path: root/lv2/lv2plug.in/ns/ext/atom/atom.ttl

# LV2 Atom Extension
# Copyright 2007-2012 David Robillard <d@drobilla.net>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

@prefix atom: <http://lv2plug.in/ns/ext/atom#> .
@prefix dcs:  <http://ontologi.es/doap-changeset#> .
@prefix doap: <http://usefulinc.com/ns/doap#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix lv2:  <http://lv2plug.in/ns/lv2core#> .
@prefix owl:  <http://www.w3.org/2002/07/owl#> .
@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix ui:   <http://lv2plug.in/ns/extensions/ui#> .
@prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .

<http://lv2plug.in/ns/ext/atom>
	a lv2:Specification ;
	rdfs:seeAlso <atom.h> ,
		<util.h> ,
		<forge.h> ,
		<../../meta/meta.ttl> ;
	doap:name "LV2 Atom" ;
	doap:shortdesc "A generic value container and several data types." ;
	doap:created "2007" ;
	doap:license <http://opensource.org/licenses/isc> ;
	doap:developer <http://drobilla.net/drobilla#me> ;
	doap:release [
		doap:revision "0.6" ;
		doap:created "2012-02-22" ;
		dcs:blame <http://drobilla.net/drobilla#me>
	] ;
	lv2:documentation """
<p>This extension defines a generic container for data, called an <q>Atom</q>,
and several basic Atom types which can be used to express structured data.
Atoms are (with one exception) Plain Old Data (POD), which means they can be
easily copied generically (e.g. using <code>memcpy</code>), and are suitable
for use in high-performance and real-time code.</p>

<p>Since Atom communication can be implemented generically, plugins that
understand some type can be used together in a host that does not understand
that type.  Similarly, plugins (such as routers, delays, or data stores) can
meaningfully process atoms of a type unknown to them.</p>

<p>Atoms can and should be used anywhere values of various types must be stored
or transmitted.  This extension defines a port type, atom:AtomPort, for
transmitting atoms via ports.  The atom:Sequence type in an atom:AtomPort
replaces the <a href="http://lv2plug.in/ns/ext/event">LV2 event</a>
extension.</p>

<p>The types defined in this extension should be powerful enough to express
almost any structure.  Implementations SHOULD build structures out of the types
provided here, rather than define new binary formats (e.g. use atom:Object
rather than a new C <code>struct</code> type).  New binary formats are an
implementation burden which harms interoperabilty, and should only be defined
where absolutely necessary.</p>

<p>Implementing this extension requires a facility for mapping URIs to
integers, such as the <a href="http://lv2plug.in/ns/ext/urid">LV2 URID</a>
extension.</p>
""" .

atom:cType
	a rdf:Property ,
		owl:DatatypeProperty ,
		owl:FunctionalProperty ;
	rdfs:label "C type" ;
	rdfs:domain rdfs:Class ;
	rdfs:range xsd:string ;
	rdfs:comment """
The identifier for a C type describing the in-memory representation of
an instance of this class.
""" .

atom:Atom
	a rdfs:Class ;
	rdfs:label "Atom" ;
	atom:cType "LV2_Atom" ;
	lv2:documentation """
<p>Abstract base class for all atoms.  An LV2_Atom has a 32-bit
<code>type</code> and <code>size</code> followed by a body of <code>size</code>
bytes.  Atoms MUST be 64-bit aligned.</p>

<p>All concrete Atom types (subclasses of this class) MUST define a precise
binary layout for their body.</p>

<p>The <code>type</code> field is the URI of an Atom type mapped to an integer.
Implementations SHOULD gracefully ignore, or pass through, atoms with unknown
types.</p>

<p>All atoms are POD by definition except references, which as a special case
have <code>type = 0</code>.  An Atom MUST NOT contain a Reference.  It is safe
to copy any non-reference Atom with a simple <code>memcpy</code>, even if the
implementation does not understand <code>type</code>.  Though this extension
reserves the type 0 for references, the details of reference handling are
currently unspecified.  A future revision of this extension, or a different
extension, may define how to use non-POD data and references.  Implementations
MUST NOT send references to another implementation unless the receiver is
explicitly known to support references (e.g. by supporting a feature).  The
atom with both <code>type</code> <em>and</em> <code>size</code> 0 is
<q>null</q>, which is not considered a Reference.</p>
""" .

atom:Chunk
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Chunk of memory" ;
	lv2:documentation """
<p>A chunk of memory with undefined contents.  This type is used to indicate a
certain amount of space is available.  For example, output ports with a
variably sized type are connected to a Chunk so the plugin knows the size of
the buffer available for writing.</p>
""" .

atom:Number
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Number" .

atom:Int
	a rdfs:Class ;
	rdfs:subClassOf atom:Number ;
	rdfs:label "Signed 32-bit integer" ;
	atom:cType "LV2_Atom_Int" .

