wxr.xsd

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xs:schema PUBLIC "-//WordPress//DTD WXR 1.3//EN" "wxr.dtd">
<xs:schema
		xmlns:xs='http://www.w3.org/2001/XMLSchema'
		xmlns:wxr='&WXR_NamespaceURI;'
		xmlns:wp='&WXR_NamespaceURI;1.2/'
		xmlns:fn='http://www.w3.org/2005/xpath-functions'
		elementFormDefault='qualified'
		targetNamespace='&WXR_NamespaceURI;'
		version='&WXR_Version;'>

	<xs:annotation>
		<xs:documentation>
			This is a proof-of-concept XML Schema 1.1 schema for WordPress Export RSS (WXR) proposed version &WXR_Version;.  		
		</xs:documentation>
		<xs:documentation>
			Author: Paul V. Biron/Sparrow Hawk Computing
			Email: paul@SparrowHawkComputing.com
			Web: http://sparrowhawkcomputing.com
			WordPress: pbiron
			Slack: pbiron
		</xs:documentation>
		<xs:documentation>
			This schema is available at http://github.com/pbiron/wxr/1.3-proposed.  If you find any errors in it
			or have suggestions for improvements, please open an issue there.
		</xs:documentation>
		<xs:documentation>
			This schema is intended to serve primarily as documentation of WXR.
			
			There are 2 primary audiences for this schema: 1) WP Core contributors involved in maintaining
			the export/import code (i.e., to serve as a check for keeping the exporter/importer in sync
			when making modifications); and 2) plugin authors who want to write their own export/import code.
			
			The primary purpose of documentation has informed how I have structured this schema (e.g.,
			the use of the 'rss_item_elements' and 'wxr:post_elements' model groups make generated
			documentation more explanatory).
		</xs:documentation>
		<xs:documentation>
			This schema is NOT intended to be used for run-time validation.  The primary reason for this is
			that the XML parsers that are included in PHP do NOT support XML Schema 1.1 (because they are
			all based on libxml, which only supports XML Schema 1.0) :-)
			
			I could write an XML Schema 1.0 schema if folks want to do run-time validation, but I don't think
			it would be worth doing so: 1) the importer doesn't really need it; and 2) the expressivity of
			XML Schema 1.0 is not rich enough to write a very accurate schema for WXR (e.g., the schema
			would have to too tight in some respects and too 'loose' in others, and would report instances
			as valid even they weren't).
			
			For that matter, even this XML Schema 1.1 schema is a little 'loose' in some respects.
		</xs:documentation>
		<xs:documentation>
			As I dug deeper into the Core export/import code (starting with my patch for
			https://core.trac.wordpress.org/ticket/27896 and continuing in my attempts to make
			https://github.com/humanmade/WordPress-Importer be namespace-aware) I've started to come up with
			a list of changes that I think should be made to WXR.  Some of those are documented in
			@todo's throughout this schema (search for 'trac ticket').  Others are documented at
			https://github.com/pbiron/wxr/issues?q=is%3Aissue+label%3A%22core+trac+ticket%22 and
			https://github.com/pbiron/wxr/issues?q=is%3Aissue+label%3A%22meta+trac+ticket%22
		</xs:documentation>
		<xs:documentation>
			In addition to the change in namespace URI, the proposed version of WXR represented by this
			schema also makes a number of changes to WXR element names from what they were in past versions.
			Some of the most prominent changes are: 1) <wp:tag/> and <wp:category/> both use <wxr:term/>;
			2) <wp:author/> has been changed to <wxr:user/>; and 3) <wp:post_id/> has been changed to <wxr:id/>.

			At first blush these changes might seem to be breaking backwards compatibility, which would
			be a bad thing.  However, there is a simple transform from WXR 1.0, 1.1 and 1.2
			to this proposed WXR version.  This transform can be hooked into 'wp_handle_upload' by the
			importer, so that the importer only has to deal with this proposed version of WXR.
			
			I've written 5 different versions of that transform: 1) "simple" XSLT 1.0; 2) XSLT 1.0;
			3) XSLT 2.0; 3) XSLT 3.0; and 4) a PHP class.  The XSLT transforms are much easier to understand
			and maintain (XSLT being a declaritive programming language that is specifically designed to
			transform XML), and the XSLT 3.0 transform is the "preferred" transform because compliant
			XSLT 3.0 processors can use it in streaming manner, i.e., they do not have to load the
			entire WXR instance into a DOM object before transforming it.
			
