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TitleWiki Links Through XPATH, including SubPages support
Date23-May-2006 22:17:36 EEST
JSPWiki version
Submitter DF
Idea CategoryGenericIdea
Reference
Idea StatusNewIdea

Wiki Link syntax extended with XPATH#

See also XPath

This page describes an approach to extend the wiki [link syntax] to powerful expressions based on XPATH and JSR-170. It would also allow to add subpages to JSPWiki.

Example of current syntax :

   [SandBox]                            =>yield link to wiki page
   [SandBox/attach.jpg]                 =>yield link to attachment
Example of extended Wiki Link syntax :
   [SandBox/w:properties/variableX]     =>yield value of wiki variable
   [SandBox/w:versions/v123]            =>yield link to wiki page version
   [SandBox/w:versions/v123/attach.jpg] =>yield link to attachment

   [SandBox/@variableX]                 =>yield value of wiki variable
   [SandBox/v123/attach.jpg]            =>yield link to attachment

Normally, the wiki link syntax returns a single result, being a link to a wiki page or attachment. From the previous examples, you can see that it is also possible to return the value of page variables as well as links to page versions different from the latest version.

Additionally, XPATH expressions will allow to return multiple results, separated by a space.

   [SandBox/w:to]                       =>yield all referred-to page links
   [SandBox/w:from]                     =>yield all referred-from page links
   [SandBox/w:versions]                 =>yield links to all versions of SandBox
   [SandBox/w:properties]               =>yield all variables (how? name=value)
   [SandBox/w:attachments]              =>yield all attachment links

Wiki Metadata XML model#

A Wiki Link can be written be means of an XPath expression. In order to do that, you need to understand the underlying xml model.

The namespace w; is preserved for the predefined wiki elements.
TODO: check how this will work with interwiki links.

 <w:pages>
   <aPage1>
     <w:author> ... </w:author>
     <w:created> ... </w:created>
     <w:pageName> ... </w:pageName>
     <w:lastModified> ... </w:lastModified>
     <w:versionNumber> ... </w:versionNumber>
     <w:properties>
       <aProperty1> ... </aProperty1>
       <aProperty2> ... </aProperty2>
     </w:properties>
     <w:attachments>
       <anAttachment1>
         <w:fileName> ... </w:fileName>
         <w:fileSize> ... </w:fileSize>
       </anAttachment1>
     </w:attachments>
     <w:versions>
       <v1> ... </v1>
       <v2> ... </v2>
       <v3> ... </v3>
     </w:versions>
     <w:to>
       <aPageX1> ... </aPageX1>
       <aPageX2> ... </aPageX2>
     </w:to>
     <w:from>
       <aPageY1> ... </aPageY1>
       <aPageY2> ... </aPageY2>
     </w:from>
     ... <pagecontent - wiki markup text> ...
   </aPage1>
   <aPage2> ... <aPage2>
 </w:pages>

Shortcut syntax is defined for properties, attachments and versions. Also the root-path /w:pages/ can be dropped. This way, the syntax becomes backwards compatible with the current syntax.

   /w:pages/SandBox/w:properties/versionLabel
                                           => SandBox/@versionLabel

   /w:pages/SandBox/w:attachments/attach.png
                                           => SandBox/attach.png

   /w:pages/SandBox/w:versions/v127/w:properties/versionLabel
                                           => SandBox/v127/@versionLabel

XPATH expression#

XPATH expression allow for a powerful querying of the wiki repository. (See XPath for more details)

Some examples:

Return a list of to-pages having a fruit variable

  [SandBox/w:to[@fruit]]
Return a list of to-pages where the fruit variable equals 'apple'
  [SandBox/w:to[@fruit='apple']]
Use (brackets) when you need logical operators (avoid syntax ambiguity)
  [(SandBox/w:to[@fruit='apple'] | SandBox/w:to[@fruit='approved'])]
XPATH evens supports string functions. Following example returns a list of pages with the search string matched
  [SandBox/w:to[contains(text(),'jsp')]]
  [SandBox/w:from[starts-with('Description')]]

Implementation#

It should be possible to use a standard xpath processing java library as a plugin to wiki to support this kind of expressions. Probably, we need to write some back-end to provide the xpath with a virtual xml structure to mimic the internal repository of JSPWiki.

