Background

• XForms for patient record data collection @ Cleveland Clinic Foundation
• Thin (expressive) client deployment
• Declarative vocabulary for describing user interfaces (UI)
• Generate XHTML / XForms live via XSLT
• Terminology-driven generation of XHTML / XForms
  • RDF vocabulary describes a domain
  • User interface vocabulary references terms in a domain
  • Majority of leaf terms are rendered as controlled vocabularies
  • The generation queries domain description for relevant constraints
• Less than 1% of generated user interfaces is Javascript
  • Very minimal scripting

The XForm paradigm

• Rich Web Application Backplane
  • A powerful architectural style for remote manipulation of XML
  • Emphasizes reusable components for both scripting and declarative programming models
  • 
• Highly declarative MVC architecture
• Browser agnosia
• A core instruction set for UI programming

XForms challenges

• Authoring
  • Very recursive structure
  • Verbosity
  • Significant learning curve
• Limited programmatic expressiveness (compared to XSLT / Javascript)
  • Somewhat addressed by XForms 1.1 Working Draft
• Implementation-independent control styling

The XSLT proposition

• Powerful mechanism for enabling declarative problem solving
• "Modality segregation"
• 
• Separation of content from:
  • Presentation (XHTML,PDF,..) - 1
  • Authoritative semantics (GRDDL, RDFS, & OWL) - 2
• Separation of presentation from application logic? - 3

The scenario: editing Atom

• Very recursive XML format
  • Lends itseslf well to a declarative approach
• Rather popular format
  • Lots of data to test with
• Atom Publishing Protocl (APP) requires an expressive submission mechanism

An experiment with XUL / XSLT / XForms

• The Value proposition?
  • Further abstraction of application logic
  • Ease of authoring

Mapping XUL widgets to XForms / XHTML

• Lower-level widgets written using XUL
• XSLT stylesheet includes templates for transforming XUL to XHTML and XForms
• XUL Mapping
  • xul:grid -> table
  • xul:groupbox -> fieldset
  • xul:label -> xforms:output
  • xul:textbox -> xforms:input | xforms:secret | xforms:textarea
  • xul:radiogroup -> xforms:select1
  • xul:listbox/xul:listitem -> xforms:select1
  • xul:menulist/xul:menupopup/xul:menuitem -> xforms:select1
  • xul:groupbox -> fieldset
  • xul:tabbox -> xforms:switch

A high-level abstraction for UI patterns

• ui:existential-block
  • A widget which renders a (labeled) placeholder when absent

  • <xsl:template match="ui:existential-block">        
        <xf:group ref="current()[not({@node})]">
            <img src=".. add icon .." alt="Click to add {@node}"/>
        </xf:group>
        <xsl:apply-templates select="*"/>
    </xsl:template>                      
                        

• ui:attribute-anchor
  • A simple widget for an element with multiple attributes
    • used for atom:link and atom:category

  • <xsl:template match="ui:attribute-anchor">
        <xf:group ref="{@node}">
            <xsl:for-each select="ui:attribute">
                <xf:input ref="{@attrName}">
                    <xf:label><xsl:value-of select="@label"/></xf:label>
                </xf:input>                
            </xsl:for-each>
        </xf:group>
    </xsl:template>                        
                        

<ui:existential-block node="atom:category">
    <xf:repeat nodeset="atom:category">
        <ui:attribute-anchor node=".">
            <ui:attribute label="Scheme" attrName="@scheme"/>
            <ui:attribute label="Term"      attrName="@term"/>
        </ui:attribute-anchor>
    </xf:repeat>               
</ui:existential-block>        
    

<ui:existential-block node="atom:link">
    <xf:repeat nodeset="atom:link">
        <ui:attribute-anchor node=".">
            <ui:attribute label="Relation" attrName="@rel"/>
            <ui:attribute label="URL"      attrName="@href"/>
        </ui:attribute-anchor>
    </xf:repeat>                       
</ui:existential-block>        
    

Processing mixed vocabularies

• How is this mix of heavily recursive vocabularies transformed?
• Push processing
• Powerful mechanism for processing declarative markup

Other considerations

• Multiplexing XForms output
  • Accommodating XForms implementation quirks (FormsPlayer, Mozilla, ..)
• Merging XUL & XForms behavior
  • Event processing
  • XPath binding