			Unfortunately, a standard PHP install only includes an XSLT 1.0 compliant XSLT processor :-(
			Hence, the PHP class I wrote.
			
			These tranforms are available at http://github.com/pbiron/wxr/1.3-proposed/xslt.
		</xs:documentation>
		<xs:documentation>
			@todo further study the RSS Board's best practices (@link http://www.rssboard.org/rss-profile) and TRY to
			conform to it...and document the differences, including WHY a recommendation is not followed.
		</xs:documentation>
	</xs:annotation>

	<xs:import schemaLocation='rss-20.xsd'>
		<xs:annotation>
			<xs:documentation>
				This import of the RSS schema document is not technically necessary.  However, it makes generating
				documentation from this schema document easier. 
			</xs:documentation>
		</xs:annotation>		
	</xs:import>

	<xs:simpleType name='email'>
		<xs:restriction base='xs:string'>
			<xs:annotation>
				<xs:documentation>
					@todo check whether WP does any kind of sanitation on email addresses, and if
					so, define this as a non-trivial restriction of xs:string with
					a regex pattern that matches the range of that sanitiation function. 
				</xs:documentation>
			</xs:annotation>
		</xs:restriction>
	</xs:simpleType>

	<xs:simpleType name='date_time'>
		<xs:annotation>
			<xs:documentation>
				Represents the lexical space of the date/time 'fields' of a WP_Post.
			</xs:documentation>
			<xs:documentation>
				@todo consider doing this as a trivial restriction of xs:string, because
				it might not be worth the trouble of maintaining the regex in the <xs:pattern />.
			</xs:documentation>
		</xs:annotation>
		<xs:union>
			<xs:simpleType>
				<xs:annotation>
					<xs:documentation>
						@todo I borrowed this regex from https://stackoverflow.com/a/15967451/7751811.
						While I've tested this with several exports from multiple WP sites and
						it appears to be correct, I haven't done a detailed analysis of the regex
						to prove it to myself that it is actually correct.
					</xs:documentation>
					<xs:documentation>
						Actually, upon further testing it regex was wrong: it had incorrect
						months which can have 31 vs only 30 days.  I have corrected that.
					</xs:documentation>
				</xs:annotation>
				<xs:restriction base='xs:string'>
					<xs:pattern value='((((19|20)([2468][048]|[13579][26]|0[48])|2000)-02-29|((19|20)[0-9]{2}-(0[13578]|1[02])-(0[1-9]|[12][0-9]|3[01])|(19|20)[0-9]{2}-(0[2469]|11)-(0[1-9]|[12][0-9]|30)|(19|20)[0-9]{2}-02-(0[1-9]|1[0-9]|2[0-8])))\s([01][0-9]|2[0-3]):([012345][0-9]):([012345][0-9]))' />
				</xs:restriction>
			</xs:simpleType>
			<xs:simpleType>
				<xs:restriction base='xs:string'>
					<xs:enumeration value='0000-00-00 00:00:00'>
						<xs:annotation>
							<xs:documentation>
								@todo I'm not sure why, but I've seen exports that have this value for one
								or another of the date/time fields.
							</xs:documentation>
						</xs:annotation>
					</xs:enumeration>
				</xs:restriction>
			</xs:simpleType>
		</xs:union>
	</xs:simpleType>
	
	<xs:simpleType name='boolean_as_int_string'>
		<xs:annotation>
			<xs:documentation>
				Represents a boolean value as a string ('0' for false, '1' for true). 
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base='xs:boolean'>
			<xs:pattern value='0|1' />
		</xs:restriction>
	</xs:simpleType>
	
	<xs:simpleType name='comment_ping_status'>
		<xs:annotation>
			<xs:documentation>
				Represents the (comment|ping)_status of a post.
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base='xs:string'>
			<xs:annotation>
				<xs:documentation>
					@todo check whether this enumerated lexical space covers all possible values,
					i.e., this may be too restrictive as it might be possible for plugins
					to use some other status.
				</xs:documentation>
				<xs:documentation>
					@todo I've seen exports where <wxr:comment_status/> and <wxr:comment_status/>
					were 'close' and other times they were 'closed' (within the same WXR document).
					I would think it should be limited to one or the other of those values but not both. 
				</xs:documentation>
			</xs:annotation>
			<xs:enumeration value='open' />
			<xs:enumeration value='closed' />
			<xs:enumeration value='close' />
		</xs:restriction>
	</xs:simpleType>				
	
