xml/relaxng/src/META-INF/relaxng-plugin.xml

<idea-plugin>
  <extensions defaultExtensionNs="com.intellij">
    <errorHandler implementation="com.intellij.diagnostic.ITNReporter" />
    <gotoSymbolContributor implementation="org.intellij.plugins.relaxNG.GotoSymbolContributor" />
    <xml.schemaProvider implementation="org.intellij.plugins.relaxNG.config.NoNamespaceSchemaProvider" />
    <hectorComponentProvider implementation="org.intellij.plugins.relaxNG.config.NoNamespaceConfigImpl$HectorProvider" />

    <fileTypeFactory implementation="org.intellij.plugins.relaxNG.compact.RncFileType$Factory" />
    <completionData fileType="RNG Compact" className="org.intellij.plugins.relaxNG.compact.RncCompletionData" />
    <standardResourceProvider implementation="org.intellij.plugins.relaxNG.ApplicationLoader$ResourceProvider" />

    <annotator language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.ReferenceAnnotator" />
    <annotator language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.model.annotation.ModelAnnotator" />
    <externalAnnotator language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.validation.RngSchemaValidator" />

    <lang.parserDefinition language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RncParserDefinition" />
    <lang.braceMatcher language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RngCompactLanguage$MyPairedBraceMatcher" />
    <lang.commenter language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RngCompactLanguage$MyCommenter" />
    <lang.foldingBuilder language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.folding.RncFoldingBuilder" />
    <lang.formatter language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.formatting.RncFormattingModelBuilder" />
    <lang.namesValidator language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RngCompactLanguage$MyNamesValidator" />
    <lang.syntaxHighlighterFactory key="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RngCompactLanguage$MySyntaxHighlighterFactory" />

    <lang.elementManipulator forClass="org.intellij.plugins.relaxNG.compact.psi.RncFileReference" implementationClass="org.intellij.plugins.relaxNG.RncFileReferenceManipulator" />

    <lang.documentationProvider language="RELAX-NG" implementationClass="org.intellij.plugins.relaxNG.compact.RngCompactLanguage$MyDocumentationProvider" />

    <fileBasedIndex implementation="org.intellij.plugins.relaxNG.model.resolve.RelaxSymbolIndex" />
    <include.provider implementation="org.intellij.plugins.relaxNG.model.resolve.RelaxIncludeProvider"/>

    <externalAnnotator language="XML" implementationClass="org.intellij.plugins.relaxNG.validation.RngSchemaValidator" />
    <lang.documentationProvider language="XML" implementationClass="org.intellij.plugins.relaxNG.RngDocumentationProvider" />
    <psi.referenceContributor implementation="org.intellij.plugins.relaxNG.RelaxNGReferenceContributor"/>

    <dom.fileDescription implementation="org.intellij.plugins.relaxNG.RngDomFileDescription$RngChoiceDescription"/>
    <dom.fileDescription implementation="org.intellij.plugins.relaxNG.RngDomFileDescription$RngElementDescription"/>
    <dom.fileDescription implementation="org.intellij.plugins.relaxNG.RngDomFileDescription$RngGrammarDescription"/>
    <dom.fileDescription implementation="org.intellij.plugins.relaxNG.RngDomFileDescription$RngGroupDescription"/>
    <dom.fileDescription implementation="org.intellij.plugins.relaxNG.RngDomFileDescription$RngInterleaveDescription"/>

    <dom.implementation interfaceClass="org.intellij.plugins.relaxNG.xml.dom.RngDefine" implementationClass="org.intellij.plugins.relaxNG.xml.dom.impl.RngDefineImpl"/>
    <dom.implementation interfaceClass="org.intellij.plugins.relaxNG.xml.dom.RngGrammar" implementationClass="org.intellij.plugins.relaxNG.xml.dom.impl.RngGrammarImpl"/>
    <dom.implementation interfaceClass="org.intellij.plugins.relaxNG.xml.dom.RngInclude" implementationClass="org.intellij.plugins.relaxNG.xml.dom.impl.RngIncludeImpl"/>
    <dom.implementation interfaceClass="org.intellij.plugins.relaxNG.xml.dom.RngRef" implementationClass="org.intellij.plugins.relaxNG.xml.dom.impl.RngRefImpl"/>
    <xml.html5SchemaProvider implementation="org.intellij.plugins.relaxNG.xml.RngHtml5SchemaProvider"/>
    <metaDataContributor implementation="org.intellij.html.RngHtml5MetaDataContributor"/>

    <localInspection shortName="UnresolvedReference" displayName="Unresolved References" groupName="RELAX NG" enabledByDefault="true"
                     level="ERROR" implementationClass="org.intellij.plugins.relaxNG.inspections.RngDomInspection"/>
    <localInspection shortName="UnusedDefine" displayName="Unused Define" groupName="RELAX NG" enabledByDefault="false" level="WARNING"
                     implementationClass="org.intellij.plugins.relaxNG.inspections.UnusedDefineInspection"/>

  </extensions>

  <project-components>
    <component>
      <interface-class>org.intellij.plugins.relaxNG.config.NoNamespaceConfig</interface-class>
      <implementation-class>org.intellij.plugins.relaxNG.config.NoNamespaceConfigImpl</implementation-class>
    </component>
  </project-components>

  <application-components>
    <component>
      <implementation-class>org.intellij.plugins.relaxNG.ApplicationLoader</implementation-class>
    </component>
  </application-components>

  <actions>
    <action id="ConvertSchemaAction" class="org.intellij.plugins.relaxNG.convert.ConvertSchemaAction"
            text="Convert Schema..."
            description="Converts the selected Schema document (RNG, RNC, XSD, DTD) into another format">
      <add-to-group group-id="ToolsXmlGroup" anchor="after" relative-to-action="GenerateDTD" />
    </action>
  </actions>
</idea-plugin>