypes (copied above).
  
=== Gnome Summit Discussion ===
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{{Challenge Enabled}}
  
At the Gnome Summit we explored adding CC licensing to various Gnome applications.  Application developers appeared to have a few needs:
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[[Category:Developer]]
 
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[[Category:Metadata]]
* They want to display the appropriate icon (or other) for a particular license.  For instance, AbiWord could display a small icon representing license status in the tool bar.  Music players could display the icon in the controls area.  A music streaming app might want to play a 5 second "Now entering the Creative Commons" chime (much like radio station identification, but for licenses).
+
[[Category:Desktop]]
* They want to allow the user to easily select a license.  This would probably be a wizard that asks the user questions and tries to select the most appropriate license from all that it knows about.  Much like a file selection dialog, but navigating licenses instead of your file system.
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[[Category:Labs]]
 
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[[Category:Tools]]
A low-level liblicense could handle XML parsing required.  It would allow the client to determine the questions that need to be asked to select a license, and to download any icons, blurbs, etc for all known license types.
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[[Category:Specification]]
 
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[[Category:Operating System]]
The low-level library solves the first problem above, but not the second.  It's still too difficult to ask the user to select a license.  Layered on top of the low-level library would be any number of high level libraries that would convert the textual questions into GUI widgets and present them using the appropriate toolkit (GTK+ / KDE / Cocoa / Win32 / etc).  This way, adding license awareness to an application should be as easy as "license=SFGetLicense(); saveDocument(license)".
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[[Category:Technology]]
 
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[[Category:Integration]]
== Timeline ==
 
=== 6/18 ===
 
* Finalize liblicense API.
 
 
 
=== 6/25 ===
 
* Write liblicense.
 
* Stub config and IO modules.
 
 
 
=== 7/2 ===
 
* liblicense python bindings.
 
 
 
=== 7/9 ===
 
* Gconf config module.
 
* Nautilus IO module.
 
 
 
=== 7/16 ===
 
* Nautilus GUI frontend.
 
* Gnome control panel frontend.
 
 
 
=== 7/23 ===
 
* Sugar Journal backend.
 
* Sugar frontend.
 
 
 
=== 7/30 ===
 
* Bug hunting.
 
* Frontend polishing.
 
 
 
=== 8/6 ===
 
{{stub}}
 
 
 
=== 8/13 ===
 
{{stub}}
 
  
=== 8/20 ===
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__NOTOC__
{{stub}}
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{{lowercase}}

Latest revision as of 20:53, 23 September 2015

Description of Software Low-level license metadata integration for applications.
Bug Tracker Link to Bug Tracker
Code Repository Link to Code repository
Mailing List Link to Mailing list

What is liblicense?

liblicense provides a straight-forward way for developers to build license-aware applications. liblicense utilizes a pluggable module system for reading and writing metadata from specific file types, allowing extensibility for specific content types.

Features

  • Extract and write license information for files
  • Supports enumeration of available licenses
  • Wraps internationalized license information for Creative Commons licenses
  • Bindings for dynamic languages (currently Python and Ruby)
  • Extensible support for file types using module system
  • No specific GUI library dependency allows applications to build the graphical chooser most appropriate for their platform.

Future Improvements

Architecture

System architecture.png

Liblicense Architecture - SVG

Bindings

Media

See Operating System Mockups for ideas on how liblicense could be integrated into various platforms.

Download

Developers: Using git

If you want to check out the source code and develop on it, use this command:

git clone git://code.creativecommons.org/liblicense.git
git submodule init
git submodule update

That should give you a working copy you can commit to. In case you wonder: the latter two commandsfill the directories

  • icons/jurisdictions
  • license.rdf
  • licenses

with content from external repositories similar to svn:externals for Subversion.

More Information

See Also


Liblicense
Have an idea about this page? Want to help build the CC ecosystem? Check out the challenges related to Liblicense, or add one of your own below.
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