TWiki Meta Data

Additional topic data, program-generated or from TWikiForms, is stored embedded in the topic text using META: tags

Overview

By default, TWiki stores topics in files on disk, in a really simple and obvious directory structure. The big advantage of this approach is that it makes it really easy to manipulate topics from outside TWiki, and is also very safe; there are no complex binary indexes to maintain, and moving a topic from one TWiki to another is as simple as copying a couple of text files.

To keep eveything together in one place, TWiki uses a simple method for embedding additional data (program-generated or from TWikiForms) in topics. It does this using META: tags.

META: data includes program-generated info like FileAttachment and topic movement data, and user-defined TWikiForms info.

Meta Data Syntax

• Format is the same as in TWikiVariables, 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.

• Values in meta-data are URL encoded so that characters such as \n can be stored.

Example of Format

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

Meta Data Specifications

The current version of Meta Data is 1.0, with support for the following variables.

META:TOPICINFO

META:TOPICMOVED

This is optional, exists if topic has ever been moved. If a topic is moved more than once, only the most recent META: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.

META:TOPICPARENT

META:FILEATTACHMENT

Key	Comment
comment	As supplied when file uploaded
path	Full path file was loaded from
attr	h if hidden, optional
size	In bytes
date	integer, unix time, seconds since start 1970
name	Name of file, no path. Must be unique within topic
version	Same as RCS revision
user	the REMOTE_USER, not WikiName

Extra fields that are added if an attachment is moved:

META:FORM

META:FIELD

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

Recommended Sequence

There is no absolute need for Meta Data variables to be listed in a specific order within a topic, but it makes sense to do so a couple of good reasons:

• form fields remain in the order they are defined
• the diff function output appears in a logical order

The recommended sequence is:

• META:TOPICINFO
• META:TOPICPARENT (optional)
• text of topic
• META:TOPICMOVED (optional)
• META:FILEATTACHMENT (0 or more entries)
• META:FORM (optional)
• META: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 (i.e., 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

Rendering Meta Data

Meta Data is rendered with the %META% variable. This is mostly used in the view, preview and edit scripts.

You can render form fields in topic text by using the FORMFIELD variable. Example:
%FORMFIELD{"TopicClassification"}%
For details, see VarFORMFIELD.

Current support covers:

Note: SEARCH can also be used to render meta data, see examples in FormattedSearch and SearchPatternCookbook.

Related Topics: DeveloperDocumentationCategory, UserDocumentationCategory