XML Prague 2010

Introduction of the AXEL Javascript library for XML authoring in the browser
- S. Sire, C. Vanoirbeek, V. Quint, C. Roisin, Authoring XML all the Time, Everywhere and by Everyone. In Proceedings of XML Prague 2010, pages 125-149, Institute for Theoretical Computer Science, March 2010
Self-service demo:
- click a first time on “edit” to transform the bibliographic reference into an editor
- click on “xml” (resp. “hide”) to show (resp. hide) its current XML content
- click on “preview” to hide / show editor structure editing controls

Motivation: full XML stack

XML web development

Languages (W3C)

XPath => XQuery, XSLT
XForms XTiger XML (Adaptable XML Editing Library)

Native XML databases

eXist-DB, Sausalito, baseX, Marklogic

XRX programming style and 2/3 architectures
But still very few application frameworks !

RESTXQ, EXPath
Orbeon Forms, Oppidum

Oppidum Principles

A unique XML file to represent the application architecture
the mapping associates each REST resource from the application with a rendering pipeline

Oppidum Pipeline

Limited to 3 steps (KISS-principle)
- a model implemented as an XQuery script
- a (optional) view implemented as an XSLT transformation
- an (optional) epilogue implemented as a unique XQuery script called epilogue.xql
sample :

Article Editing Application

Fully specificed by 6 pipelines

Mapping file example

  <collection name="articles">
    <item> => articles/xml-london[.xml]
      <access>
        <rule action="edit POST" role="g:authors" message="author"/>
      </access>
      <model src="oppidum:actions/read.xql"/>
      <view src="article/article2html.xsl"/>
      <action name="edit"> => articles/xml-london/edit
        <model src="actions/edit.xql"/>
        <view src="views/edit.xsl"/>
      </action>
      <action name="POST"> => POST articles/xml-london
        <model src="actions/write.xql"/>
      </action>
      <collection name="images"> => articles/xml-london/images/
        <model src="models/forbidden.xql"/>
        <action name="POST"> => POST articles/xml-london/images/
          <model src="images/upload.xql"/>
        </action>
        <item> => articles/xml-london/images/1.png
          <model src="images/image.xql"/>
        </item>
      </collection>
    </item>
  </collection>

Oppidum Execution Model

a two time engine
eXist-DB implementation
- 1st step : controller.xql calls gen:process( HTTP Request )
- 2nd step: URLRewriteFilter executes pipeline

Oppidum Design Patterns

Templating system

<html xmlns="http://www.w3.org/1999/xhtml"
     xmlns:site="http://oppidoc.com/oppidum/site">
  <body>
    <div id="article">
      <site:content/>
    </div>
  </body>
</html>

Sample flow

Model output

<Document>
  <Parag>Hello World</Parag>
</Document>

View output

<site:view>
  <site:content>
    <p>Hello World</p>
  </site:content>
</site:view>

Epilogue output

<html xmlns="http://www.w3.org/1999/xhtml">
  <body>
    <div id="article">
      <p>Hello World</p>
    </div>
  </body>
</html>

Epilogue templating function

universal typeswitch function (cut-and-paste between projects) to include in the epilogue

declare function local:render( $cmd as element(), $source as element(),
  $view as element()* ) as element()
{
  element { node-name($source) }
  {
    ...typeswitch function calling site:branch function
       for every  site:* extension point...
  }
};

application-dependent function defining the extension points

declare function site:branch( $cmd as element(), $source as element(),
  $view as element()* ) as node()*
{
  typeswitch($source)
  case element(site:skin) return site:skin($cmd, $view)
  case element(site:lang) return site:lang($cmd, $view)
  case element(site:navigation) return site:navigation($cmd, $view)
  case element(site:error) return site:error($cmd, $view)
  case element(site:login) return site:login($cmd)
  ...
  default return $view/*[local-name(.) = local-name($source)]/(*|text())
  (: default treatment to implicitly manage other modules :)
};

More design patterns

Skinning applications
- declarative way to keep the association between CSS and JS files and application pages into a skin.xml resource inside the database
Error and message management (Flash a-la Ruby on Rails)
Data mapping
- maintaining a relation between URL input space hierarchy and database collections hierarchy
Form-based access control
Development life cycle (mode="dev|test|prdo" attribute)

Application : Focus

Newsletter editor
- editorial tool chain for publishing a 4 pages newsletter (3000 printed copies)

Application : Alliance

Web site of the Association Alliance
- form editor for participant registration with tool chain to publish badges and list of participants

Application : UAP

Web site of the Union des Artisans du Patrimoine de Belgique
- moderated classified ads service for the craftmen member of the association

Application : PSE

database of startup companies member of the Science Park at EPFL
- multilingual content and search engine (Apache Lucene)
- generation of personalized recommendations to improve company pages
- JSON export towards an internal advertising TV screen network

Conclusion

Effective and efficient XML full stack
- implicit “model driven” approach with clear division of work for developers
- user generated content with AXEL and AXEL-FORMS (article XML Prague)
- backend development with eXist-DB and Oppidum (article XML London)
Open source (available on Github)
Opened issues to go beyond "Small Data"
- code portability
  - abstraction layer for cross-database execution environments ?
  - see EXPath Webapp framework ? XProc ? RESTXQ ?
- failover and load balancing

Small Data in the large with Oppidum

XML web development with Oppidum and eXist-DB

Acknowledgements

Introduction

Small data applications (samples)

XML Prague 2010

Motivation: full XML stack

XML web development

Oppidum Principles

Oppidum Pipeline

Article Editing Application

Mapping file example

Oppidum Execution Model

Oppidum Design Patterns

Sample flow

Epilogue templating function

More design patterns

Application : Focus

Application : Alliance

Application : UAP

Application : PSE

Conclusion