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Relax NG

This illustrates the basic features of RelaxNG.
<?xml version="1.0"?>
<zoo>
<animal id="l123444" id2="L234423">
<name>Mighty</name>
<type>lion</type>
<kg>135</kg>
<imported/>
</animal>
<animal id="b355345">
<name>Lucky</name>
<type>bear</type>
<kg>205</kg>
</animal>
</zoo>
<?xml version="1.0"?>
<element name="zoo"
xmlns="http://relaxng.org/ns/structure/1.0">
<zeroOrMore>
<element name="animal">
<attribute name="id"/>
<element name="name"><text/></element>
<element name="type"><text/></element>
<element name="kg"><text/></element>
<optional>
<element name="imported"><empty/></element>
<attribute name="id2"/>
</optional>
</element>
</zeroOrMore>
</element>
oneOrMore can be used in place zeroOrMore, if at least one child element must be present.
RelaxNG does not allow element to be empty. So the following is invalid: <element name=”x”/>
The order of elements is significant, but the order of the attributes is not.

This illustrates the use of choice, group, and data.
<?xml version="1.0"?>
<personalDetails>
<person>
<name>Ali</name>
<sex>m</sex>
</person>
<person sex="f">
<firstName>Sharon</firstName>
<lastName>Ann</lastName>
</person>
</personalDetails>
<?xml version="1.0"?>
<element name="personalDetails"
xmlns="http://relaxng.org/ns/structure/1.0">
<zeroOrMore>
<element name="person">
<choice>
<element name="name"><text/></element>
<group>
<element name="firstName"><text/></element>
<element name="lastName"><text/></element>
</group>
</choice>
<choice>
<element name="sex">
<data type="string" datatypeLibrary=
"http://www.w3.org/2001/XMLSchema-datatypes">
<param name="maxLength">1</param>       
</data>
</element>
<attribute name="sex">
<choice>
<value>m</value>
<value>f</value>
</choice>
</attribute>
</choice>
</element>
</zeroOrMore>
</element>
The attribute datatypeLibrary can appear in any ancestor element instead.

This illustrates the use of list, interleave, and mixed.
<?xml version="1.0"?>
<data>
<myList1>SN 4432 1234 3287 ZZ</myList1>
<myList2><b/><c/><a/></myList2>
<myList3>as324<a/>23423<b/>4sd</myList3>
</data>
<?xml version="1.0"?>
<element
name="data"  
xmlns="http://relaxng.org/ns/structure/1.0"
datatypeLibrary=
"http://www.w3.org/2001/XMLSchema-datatypes">
<element name="myList1">
<list>
<data type="string"/>
<oneOrMore>
<data type="int"/>
</oneOrMore>
<optional>
<data type="string"/>
</optional>
</list>
</element>
<element name="myList2">
<interleave>
<element name="a"><empty/></element>
<element name="b"><empty/></element>
<optional>
<element name="c"><empty/></element>
</optional>
</interleave>
</element>
<element name="myList3">
<mixed>
<element name="a"><empty/></element>
<element name="b"><empty/></element>
</mixed>
</element>
</element>
Combining attributes with interleave has the same effect as combining them with group.

This is a rather complex example that demonstrates the various ways to use references.
<?xml version="1.0"?>
<!-- badminton.xml --> <badminton id="3432">
<players.min>2</players.min>
<players.max>4</players.max>
</badminton>
<?xml version="1.0"?>
<!-- badminton1.rng --> <element
name="badminton"
xmlns="http://relaxng.org/ns/structure/1.0">    <externalRef href="badminton2.rng"/>
</element>
<?xml version="1.0"?>
<!-- badminton2.rng --> <grammar xmlns="http://relaxng.org/ns/structure/1.0">
<include href="badminton3.rng">
<define name="idd">
<attribute name="id"/>
</define>
</include>
<define name="pNum" combine="interleave">
<element name="players.min">
<text/>
</element>
<ref name="idd"/>
</define>
<start>
<ref name="pNum"/>
</start>
</grammar>
<?xml version="1.0"?>
<!-- badminton3.rng --> <grammar xmlns="http://relaxng.org/ns/structure/1.0">
<define name="pNum">
<element name="players.max">
<text/>
</element>
</define>
<define name="idd">
<element name="id">
<text/>
</element>
</define>
</grammar>
Theoretically, the three schema files could be merged into one. They appear as separate files to illustrate externalRef and include here. The include element, if not empty, contains definitions that override the included definitions.
The ‘combine’ attribute can take other values such as choice.
In a grammar definition, there can be recursive references within an element.
If a nested grammar is used, parentRef can be used in place of ref to escape out of the current grammar and reference a definition from the parent.
<notAllowed/> never matches anything. It can be used with combine=”choice” to allow the including pattern to specify additional choices.

You can declare a namespace for an element or an attribute with the attribute ‘ns’.
<?xml version="1.0"?>
<xn1:section id="199"
xmlns:xn1="http://example1.com"
xmlns:xn2="http://example2.com">
<xn1:subsection1/>
<xn2:subsection2/>
</xn1:section>
<?xml version="1.0"?>
<element name="section"
xmlns="http://relaxng.org/ns/structure/1.0"
xmlns:myNS="http://example2.com"
ns="http://example1.com">
<element name="subsection1"><empty/></element>
<element name="myNS:subsection2"><empty/></element>
<attribute name="id"/>
</element>
Note that element inherits the value of the ‘ns’ attribute of the nearest ancestor, but attribute does not. The XML document will be invalid if xn1:id=”199” is used instead, because the id attribute is declared to have the empty (or absent) namespace.
Here
<element name=”myNS:subsection2”>
is equivalent to:
<element name=”subsection2” ns=”http://example2.com”>

This allows an element to have any attribute with a qualified name, but if there was an ‘xml:space’ attribute, it had the value ‘default’ or ‘preserve’.
<?xml version="1.0"?>
<element
name="example"
xmlns="http://relaxng.org/ns/structure/1.0">
<zeroOrMore>
<attribute>
<anyName>
<except>
<name>xml:space</name>
</except>
</anyName>
</attribute>
</zeroOrMore>
<optional>
<attribute name="xml:space">
<choice>
<value>default</value>
<value>preserve</value>
</choice>
</attribute>
</optional>
</element>
Instead of name, you can use nsName to contain any name with the namespace URI specified by the ‘ns’ attribute. Eg.: <element>
<anyName>
<except>
<nsName/>
<nsName ns=""/>
</except>
</anyName>
</element> will contain any namespace-qualified element provided it is qualified with namespace other than that of parent element.

(Courtesy of http://relaxng.org/tutorial-20011203.html#IDAFLZR)

You can attach annotations anywhere. div allows an annotation to be applied to a group of definitions in a grammar.
<?xml version="1.0"?>
<grammar xmlns:m="http://www.example.com/module">
<m:documentation>Here are the animals.
</m:documentation>
<div m:name="These are reptiles.">
<define name="crocodile">
<attribute name="crocodile"/></define>
<define name="snake">
<attribute name="snake"/></define>
<define name="alligator">
<attribute name="alligator"/></define>
</div>
<div m:name="These are mammals.">
<define name="dog">
<attribute name="dog"/></define>
<define name="cat">
<attribute name="cat"/></define>
<define name="tiger">
<attribute name="tiger"/></define>
</div>
</grammar>