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

This idea started as an XPATH extension of the page link syntax of JSPWiki.

It has been extended with new ideas of page organising concepts.

Introduction : extend Wiki Link syntax 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[1].

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:pages/SomeSubPage]          =>yield link to a subpage
   [SandBox/w:versions/w:v123]            =>yield link to wiki page version
   [SandBox/w:versions/w:v123/attach.jpg] =>yield link to attachment
or with a more compact convenience syntax :
   [SandBox/@variableX]                   =>yield value of wiki variable
   [SandBox/SomeSubPage]                  =>yield link to the subpage
   [SandBox/w: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:pages]                      =>yield links to all subpages of SandBox
   [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

Organisational Concepts #

The extended [page link] syntax would also provide support to some further extensions of JSPWiki for more advanced organisational concepts such as WikiFarms, WikiWebs, WikiSubPages, WikiCategories and WikiTags. See also ref.[2]

WikiFarm#

URL Syntax: http://baseURL/...

A WikiFarm is a grouping of WikiWebs, running on the same wiki engine, behind the same baseURL. It provides for a common administration platform for a set of wikis. All WikiWebs of a WikiFarm share the same user database and authentication policy.

The WikiFarm SiteMap page provides an overview of all its WikiWebs.

  [/w:wikiwebs]       => renders a list of all WikiWebs' homepages in this WikiFarm

A WikiFarm provides overall administrative settings for properties such as:
baseURL, encoding, searchProvider, plugin.*, interWikiRef.* , rss.*, log4j.* authorizer, userdatabase.*, groupManager, aclManager, (new) defaultwikiweb

WikiWeb#

URL Syntax: http://baseURL/wikiwebnamespace:wikipagename

A WikiWeb allows WikiPages to be grouped into separate namespaces.

This is especially useful when organising large chunks of information. It also improves ease of administration.
However, separate namespaces may also decrease usability as users must remember the WikiWeb name prior to the WikiPage name. Preferably, the name of the current WikiWeb should always be visible in the GUI.

The current WikiWeb defines the scope of several wiki functions such as PageIndex, RecentChanges, UnusedPages, UndefinedPages and FindPage. An extra wiki-web option is to be added to the FindPage (and other plugins) to allow searches in other sibling WikiWebs. A WikiWeb may want to provide its own global pages such as LeftMenu, LeftMenuFooter, CopyrightNotice, EditPageHelp, etc.. [3]

A WikiWeb may specify a dedicated location of its page repository and have a dedicated security policy.

A WikiWeb provides administrative settings via a GUI for properties such as:
frontPage homePage, templateDir, translatorReader.*, pageProvider, attachmentProvider, diffProvider, (new) wikiWebNamespace, wikiWebSkin, wikiWebSecurityPolicy

Possibly, these properties could take another prefix iso jspwiki.

  jspwiki.pageProvider=...   => default pageProvider
  zoo.pageProvider=...       => pageProvider for the 'zoo' WikiWeb 

Example

  [zoo:]              => links to the home page of zoo:
  [zoo:Main]          => link to the top Main page of zoo:
  [zoo:*//Main]       => links to all Main pages of zoo:
  [Main]              => links to zoo:Main when zoo: is the current wiki-web
Q. Is the term WikiWeb clear enough. Other suggestions: wiki-site, ... ?

WikiSubPages#

URL Syntax: http://baseURL/wikiwebnamespace:wikiparentpage/wikisubpage/wikisubsubpage

WikiPages can act as a container for other WikiSubPages as well as attachments. Containment implies that e.g. renaming or deleting a parent WikiPage also impacts all its child pages and attachments.

WikiSubPages inherit the ACLs of their ancestor pages. Child pages can add (=restrict) ACLs to those of the ancestors but never relax them. (parental control ;-)

Example

  [Birds/Stork]         => child pages use / as delimitter
  [/Zoo/Birds/Stork]    => absolute link 
                           (start with / to denote the root of the current WikiWeb)
See also Greedy Page Links to keep your links short and backward compatibile with the current JSPWiki links.

