OPML
Encyclopedia
OPML is an XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 format for outlines (defined as "a tree, where each node contains a set of named attributes with string values"). Originally developed by Radio UserLand
Radio UserLand
Radio UserLand is a software package from UserLand Software, first released in 2000, which includes not only a client-side blogging tool but also an RSS aggregator, an outliner and a scripting language.-Features:...

 as a native file format for an outliner
Outliner
An outliner is a computer program that allows text to be organized into discrete sections that are related in a tree structure or hierarchy. Text may be collapsed into a node, or expanded and edited....

 application, it has since been adopted for other uses, the most common being to exchange lists of web feeds between web feed aggregators.

The OPML specification defines an outline as a hierarchical, ordered list of arbitrary elements. The specification is fairly open which makes it suitable for many types of list data.

Shortcomings

  1. The RFC 822 date format is considered obsolete, and amongst other things permits the representation of years as two digits. (RFC 822 has been superseded by RFC 2822 then RFC 5322.) In general, date and time formats should be represented according to RFC 3339.
  2. Because "expansionState" is recorded independently of the outline elements:
    • The expansion state of the children of collapsed nodes cannot be stored
    • When an outline element is expanded, collapsed, added, deleted or moved, the expansion state of all elements below it must be recalculated
  3. Due to the arbitrary nature of the "type" attribute, and the acceptance of arbitrary attributes on "outline" elements, interoperability of OPML documents relies almost entirely on the undocumented conventions of content producers.
  4. MIME types aren't clear; text/xml usually merely identifies the document as having XML content, while text/x-opml does not specify that the document is XML since it lacks the +xml suffix (see XML and MIME
    XML and MIME
    There are two MIME assignments for XML data. These are:*application/xml *text/xml Because of the wide variety of documents that can be expressed using an XML syntax, additional MIME types are needed to differentiate between languages...

    ).
  5. Exporting your data from an OPML file to another format can't be done without coding: no free tools are available to convert an OPML file to HTML, and browsers such as Firefox and Internet Explorer cannot display an OPML file.

Validation

Dave Winer
Dave Winer
Dave Winer is an American software developer, entrepreneur and writer in New York City. Winer is noted for his contributions to outliners, scripting, content management, and web services, as well as blogging and podcasting...

 has made a request for comments on a proposal for validating OPML and released a beta OPML validator.

Katy Ginger from DLESE has published an XML Schema Document for validating OPML 2.0. There is also a DTD available for OPML 1.0.

Example OPML documents


Alternative specifications

Alternative specifications have been proposed, notably these include OML
OML
OML is an XML format for outlines. It was originally proposed by Ray Grieselhuber. The specification is designed to build upon the concepts found in OPML, with the goal of fixing some of its limitations....

, XOXO
XOXO
XOXO is an XML microformat for outlines built on top of XHTML. Developed by several authors as an attempt to reuse XHTML building blocks instead of inventing unnecessary new XML elements/attributes, XOXO is based on existing conventions for publishing outlines, lists, and blogrolls on the Web.The...

 and XBEL
XBEL
XBEL, or the XML Bookmark Exchange Language, is an open XML standard for sharing Internet URIs, also known as bookmarks ....

.

See also

  • DataPortability
    DataPortability
    Data portability is the ability for people to reuse their data across interoperable applications - the ability for people to be able to control their identity, media and other forms of personal data...

  • Dave Winer
    Dave Winer
    Dave Winer is an American software developer, entrepreneur and writer in New York City. Winer is noted for his contributions to outliners, scripting, content management, and web services, as well as blogging and podcasting...

  • List of content syndication markup languages
  • XOXO
    XOXO
    XOXO is an XML microformat for outlines built on top of XHTML. Developed by several authors as an attempt to reuse XHTML building blocks instead of inventing unnecessary new XML elements/attributes, XOXO is based on existing conventions for publishing outlines, lists, and blogrolls on the Web.The...

     - Extensible Open XHTML Outlines
  • XBEL
    XBEL
    XBEL, or the XML Bookmark Exchange Language, is an open XML standard for sharing Internet URIs, also known as bookmarks ....

     - XML Bookmark Exchange Language
  • APML - Attention Profiling Mark-up Language
  • Feed icon
    Feed icon
    The Feed icon is for indicating that a web feed is available on a web page. It was originally invented for the use of RSS, but it is also common for Atom and other web feeds now....

  • Share icon
    Share icon
    The Open Share Icon computer icon designed to help users easily identify shareable content. Introduced by Shareaholic and hence also often referred to as the "Shareaholic Icon", this icon is available for use by others under the Creative Commons Attribution-Share Alike 3.0 Unported License...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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