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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 everything 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

Key Comment
version Same as RCS version
date integer, unix time, seconds since start 1970
author last to change topic, is the REMOTE_USER
format Format of this topic, will be used for automatic format conversion

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"}%

Key Comment
from Full name, i.e., web.topic
to Full name, i.e., web.topic
by Who did it, is the REMOTE_USER, not WikiName
date integer, unix time, seconds since start 1970

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

Key Comment
name The topic from which this was created, typically when clicking on a red-link, or by filling out a form. Normally just TopicName, but it can be a full Web.TopicName format if the parent is in a different Web.

META:FILEATTACHMENT

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

Extra fields that are added if an attachment is moved:

Key Comment
movedfrom full topic name - web.topic
movedby the REMOTE_USER, not WikiName
movedto full topic name - web.topic
moveddate integer, unix time, seconds since start 1970

META:FORM

Key Comment
name A topic name - the topic represents one of the TWikiForms. Can optionally include the web name (i.e., web.topic), but doesn't normally

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.

Key Name
name Ties to entry in TWikiForms template, is title with all bar alphanumerics and . removed
title Full text from TWikiForms template
value Value user has supplied via form

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:

Variable usage: Comment:
%META{"form"}% Show form data, see TWikiForms.
%META{"formfield"}% Show form field value. Parameter: name="field_name". Example:
%META{ "formfield" name="TopicClassification" }%
%META{"attachments"}% Show attachments, except for hidden ones. Options:
all="on": Show all attachments, including hidden ones.
%META{"moved"}% Details of any topic moves.
%META{"parent"}% Show topic parent. Options:
dontrecurse="on": By default recurses up tree, at some cost.
nowebhome="on": Suppress WebHome.
prefix="...": Prefix for parents, only if there are parents, default "".
suffix="...": Suffix, only appears if there are parents, default "".
separator="...": Separator between parents, default is " > ".

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

Related Topics: DeveloperDocumentationCategory, UserDocumentationCategory

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