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TWiki Meta Data

What is Meta Data in TWiki?

What, indeed!

Defining Meta Data Variables

See Meta Data Rendering for variables used to display meta data.

Current version: 1.0

Syntax

• Format is as for [[TWikiDocumentation#TWiki_Variables, except all fields have a key.
  • %META:<type>{key1="value1" [key2="value2" [...]]}%
• Order of fields within the meta variables is not defined, except that if there is a field with key name, this appears first for easier searching (note the order of the variables themselves is defined)
• Each meta variable is on one line
• '\n' is represented in values by %_N_ and '"' by %_Q_%

Example of Format

%<nop>META:TOPICINFO{version="1.6" date="976762663" author="PeterThoeny" format="1.0"}%
   text of the topic
%<nop>META:TOPICMOVED{from="Codev.OldName" to="CoDev.NewName"
   by="JohnTalintyre" date="976762680"}%
%<nop>META:TOPICPARENT{name="NavigationByTopicContext"}%
%<nop>META:FILEATTACHMENT{name="Sample.txt" version="1.3" ... }%
%<nop>META:FILEATTACHMENT{name="Smile.gif" version="1.1" ... }%
%<nop>META:FORM{name="WebFormTemplate"}%
%<nop>META:FIELD{name="OperatingSystem" value="OsWin"}%
%<nop>META:FIELD{name="TopicClassification" value="PublicFAQ"}%

Specifications

TOPICINFO

TOPICMOVED

This is optional, exists if topic has ever been moved. If a topic is moved more than once, only the most recent TOPICMOVED meta variable exists in the topic, older ones are to be found in the rcs history.

%META:TOPICMOVED{from="Codev.OldName" to="CoDev.NewName" by="talintj" date="976762680"}%

Notes:

• at present version number is not supported directly, it can be inferred from the RCS history.
• there is only one META:TOPICMOVED in a topic, older move information can be found in the RCS history.

TOPICPARENT

FILEATTACHMENT

Extra field that are added if an attachment is moved:

FORM

FIELD

Should only be present if there is a FORM entry. Note that this data is used when viewing a topic, the form template definition is not read.

Recommended Sequence

There no absolute need for meta data variables to be in a specific order, however, it does for the following reasons:

• Keep (form) fields in the order they are defined
• Allow diff command to give output in a logically sensible order

These could be done in other ways, but this adds complexity

• Order fields - definition could be read on each rendering (expensive)
• Diff - render data before doing diff, has something to offer, but not likely to be available for next TWiki release

So the order is:

• TOPICINFO
• text of topic
• TOPICMOVED - optional
• TOPICPARENT - optional
• FILEATTACHMENT - 0 or more entries
• FORM - optional
• FIELD - 0 or more entries (FORM required)

Viewing Meta Data in Page Source

When viewing a topic the Raw Text link can be clicked to show the text of a topic (ie: as seen when editing). This is done by adding raw=on to URL. raw=debug shows the meta data as well as the topic data, ex: debug view for this topic

Future Support for Plugins

There is currently no support for meta data for Plugins. However, the format is readily extendable and the Meta.pm code that supports the format needs only minor alteration.

Rendering Meta Data

Various types of meta data can be stored in topics. The data is rendered using the %META% variable. This is mostly used in the view, preview and edit scripts.

Current support is fairly basic:

• Future Development: There are numerous development directions and specific features to consider. A couple of obvious possibilities:
  • Rendering to formats other than tables: bullet lists, formatted body text;
  • Specifying templates to be used for rendering.

-- JohnTalintyre - 29 Aug 2001