atom:Long
	a rdfs:Class ;
	rdfs:subClassOf atom:Number ;
	rdfs:label "Signed 64-bit integer" ;
	atom:cType "LV2_Atom_Long" .

atom:Float
	a rdfs:Class ;
	rdfs:subClassOf atom:Number ;
	rdfs:label "32-bit IEEE-754 floating point number" ;
	atom:cType "LV2_Atom_Float" .

atom:Double
	a rdfs:Class ;
	rdfs:subClassOf atom:Number ;
	rdfs:label "64-bit IEEE-754 floating point number" ;
	atom:cType "LV2_Atom_Double" .

atom:Bool
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Boolean" ;
	atom:cType "LV2_Atom_Bool" ;
	rdfs:comment "An Int where 0 is false and any other value is true." .

atom:String
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "String" ;
	atom:cType "LV2_Atom_String" ;
	lv2:documentation """
<p>A UTF-8 encoded string.</p>

<p>The body of an LV2_Atom_String is a C string in UTF-8 encoding, i.e. an
array of bytes (<code>uint8_t</code>) terminated with a NULL byte
(<code>'\\0'</code>).</p>

<p>This type can be used for free-form strings, but in most cases it is better to
use atom:Literal since this supports a language tag or datatype.  Implementations
SHOULD NOT use atom:String unless translating the string does not make sense and
the string has no meaningful datatype.</p>
""" .

atom:Literal
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "String Literal" ;
	atom:cType "LV2_Atom_Literal" ;
	lv2:documentation """
<p>A UTF-8 encoded string literal, with an optional datatype or language.</p>

<p>This type is compatible with rdf:Literal and is capable of expressing a
string in any language or a value of any type.  A Literal has a
<code>datatype</code> and <code>lang</code> followed by string data in UTF-8
encoding.  The length of the string data in bytes is <code>size -
sizeof(LV2_Atom_Literal)</code>, including the terminating NULL character.  The
<code>lang</code> field SHOULD be a URI of the form
&lt;http://lexvo.org/id/iso639-3/LANG&gt; or
&lt;http://lexvo.org/id/iso639-1/LANG&gt; where LANG is a 3-character ISO 693-3
language code, or a 2-character ISO 693-1 language code, respectively.</p>

<p>A Literal may have a <code>datatype</code> OR a <code>lang</code>, but never
both.</p>

<p>For example, a Literal can be "Hello" in English:</p>
<pre class="c-code">
void set_to_hello_in_english(LV2_Atom_Literal* lit) {
     lit->atom.type = map(expand("atom:Literal"));
     lit->atom.size = 14;
     lit->datatype  = 0;
     lit->lang      = map("http://lexvo.org/id/iso639-1/en");
     memcpy(LV2_ATOM_CONTENTS(LV2_Atom_Literal, lit),
            "Hello",
            sizeof("Hello"));  // Assumes enough space
}
</pre>

<p>or a Turtle string:</p>
<pre class="c-code">
void set_to_turtle_string(LV2_Atom_Literal* lit, const char* ttl) {
     lit->atom.type = map(expand("atom:Literal"));
     lit->atom.size = 64;
     lit->datatype  = map("http://www.w3.org/2008/turtle#turtle");
     lit->lang      = 0;
     memcpy(LV2_ATOM_CONTENTS(LV2_Atom_Literal, lit),
            ttl,
            strlen(ttl) + 1);  // Assumes enough space
}
</pre>
""" .

atom:Path
	a rdfs:Class ;
	rdfs:subClassOf atom:String ;
	rdfs:label "File path string" ;
	lv2:documentation """
<p>A local file path string.  This is identical in format to atom:String,
except the string is a path.  Since the ability to distinguish paths from plain
strings is often necessary, paths MUST NOT be transmitted as atom:String.</p>
""" .

atom:URI
	a rdfs:Class ;
	rdfs:subClassOf atom:String ;
	rdfs:label "URI string" ;
	lv2:documentation """
<p>A URI string.  This is identical in format to atom:String, except the string
is a URI.  This is useful when a URI is needed but mapping is inappropriate,
for example with temporary or relative URIs.  Since the ability to distinguish
URIs from plain strings is often necessary, URIs MUST NOT be transmitted as
atom:String.</p>

<p>This is not strictly a URI, since UTF-8 is allowed.  Escaping and related
issues issues are the host's responsibility.</p>
""" .

atom:URID
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Integer ID mapped from a URI" ;
	atom:cType "LV2_Atom_ID" ;
	lv2:documentation """
<p>An unsigned 32-bit integer mapped from a URI (e.g. with LV2_URID_Map).</p>
""" .

atom:Vector
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Vector" ;
	atom:cType "LV2_Atom_Vector" ;
	lv2:documentation """
<p>A homogeneous series of atom bodies with equivalent type and size.</p>

<p>An LV2_Atom_Vector is a 32-bit <code>child_size</code> and
<code>child_type</code> followed by <code>size / child_size</code> atom
bodies.</p>

