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RELAX Quick Reference

October 16, 2000

J. David Eisenberg

Download available

For future reference, download the RELAX quick reference guide (.pdf)

Your entire specification must be wrapped in a <module> 


   <module

      moduleVersion="1.2"

      relaxCoreVersion="1.0"

      targetNamespace=""

      xmlns="http://www.xml.gr.jp/xmlns/relaxCore">



      <interface>

         <export label="root-element"/>

      </interface>



   <!-- specifications follow -->



   </module>

In the tables below, items in gray like this are optional. Items in italics like this indicate values that depend upon your particular application.

Specifying Elements

To specify: RELAX

An empty element

Note: all element rules may have a label. If omitted, it has the same value as the role 


<elementRule role="name" label="name2">

   <empty/>

</elementRule>
Element with no sub-elements 

<elementRule role="name" type="datatype"/>

Element with constraints on content 


<elementRule role="name" type="datatype">

   <constraint value="constraint-value"/>

</elementRule>
Example: 

<elementRule role="age" type="integer">

   <minInclusive value="18"/>

   <maxInclusive value="65"/>

</elementRule>
Element with a single sub-element 

<elementRule role="name">

   <ref label="sub-element/>

</elementRule>

Element with sub-elements that must occur in a particular order

The occurs= attribute can have one of the following values:
  *   occurs zero or more times
  +   occurs one or more times
  ?   occurs zero or one times 


<elementRule role="name">

   <sequence occurs="n">

      <ref label="sub-element1" occurs="n"/>

      <ref label="sub-element2" occurs="n"/>

   </sequence>

</elementRule>
Element with sub-elements that may appear in any order 

<elementRule role="name">

   <choice occurs="n">

      <ref label="sub-element1" occurs="n"/>

      <ref label="sub-element2" occurs="n"/>

   </choice>

</elementRule>

Mixed content element (element can contain text that is not within any of the sub-elements)

The <mixed> element may enclose a <sequence> or <choice> as above. 


<elementRule role="name">

   <mixed>

      <ref label="sub-element"/>

   </mixed>

</elementRule>

A content model for re-use by other elements:

Hedge rules may refer to other hedge rules, but may not have mixed content or data types. 


<hedgeRule label="hedge-rule-label">

   <!-- content model as in elementRule -->

</hedgeRule>

Reference to a <hedgeRule>

You may intersperse <ref> and <hedgeRef> as required when defining an element's content. 


<elementRule role="name">

   <hedgeRef label="hedge-rule-label"/>

</elementRule>

Specifying Tags

Each element in a document is associated with tag. The role= in an <elementRule> matches the tag name.

To specify: RELAX

A tag with no attributes

All tags may have a role, which, if omitted, is given the same value as the label 


<tag label="name" role="tag-role"/>

A tag with attributes

You may specify that an attribute is required, or that it has a particular data type, or both. 


<tag label="name">

   <attribute name="attr-name-1"/>

   <attribute name="attr-name-2" required="true"/>

   <attribute name="attr-name-3" type="datatype"/>

   <attribute name="attr-name-4"

      required="true"

      type="datatype"/>

</tag>

Constraint on an attribute 


<tag label="name">

   <attribute name="attr-name" type="datatype">

      <constraint value="constraint-value"/>

   </attribute>

</tag>
Example: 

<tag label="water">

   <attribute name="temp" type="decimal">

      <minInclusive value="0"/>

      <maxInclusive value="100"/>

   </attribute>

</tag>

A set of attributes for re-use by other tags: 


<attPool role="pool-label">

   <!-- list of attributes as in tag-->

</attPool>

Reference to an <attPool>

You may intersperse <ref> and <attribute> as required when defining a tag's attributes. 


<tag label="name">

   <ref role="pool-label"/>

</tag>

Context Sensitivity

To make an element's content model dependent upon the element in which it is nested:

  1. Define two <elementRule> models with the same role but different labels.
  2. Other <elementRule>s may now contain the desired sub-element by referring to the appropriate label.

To make an element's content model dependent upon the value of its tag's attribute:

  1. Define two <elementRule> models with the same label but different roles.
  2. Create <tag>s with identical names. Each of these will refer to the appropriate role defined in step one, and have an <attribute> to differentiate them.