<?xml version="1.0" encoding="UTF-8"?>
<!--
  
  RELAX NG Schema for SPARQL Query Results XML Format
  
  This XML schema is normative.
  $Id: result.xsd,v 1.1 2007/10/17 14:48:47 eric Exp $
  
  
-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" targetNamespace="http://www.w3.org/2007/SPARQL/results#" xmlns:res="http://www.w3.org/2007/SPARQL/results#" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <xs:import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="http://www.w3.org/2001/xml.xsd"/>
  <xs:attributeGroup name="xmlLang">
    <xs:attribute ref="xml:lang" use="required"/>
  </xs:attributeGroup>
  <!--
    Using xsi namespaced terms such as xsi:schemaLocation
    is tricky. as Relax requires them to be given when used.  However,
    WXS has this knowledge built in and validators complain when they
    are explicitly listed without a schemaLocation (which is forbidden by
    the WXS spec)..
  -->
  <xs:element name="sparql">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="res:head"/>
        <xs:choice>
          <xs:element ref="res:results"/>
          <xs:element ref="res:boolean"/>
        </xs:choice>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="head">
    <xs:complexType>
      <xs:sequence>
        <xs:element minOccurs="0" maxOccurs="unbounded" ref="res:variable"/>
        <xs:element minOccurs="0" maxOccurs="unbounded" ref="res:link"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="variable">
    <xs:complexType>
      <xs:attributeGroup ref="res:nameAttr"/>
    </xs:complexType>
  </xs:element>
  <xs:attributeGroup name="nameAttr">
    <xs:attribute name="name" use="required" type="xs:NMTOKEN"/>
  </xs:attributeGroup>
  <xs:attributeGroup name="hrefAttr">
    <xs:attribute name="href" use="required" type="res:URI-reference"/>
  </xs:attributeGroup>
  <xs:element name="link">
    <xs:complexType>
      <xs:attributeGroup ref="res:hrefAttr"/>
    </xs:complexType>
  </xs:element>
  <xs:element name="results">
    <xs:complexType>
      <xs:sequence>
        <xs:element minOccurs="0" maxOccurs="unbounded" ref="res:result"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <!-- ASK -->
  <xs:element name="boolean" type="xs:boolean"/>
  <!-- SELECT solution, single match or row -->
  <xs:element name="result">
    <xs:complexType>
      <xs:sequence>
        <xs:element minOccurs="0" maxOccurs="unbounded" ref="res:binding"/>
      </xs:sequence>
      <xs:attribute name="index" type="xs:positiveInteger"/>
    </xs:complexType>
  </xs:element>
  <!-- SELECT binding in a solution -->
  <xs:element name="binding">
    <xs:complexType>
      <xs:choice>
        <xs:element ref="res:uri"/>
        <xs:element ref="res:bnode"/>
        <xs:element ref="res:literal"/>
      </xs:choice>
      <xs:attributeGroup ref="res:nameAttr"/>
    </xs:complexType>
  </xs:element>
  <xs:element name="uri" type="xs:string"/>
  <xs:element name="bnode" type="xs:string"/>
  <xs:element name="literal">
    <xs:complexType mixed="true">
      <xs:attribute name="datatype" type="res:URI-reference"/>
      <xs:attribute ref="xml:lang"/>
    </xs:complexType>
  </xs:element>
  <xs:attributeGroup name="indexAttr">
    <xs:attribute name="index" use="required" type="xs:positiveInteger"/>
  </xs:attributeGroup>
  <xs:attributeGroup name="datatypeAttr">
    <xs:attribute name="datatype" use="required" type="res:URI-reference"/>
  </xs:attributeGroup>
  <xs:simpleType name="URI-reference">
    <xs:restriction base="xs:anyURI"/>
  </xs:simpleType>
</xs:schema>
