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RELAX Quick Reference
By J. David Eisenberg
October 16, 2000

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.

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