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+# LV2 Contexts Extension
+#
+# Allows for an LV2 plugin to have several independent contexts, each with its
+# own run callback and associated ports.
+#
+# Copyright (C) 2007-2010 David Robillard
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+
+@prefix ctx:  <http://lv2plug.in/ns/ext/contexts#> .
+@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
+@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .
+@prefix doap: <http://usefulinc.com/ns/doap#> .
+@prefix foaf: <http://xmlns.com/foaf/0.1/> .
+
+<http://lv2plug.in/ns/ext/contexts>
+	a lv2:Specification , lv2:Feature ;
+	doap:name "LV2 Contexts" ;
+	doap:shortdesc "Support for plugins with several execution contexts." ;
+	lv2:documentation """
+<p>An extension for LV2 plugins which have several execution contexts.</p>
+
+<p>Contexts allow plugins to run tasks and/or process input/output in
+multiple threads.  Contexts can be used to add non-realtime functionality
+to a plugin while still keeping the audio run() method realtime safe.</p>
+
+<p>A context is an LV2 feature, so the usual LV2 feature mechanism is used
+to determine whether a plugin has a given context, and whether or not it is
+mandatory.</p>
+
+<p>Unless otherwise stated, each context (defined by some URI) adds a new
+threading class similar to the Audio class defined by LV2.  Each context has a
+run callback and a connect_port callback both in the same class (i.e. can't be
+called concurrently), but may be called concurrently with functions for other
+contexts (excluding the Instantiation class).  Context properties such as
+ctx:hardRTCapable apply to both functions.
+The host MUST only call the correct connect_port function associated with the
+context for that port, i.e. it is an error to use the main LV2 connect_port
+function on a port with a context other than the main LV2 run function.</p>
+""" .
+
+
+##########################
+## Context Base Classes ##
+##########################
+
+ctx:Context a rdfs:Class ;
+	rdfs:label "LV2 Context" ;
+	lv2:documentation """
+<p>A potentially concurrent context (callback) on a plugin.</p>
+
+<p>Ports are always associated with a context.  If a port has no explicit context
+property, then its context is ctx:audioContext (the default LV2 run() context).</p>
+
+<p>A plugin indicates support for a context by supporting an LV2 Feature with
+that context's URI.  If a plugin optionally supports a context (e.g.
+<code>&lt;plugin&gt; lv2:optionalFeature ctx:idleContext .</code>), then
+all ports associated with that context MUST be lv2:connectionOptional.  Thus,
+hosts that do not support contexts will connect such ports to NULL and the
+plugin can run with only a standard LV2 run() context.</p>
+
+<p>Any plugin that supports any context (optionally or mandatorily) MUST adhere
+to the following additional threading rules for LV2_Descriptor.connect_port:</p>
+<ul>
+<li>connect_port MUST only be called for a given port from the context
+associated with that port</li>
+<li>connect_port MAY be called concurrently for ports with different
+contexts (but MUST NOT be called concurrently for multiple ports in the
+same context)</li>
+</ul>
+<p>Note this implies that any shared data access in connect_port may be
+accessed concurrently.  The plugin is responsible for any synchronisation
+or locking necessary to make this possible.</p>
+""" .
+
+ctx:audioContext a ctx:Context , lv2:Feature ;
+	rdfs:comment """The context of LV2_Descriptor.run().""" .
+
+ctx:messageContext a ctx:Context , lv2:Feature ;
+	lv2:documentation """
+<p>A non-realtime context for plugin control via message passing.  This context
+has a run method which takes a bitset of flags for parameters specifying which
+input and output ports are valid before and after the run method has executed,
+respectively (see <code>LV2_Contexts_MessageContext</code>).</p>
+""" .
+
+ctx:idleContext a ctx:Context , lv2:Feature ;
+	rdfs:comment """
+A non-realtime idle context, periodically run by the host roughly every second.
+This context never has any ports.
+""" .
+
+ctx:requestRunFeature a lv2:Feature ;
+	lv2:documentation """
+<p>A feature allowing the plugin to request the execution of a particular
+context at an arbitrary time.  To support this feature, the host MUST pass an
+LV2_Feature to <code>instantiate</code> with <code>data</code> pointing to a
+LV2_Contexts_Request_Run_Feature.</p>
+
+<p>The plugin MAY call <code>request_run</code> with the given
+<code>data</code> from any non-realtime context to demand soon-as-possible execution
+of the specified context.</p>
+""" .
+
+ctx:context a rdf:Property ;
+	rdfs:domain lv2:Port ;
+	rdfs:range  ctx:Context ;
+	rdfs:label  "is used in context" ;
+	rdfs:comment """
+The context a particular port is associated with; the port will only be
+connected/read/written by that context.
+
+If no context is specified, the port is considered part of the default LV2
+audio context.""" .
+
+