	<xs:simpleType name='key'>
		<xs:annotation>
			<xs:documentation>
				Represents the lexical space of a WP 'key'.
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base='xs:string'>
			<xs:annotation>
				<xs:documentation>
					@todo define this as a non-trivial restriction of xs:string whose lexical space is the
					range of sanitize_key(), once I have time to figure out what that range is.
				</xs:documentation>
			</xs:annotation>
		</xs:restriction>
	</xs:simpleType>
	
	<xs:simpleType name='post_type'>
		<xs:annotation>
			<xs:documentation>
				Represents the lexical space of a post_type name.
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base='wxr:key'>
			<xs:maxLength value='20' />
		</xs:restriction>
	</xs:simpleType>

	<xs:attribute name='version' type='xs:decimal'>
		<xs:annotation>
			<xs:documentation>
				Represents the version of WXR used in the instance.
			</xs:documentation>
			<xs:documentation>
				Note: a fixed value is not specified for this attribute to enable forwards-compatible
				processing (i.e., future versions of WXR).
			</xs:documentation>
		</xs:annotation>
	</xs:attribute>
	
	<xs:attribute name='slug' type='wxr:key'>
		<xs:annotation>
			<xs:documentation>
				Represents the slug of a WP_Term that is associated with a WP_Post.
			</xs:documentation>
			<xs:documentation>
				This is a replacement for category/@nicename, which is not compliant with the RSS
				spec, since attributes on standard RSS elements that are not defined in the RSS spec
				MUST be in a non-empty namespace.
			</xs:documentation>
		</xs:annotation>
	</xs:attribute>

	<xs:attribute name='wp_version' type='xs:string'>
		<xs:annotation>
			<xs:documentation>
				Represents the version of WP that generated the WXR export.
			</xs:documentation>
		</xs:annotation>
	</xs:attribute>

	<xs:group name='channel_elements'>
		<xs:annotation>
			<xs:documentation>
				This model group consists of the WXR elements that are output at the rss/channel level.  
			</xs:documentation>
		</xs:annotation>
		<xs:all>
			<xs:element name='site_url' type='xs:anyURI' minOccurs='0'>
				<xs:annotation>
					<xs:documentation>
						Represents the URL of the site for which a WXR file is an export.
						
						In a non-multisite setup, element will either be absent or have the
						same value as /rss/channel/link.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='user' minOccurs='0' maxOccurs='unbounded'>
				<xs:annotation>
					<xs:documentation>
						Represents an single WP_User.
					</xs:documentation>
					<xs:documentation>
						@todo open a trac ticket to consider changing the
						<wp:author/> element in WXR 1.0, 1.1 and 1.2 to <wxr:user/>.  While
						the standard exporter (as of WP 4.8) only outputs users who are also
						authors of the posts it exports, my	proposed rewrite of the exporter
						provides hooks that allow plugins to export users independent of
						whether they are the authors of any posts in the export.
					</xs:documentation>
				</xs:annotation>
				<xs:complexType>
					<xs:complexContent>
						<xs:extension base='wxr:open_content'>
							<xs:all>
								<xs:element name='id' type='xs:positiveInteger'>
									<xs:annotation>
										<xs:documentation>
											Represents the ID of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='login' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the user_login of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='email' type='wxr:email'>
									<xs:annotation>
										<xs:documentation>
											Represents the user_email of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='display_name' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the display_name of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='first_name' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the value of the usermeta with whose meta_key is 'first_name' of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='last_name' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the value of the usermeta with whose meta_key is 'last_name' of the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='meta' type='wxr:meta' minOccurs='0' maxOccurs='unbounded'>
									<xs:annotation>
										<xs:documentation>
											Represents a single usermeta associated with the WP_User.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
							</xs:all>
						</xs:extension>
					</xs:complexContent>
				</xs:complexType>
			</xs:element>
			<xs:element name='term' minOccurs='0' maxOccurs='unbounded'>
				<xs:annotation>
					<xs:documentation>
						Represents a single WP_Term.
					</xs:documentation>
				</xs:annotation>
				<xs:complexType>
					<xs:complexContent>
						<xs:extension base='wxr:open_content'>
							<xs:all>
								<xs:element name='id' type='xs:positiveInteger'>
									<xs:annotation>
										<xs:documentation>
											Represents the term_id of the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='taxonomy' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the term_taxonomy of the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='slug' type='wxr:key'>
									<xs:annotation>
										<xs:documentation>
											Represents the slug of the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='parent' type='wxr:key' minOccurs='0'>
									<xs:annotation>
										<xs:documentation>
											Represents the slug of parent of the WP_Term.
										</xs:documentation>
										<xs:documentation>
											Will be absent if the term has no parent.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='name' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the name of the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='description' type='xs:string' minOccurs='0'>
									<xs:annotation>
										<xs:documentation>
											Represents the description of the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='meta' type='wxr:meta' minOccurs='0' maxOccurs='unbounded'>
									<xs:annotation>
										<xs:documentation>
											Represents a single term meta associated with the WP_Term.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
							</xs:all>
						</xs:extension>
					</xs:complexContent>
				</xs:complexType>
			</xs:element>
			<xs:element name='link' minOccurs='0' maxOccurs='unbounded'>
				<xs:complexType>
					<xs:complexContent>
						<xs:extension base='wxr:open_content'>
							<xs:all>
								<xs:element name='id' type='xs:positiveInteger'/>
								<xs:element name='url' type='xs:anyURI'/>
								<xs:element name='name' type='wxr:key'/>
								<xs:element name='image' type='xs:anyURI'/>
								<xs:element name='target'>
									<xs:simpleType>
										<xs:restriction base='xs:string'>
											<xs:enumeration value='_blank'/>
											<xs:enumeration value='_top'/>
											<xs:enumeration value=''/>
										</xs:restriction>
									</xs:simpleType>
								</xs:element>
								<xs:element name='description' type='xs:string'/>
								<xs:element name='visible'>
									<xs:simpleType>
										<xs:restriction base='xs:string'>
											<xs:enumeration value='Y'/>
											<xs:enumeration value='N'/>
										</xs:restriction>
									</xs:simpleType>
								</xs:element>
								<xs:element name='owner' type='wxr:key'/>
								<xs:element name='rating' type='xs:int'/>
								<xs:element name='updated' type='wxr:date_time'/>
								<xs:element name='rel' type='xs:string'/>
								<xs:element name='notes' type='xs:string'/>
								<xs:element name='rss' type='xs:anyURI'/>
								<xs:element name='category' type='wxr:key' minOccurs='0' maxOccurs='unbounded'/>
							</xs:all>
						</xs:extension>
					</xs:complexContent>
				</xs:complexType>
			</xs:element>
		</xs:all>
	</xs:group>