Ref. JXPATH Apache library. Check it.

Wiki Link Format#

With the extended syntax, a wiki link can now return (i) a hyperlink, (ii) a variable value, (iii) a set of hyperlinks or (iv) a set of values. Therefor additional formatting capabilities are needed.

Standard wiki link format syntax allows a static format text.

  [Play around|Sandbox]
More elaborated format string allows to reference variables inside the referenced page or attachement.
  [Speed is @speed|Sandbox]
  [@filesize|Sanbox/attach.png]
In case the wiki link return multiple results, the format string is iterated over each result. Example: following expression returns a bullet list of pages with the value of @liveVersion and a link to that page as well. use . to refer to the iterated result of the wiki-path
  [* @pagename has version @liveVersion, here is the [link|.] |Sandbox/w:to]
 

Use page variables (prefixed with $) to replace more complex format strings.

  [{SET formatAuthor='Author of @pagename is @author' }]
  [$formatAuthor|Sandbox/w:to]

  [{SET format='* ./$pagename has version ./$liveVersion, here is the [link|.]' }]
  [[{$format}]|wiki-path] 
               idem, with format string defined in $format of this page

  [[SandBox/$format]|wiki-path] 
               idem, with format string defined in $format of the Main page

  || PageName     || LiveVersion   || Link
  [{| ./$pagename | ./$liveVersion | [link|.] }|wiki-path] 
               idem, with table header and table body as output format

Please log your remarks/suggestions here

Yup. Great idea. Would go together excellent with the idea of using JSR-170 as a backend repository...

-- JanneJalkanen


agree, it's a very good idea to use the namespace abbriviation in order to identify xpath queries inlined to the content.

some smaller questions towards a structure free of redundancy:

  • do you mind to specify a property more than once in order to form a set of values under one name?
    • looks like this is consitent to your use of set-returns in your xpath results
  • I wonder how you would keep the tos and froms consistent over a wiki repository
  • I wonder what's the difference between w:to and any other property set - other than it's used more often
  • I would recommend to have one page element for each page version, as you did. I wonder why you need all the versions specified in one page, though.
  • As a result here's Rolfs slightly improved version

--rsc, 24-May-2006


Great idea. However I see as a drawback in terms of usageal that it would add yet one new way to build content or lists out of other WIki pages. As far as I know, we have:

  • Tasks Plugin, although the name is misleading, is an elaborate query engine to build tables out of several source pages.
    • Pros: outputs contents of source poages (not only links to source pages), filters using arbitrary criteria on the contents itself
    • cons: non-standard plugin, and slightly constrains the source pages structure, constrains the result format (table).
  • Query Plugin, again misnamed, builds a list of links references, based on references only (TOs and FROMs). This is somehow an elaborate form of the Referring Pages Plugin, which lists only the FROMs).
    • Pros: performance (supposedly), as it queries the ReferenceManager, and does not have to traverse page contents.
    • Cons: non-standard plugin, outputs only links (no content), forces link structure on source pages, no content filtering
  • IdeaWikiLinksThroughXPATHIncludingSubPagesSupport, the mechanism suggested on this very page.
    • Pros: configurable formatting, filter criteria based on links and metadata contents (variables, attachments, versions), may end up into JSPWiki core as Janne seems interested :o)
    • Cons: no filtering on raw text contents (other than variables or attachments), but maybe I misunderstood your examples, no filtering on page names (as of the examples, although it can surely be included for cheap)

Overall, merging the 3 ideas within a single mechanism, preferrably included in JSPWiki core, would make up a powerful Wiki query engine, enabling usage of Wiki as a database.

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« This particular version was published on 24-May-2006 11:13 by Jerome Duprez.