More organising concepts#

While WikiFarms, WikiWebs and WikiSubPages implement pure hierarchical organising concepts. More rich grouping concepts are possible through WikiCategories and WikiTags.

WikiCategories#

WikiPages can be categorised into one or more WikiCategories. See also WikiCategory

In order to mark a page for inclusion in a special category, just link it to the category page. Category links can not be distinguished from ordinary page links. Typically the categorised pages link back to the category pages via Back To... or More Info... or See also ... links. The category page may contain a textual description of the grouping concept. It may use the [{ReferredPagesPlugin}] to automatically list all categorised pages.

Q. Can a category page categorise pages of multiple WikiWebs ? I would tend to say yes, although the [{ReferredPagesPlugin}] would need some extra param to search for links outside the current WikiWeb.

WikiTags#

WikiPages can be tagged with one or more WikiTags.

In order to mark a page with a tag, you will add some metadata to the page. Typically, GUI support is available for easy page tagging (select a tag from the existing set of tags of the current WikiWeb) and to facilitate page searches based on certains tags.

Example:

  [/w:tags/*]          =>list all tags in this WikiWeb
  [*[@tag='food']]     =>list all pages tagged with 'food'

The concept of greedy page links will keep your page links short and provide backward compatibility with the current style of page-linking.

When resolving a [page-link], the wiki-engine will first try to match any of the children of the current page. When no match is found, the wiki-engine will continue its search from the root of the current WikiWeb. Use XPATH expressions to target more specific sets of pages. [4]

With the greedy page link alghorithm, a single [page-link] can now result in one or more clickable page links. By default, the generated set of links are separated with a space. See Formatting Wiki Links to change this formatting.

Example of the greedy page-link algorithm :

Current Page Wiki markup... Links to...
/Zoo [Food] /Zoo/Birds/flamingo/Food
/Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Summer/Food
/Zoo/Birds [Food] /Zoo/Birds/flamingo/Food
/Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Summer/Food
/Zoo/Birds/Stork [Food] /Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Summer/Food
/Zoo/Birds/Stork/Summer [Food] /Zoo/Birds/Stork/Summer/Food
/Zoo/Birds [Main] /Main (the [Birds] has no Main page children)

Example of XPATH expresssions :

Current Page Wiki markup... Links to...
/Zoo/Birds/Stork [Summer/Food] /Zoo/Birds/Stork/Summer/Food
/Zoo/Birds/Stork [./Food] /Zoo/Birds/Stork/Food
/Zoo/Birds/Stork [.//Food] /Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Summer/Food
/Zoo/Birds/Stork/Summer [../Food] /Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Sumer [..//Food] /Zoo/Birds/Stork/Food
/Zoo/Birds/Stork/Summer/Food
/Zoo/Birds/Stork [../*/Food] /Zoo/Birds/flamingo/Food
/Zoo/Birds/Stork/Food
any page [/Zoo/Birds] /Zoo/Birds
any page [/Zoo/Birds/*/Food] /Zoo/Birds/flamingo/Food
/Zoo/Birds/Stork/Food
Q. What is the default format of a link ? Is it the absolute path, such as /Zoo/Birds/Stork/Summer/Food. Or the relative (and shorter) path, such as Stork/Summer/Food or ./Stork/Summer/Food ?

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.