	<xs:group name='post_elements'>
		<xs:annotation>
			<xs:documentation>
				This model group contains of the WXR elements that represent those parts of a WP_Post for which there is no standard
				RSS element.
			</xs:documentation>
		</xs:annotation>
		<xs:all>
			<xs:element name='id' type='xs:positiveInteger'>
				<xs:annotation>
					<xs:documentation>
						Represents the ID of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='date' type='wxr:date_time'>
				<xs:annotation>
					<xs:documentation>
						Represents the post_date of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='date_gmt' type='wxr:date_time'>
				<xs:annotation>
					<xs:documentation>
						Represents the post_date_gmt of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='comment_status' type='wxr:comment_ping_status'>
				<xs:annotation>
					<xs:documentation>
						Represents the comment_status of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='ping_status' type='wxr:comment_ping_status'>
				<xs:annotation>
					<xs:documentation>
						Represents the ping_status of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='name' type='wxr:key'>
				<xs:annotation>
					<xs:documentation>
						Represents the slug of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='status' type='xs:string'>
				<xs:annotation>
					<xs:documentation>
						Represents the post_status of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='parent' type='xs:nonNegativeInteger'>
				<xs:annotation>
					<xs:documentation>
						Represents the ID of the parent of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='menu_order' type='xs:int'>
				<xs:annotation>
					<xs:documentation>
						Represents the menu_order of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='type' type='wxr:post_type'>
				<xs:annotation>
					<xs:documentation>
						Represents the post_type of the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='password' type='xs:string'>
				<xs:annotation>
					<xs:documentation>
						Represents the post_password of the WP_Post.  Will be the empty string when the
						post is NOT password protected.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='is_sticky' type='wxr:boolean_as_int_string'>
				<xs:annotation>
					<xs:documentation>
						Represents whether the WP_Post is sticky.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='attachment_url' type='xs:anyURI' minOccurs='0'>
				<xs:annotation>
					<xs:documentation>
						Represents the URL for the WP_Post whose post_type is 'attachment'.  Will not be present if
						the post_type is not 'attachment.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='meta' type='wxr:meta' minOccurs='0' maxOccurs='unbounded'>
				<xs:annotation>
					<xs:documentation>
						Represents a single post meta associated with the WP_Post.
					</xs:documentation>
				</xs:annotation>
			</xs:element>
			<xs:element name='comment' minOccurs='0' maxOccurs='unbounded'>
				<xs:annotation>
					<xs:documentation>
						Represents a single WP_Comment associated with the WP_Post.
					</xs:documentation>
				</xs:annotation>
				<xs:complexType>
					<xs:complexContent>
						<xs:extension base='wxr:open_content'>
							<xs:all>
								<xs:element name='id' type='xs:positiveInteger'>
									<xs:annotation>
										<xs:documentation>
											Represents the ID of the WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='author' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_author of the WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='author_email' type='wxr:email'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_author_email of the WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='author_url' type='xs:anyURI'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_author_url of the WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='author_IP'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_author_IP of the WP_Comment.
										</xs:documentation>
									</xs:annotation>
									<xs:simpleType>
										<xs:restriction base='xs:string'>
											<xs:pattern value='\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}|'>
												<xs:annotation>
													<xs:documentation>
														This pattern matches an IPv4 IP address
														(or the empty string, which can sometimes occur).
													</xs:documentation>
												</xs:annotation>
											</xs:pattern>
										</xs:restriction>
									</xs:simpleType>
								</xs:element>
								<xs:element name='date' type='wxr:date_time'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_date of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='date_gmt' type='wxr:date_time'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_date_gmt of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='content' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_content of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='approved' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_approved of a WP_Comment.
										</xs:documentation>
										<xs:documentation>
											@todo Should the type of this element be a restriction
											of xs:string that enumerates the possible values?  At this
											time I'm not sure what the values for that enumeration
											would be so I'm leaving it as xs:string.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='type' type='xs:string'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_type of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='parent' type='xs:nonNegativeInteger'>
									<xs:annotation>
										<xs:documentation>
											Represents the comment_parent of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='user_id' type='xs:nonNegativeInteger'>
									<xs:annotation>
										<xs:documentation>
											Represents the user_id of a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
								<xs:element name='meta' type='wxr:meta' minOccurs='0' maxOccurs='unbounded'>
									<xs:annotation>
										<xs:documentation>
											Represents a single meta associated with a WP_Comment.
										</xs:documentation>
									</xs:annotation>
								</xs:element>
							</xs:all>
						</xs:extension>
					</xs:complexContent>
				</xs:complexType>
			</xs:element>
		</xs:all>
	</xs:group>