 <w:pages>
   <aPage1>
     <w:properties>
       <w:name> ... </w:name>
       <w:path> ... </w:path>
       <w:length> ... </w:length>
       <w:author> ... </w:author>
       <w:created> ... </w:created>
       <w:lastModified> ... </w:lastModified>
       <w:versionNumber> ... </w:versionNumber>
       <aProperty1> ... </aProperty1>
       <aProperty2> ... </aProperty2>
     </w:properties>
     <w:attachments>
       <anAttachment1>
         <w:properties>
           <w:name> ... </w:name>
           <w:path> ... </w:path>
           <w:length> ... </w:length>
           <w:author> ... </w:author>
           <w:created> ... </w:created>
           <w:lastModified> ... </w:lastModified>
           <w:versionNumber> ... </w:versionNumber>
         </w:properties>
         <w:versions>
           <w:v1> ... </w:v1>
           <w:v2> ... </w:v2>
           <w:v3> ... </w:v3>
         </w:versions>
       </anAttachment1>
     </w:attachments>
     <w:pages>
       <subPage1> ... </subPage1>
       <subPage2> ... </subPage2>
     </w:pages>
     <w:versions>
       <w:v1> ... </w:v1>
       <w:v2> ... </w:v2>
       <w:v3> ... </w: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>
 <w:wikiwebs>
   <wikiweb1:homePage> ... <wikiweb1:homePage>
   <wikiweb2:homePage> ... <wikiweb2:homePage>
 </w:wikiwebs>

Overview of predefined elements inside the Wiki Metadata XML model#

Child Node Description Type
<w:pages> Set of pages. Used as root element or as a collection of sub-pages page nodes
<w:properties> Set of properties, or metadata of a page or attachment properties
<w:attachments> Set of attachments attachment nodes
<w:versions> Set of page or attachment versions page or attachment nodes
<w:to> Set of pages which are being referred by this page (outgoing links) page nodes
<w:from> set of pages which are referring to this page (incoming links) page nodes
<w:wikiwebs> set of pages referring to the rootpages of all wikiwebs in this wikifarm page nodes
Property Node Description Type
<w:name> Page or Attachment Name, including punctuations String
<w:path> Complete path name, including names of parent pages String
<w:author> Name of the author of a page or attachment String
<w:length> length (number of bytes) of a page or attachment number
<w:created> Creation date of a page or attachment Date and Time
<w:lastModified> Last Modification date of a page of attachment Date and Time
<w:versionNumber> Version number of a page or attachment 1..n

Additional notes to the Wiki Metadata XML Model#

  • Wiki Names
    Page or Attachment nodes use a wiki-name without punctuations or blanks. The <w:name> property contains the full name, including punctuations and blanks.
  • Versions node
    Page or Attachment nodes always refer to their current state. The <w:versions> node contains references to all past and current versions. Each version gets a unique sequence number propery like this: w:v1, w:v2, w:vxx.
  • Same Name Siblings (JSR-170[1], chap 4.3)
    All nodes inside <w:pages>, <w:attachments> or <w:property> must have a unique name. In other words, there can not be a page with the same name inside a single <w:pages> node; all page properties have unique names etc. (multi-value properties need further investigation)
  • Virtual nodes
    The <w:from> and <w:to> nodes are virtual in the sense that they are computed on request, rather then being physically present in the document tree.

Wiki Link Compact Syntax#

A compact convenience syntax is defined for properties, subpages, 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:pages/SomeSubPage/w:properties/someMetaData
                                           => SandBox/SomeSubPage/@someMetaData

   /w:pages/SandBox/w:versions/w:v127/w:properties/versionLabel
                                           => SandBox/w: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 even 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')]]
You can use local wiki page variables inside xpath expressions too, prefix them with a $.
  [{SET node='Main' }]

  [$node/w:to]

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.

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]
Use the @-syntax to retrieve the value of page or attachment properties.
  [Speed is @speed|Sandbox]
  [@w:length|Sanbox/attach.png]
Combine property values and links like this (nested brackets):
  [This [.] is ranked at @ranking |Sandbox]

In case the wiki link returns 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.

  [* @w:name has version @liveVersion, here is the [link|.] |Sandbox/w:to]

You can use other page variables to replace more complex format strings.

  [{SET format='* @w:name has version @liveVersion, here is the [link|.]' }]
  [${format} |wiki-path] 
you can do the same with a format string from another page:
  [[SandBox/@format]|wiki-path] 
Here is an example which returns a tabular format. By putting the format string in a separate variable, you avoid the need to escape the vertical bar ( | ) which has a separate meaning inside a wiki link. Obviously, you could also use the tilde ( ) to escape the bars.
  [{SET tableformat='| @w:name | @liveVersion | [link|.]' }]
  || PageName     || LiveVersion   || Link
  [ ${tableformat} | wiki-path] 

Footnotes#

[#1] JSR-170 : see http://www.jcp.org/en/jsr/detail?id=170

[#2] Inspired by lots of stuff on the jspwiki mailing list, also on http://twiki.org/cgi-bin/view/Codev/OrganizingPrinciples

[#3] WikiWebs may define they own global pages suchs as [LeftMenu] etc. By default, a WikiWeb will inherit these pages from the default WikiWeb at creation.
Example contents of [LeftMenu] of a newly created WikiWeb:

  [{InsertPage page='<default-wiki-web>:LeftMenu'}]

[#4] The greedy page link algoritm actually executes following XPATH expressions:

  • If not-empty, return [.//pagename] : matches all subpages of the current page
  • Otherwise return [//pagename] : matches all subpages of the root page of the current WikiWeb

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

Thx for the improved version -- definitely contains good ideas for improvement. I've updated the body of the doc, adding some stuff I found was missing.
    • I took the assumption that a wiki variable can only appear once on a page, so no multiple occurences
    • the to's and from's are computed at run time, not physically present in the tree
    • all the elements starting with w: are predefined wiki-syntax elements; this allows to differentiate them from user defined metadata
    • the versions grouping allows to retrieve a list of all versions of a page -- such a query would mimic the page-info section of jspwiki
--DF

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 database.

-- JDuprez

Indeed, that is exactly the idea: Trying to define a not too complex syntax, so we can replace the need of several query-kind-of-plugins. However, I think xpath may still not be powerful enough ;-) BTW, I would also categorize InsertVersionPlugin under overlapping plugins with this syntax. Maybe there are even more... --DF

May be we could structure the effort in tasks:#

  1. define invariant Metadata, to be input/edited by the user
    1. define page properties where a property name is chosen by the user
    2. there are an evolving set of static core properties a user might choose and assign values to, like subpage
      1. core properties will be equipped with a defined meaning, implemented e.g. by a plugin
    3. ...
  2. define a set of default dynamic Metadata to every page representing some actual state
    1. page URLs that links to the page
    2. page URLs that ar linked to with the page
    3. available (other) versions to the page
    4. ...

this way I understood JDuprez
as DF said: all Metadata should be subject to selection/query, regardless of static or dynamic

I noticed a gap in the definition of subpage:#

  • Is a subpage to a page the same as another one that the page links to? No.
  • Is a subpage a page that exists only in conjunction with its parent? Yes.
  • What about links in circles? Can a page be its own subpage? May be. Doesn't make sense.
  • I see a distinction (see SubPages and links from there)
    • a subpage is text closely related to its parents
    • a subpage could belong to more than one parent (no embedding, no file system directory, but a static link, separate implementation from concept, any page provider should do)
    • a subpage will be deleted in case all its parents are deleted (UML: composition)
    • you can search thru subpages, omit all loosly linked pages (this is the point)
    • a page may be shown tabbed together with its first level subpages
    • you may have a plugin offering navigation thru the tree of subpages

xpath has several advantages we should not overlook#

  • it's more fashionable than SQL
  • it's more well thought than an own-build can ever be
  • I cannot see a limit
    • the only thing you got to solve is insert dynamic Metadata somewhere in the pages properties at runtime
      seems not to be a hard thing to do

To name some
A disadvantage I'm aware of: xpath might not be easy to learn, but that's a question of a good tutorial as easy questions are easy to construct, even in xpath.

single property values are the same concept as mulitple ones#

if you agree to the convention that the first is returned in case only a single is requested

However, multiple values for properties -- or the same property name more than once (this just syntax) -- are able to cover the concept of subpages, too.

--Rolf Schumacher, 25-May-2006

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« This page (revision-58) was last changed on 03-Mar-2011 11:02 by Janne Jalkanen