	<xs:complexType name='open_content' abstract='true'>
		<xs:annotation>
			<xs:documentation>
				This type serves as the base type for all WXR elements that have complexContent.
			</xs:documentation>
		</xs:annotation>
		<xs:openContent>
			<xs:any notNamespace='##local' processContents='lax'>
				<xs:annotation>
					<xs:documentation>
						Allow alements from any non-empty namespace (including the
						WXR namespace) to make forwards-compatible processing
						easier (to account for additions to WXR in future versions).
					</xs:documentation>
				</xs:annotation>
			</xs:any>
		</xs:openContent>
		<xs:all>
			<xs:annotation>
				<xs:documentation>
					This empty all model group exists only so that we can extend this
					type via an all group.  The need for this is a consequence of
					the rules for extension in XML Schema 1.1.
				</xs:documentation>
			</xs:annotation>
		</xs:all>
		<xs:anyAttribute processContents='lax'>
			<xs:annotation>
				<xs:documentation>
					Allow attributes from any namespace (including the empty namespace
					and the WXR namespace) to make forwards-compatible processing
					easier (to account for additions to WXR in future versions).
				</xs:documentation>
			</xs:annotation>
		</xs:anyAttribute>
	</xs:complexType>

	<xs:complexType name='meta'>
		<xs:annotation>
			<xs:documentation>
				Represents a single WP Meta (e.g., (post|term|comment|user)_meta).
			</xs:documentation>
		</xs:annotation>
		<xs:complexContent>
			<xs:extension base='wxr:open_content'>
				<xs:all>
					<xs:element name='key' type='wxr:key'>
						<xs:annotation>
							<xs:documentation>
								Represents the meta_key of the meta.
							</xs:documentation>
						</xs:annotation>
					</xs:element>
					<xs:element name='value' type='xs:string'>
						<xs:annotation>
							<xs:documentation>
								Represents the meta_value of the meta. 
							</xs:documentation>
						</xs:annotation>
					</xs:element>
				</xs:all>
			</xs:extension>
		</xs:complexContent>
	</xs:complexType>
</xs:schema>