<p>For example, an atom:Vector containing 42 elements of type atom:Float:</p>
<pre class="c-code">
struct VectorOf42Floats {
    uint32_t size;        // sizeof(LV2_Atom_Vector_Body) + (42 * sizeof(float);
    uint32_t type;        // map(expand("atom:Vector"))
    uint32_t child_size;  // sizeof(float)
    uint32_t child_type;  // map(expand("atom:Float"))
    float    elems[42];
};
</pre>

<p>Note that it is possible to construct a valid Atom for each element
of the vector, even by an implementation which does not understand
<code>child_type</code>.</p>
""" .

atom:Tuple
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Tuple" ;
	lv2:documentation """
<p>A series of Atoms with varying <code>type</code> and <code>size</code>.</p>

<p>The body of a Tuple is simply a series of complete atoms, each aligned to
64 bits.</p>
""" .

atom:Property
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Property" ;
	atom:cType "LV2_Atom_Property" ;
	lv2:documentation """
<p>A property of an atom:Object.  An LV2_Atom_Property has a URID
<code>key</code> and <code>context</code>, and an Atom <code>value</code>.
This corresponds to an RDF Property, where the <q>key</q> is the <q>predicate</q>
and the <q>value</q> is the object.</p>

<p>The <code>context</code> field can be used to specify a different context
for each property, where this is useful.  Otherwise, it may be 0.</p>
""" .

atom:Object
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Object" ;
	atom:cType "LV2_Atom_Object" ;
	lv2:documentation """
<p>An <q>Object</q> is an atom with a set of properties.  This corresponds to
an RDF Resource, and can be thought of as a dictionary with URID keys.</p>

<p>An LV2_Atom_Object has a uint32_t <code>id</code> and uint32_t
<code>type</code>, followed by a series of atom:Property bodies (without
headers, i.e. LV2_Atom_Property_Body).  The LV2_Atom_Object::type field is
semantically equivalent to a property with key rdf:type, but is included in the
structure to allow for fast dispatch.</p>

<p>This is an abstract Atom type, an Object is always either a atom:Resource
or a atom:Blank.</p>
""" .

atom:Resource
	a rdfs:Class ;
	rdfs:subClassOf atom:Object ;
	rdfs:label "Resource" ;
	atom:cType "LV2_Atom_Object" ;
	lv2:documentation """
<p>An atom:Object where the <code>id</code> field is a URID, i.e. an Object
with a URI.</p>
""" .

atom:Blank
	a rdfs:Class ;
	rdfs:subClassOf atom:Object ;
	rdfs:label "Blank" ;
	atom:cType "LV2_Atom_Object" ;
	lv2:documentation """
<p>An atom:Object where the LV2_Atom_Object::id is a blank node ID (NOT a URI).
The ID of a Blank is valid only within the context the Blank appears in.  For
ports this is the context of the associated run() call, i.e. all ports share
the same context so outputs can contain IDs that correspond to IDs of blanks in
the input.</p>
""" .

atom:Sound
	a rdfs:Class ;
	rdfs:subClassOf atom:Vector ;
	rdfs:label "Sound" ;
	atom:cType "LV2_Atom_Sound" ;
	lv2:documentation """
<p>An atom:Vector of atom:Float which represents an audio waveform.  The format
is the same as the buffer format for lv2:AudioPort (except the size may be
arbitrary).  An atom:Sound inherently depends on the sample rate, which is
assumed to be known.</p>
""" .

atom:TimeUnit
	a rdfs:Class ;
	rdfs:label "Time Unit" ;
	lv2:documentation "<p>A unit for atom:Event time stamps.</p>" .

atom:frameTime
	a rdf:Property ,
		owl:DatatypeProperty ,
		owl:FunctionalProperty ;
	rdfs:range xsd:decimal ;
	rdfs:label "Frame time" ;
	lv2:documentation """
<p>Time stamp in audio frames.  Typically used for events.</p>
""" .

atom:beatTime
	a rdf:Property ,
		owl:DatatypeProperty ,
		owl:FunctionalProperty ;
	rdfs:range xsd:decimal ;
	rdfs:label "Beat time" ;
	lv2:documentation """
<p>Time stamp in beats.  Typically used for events.</p>
""" .

atom:Frames
	a rdfs:Class ;
	rdfs:subClassOf atom:TimeUnit ;
	rdfs:label "Frames" ;
	lv2:documentation """
<p>Time in audio frames.  Converting this to absolute time depends on the
sample rate.  When this is the stamp unit for an atom:Sequence, its events have
int64_t time stamps (<code>event.time.frames</code>)</p>
""" .

atom:Beats
	a rdfs:Class ;
	rdfs:subClassOf atom:TimeUnit ;
	rdfs:label "Beats" ;
	lv2:documentation """
<p>Time in beats.  Converting this to absolute time depends on the tempo.  When
this is the stamp unit for an atom:Sequence, the events in that sequence have a
<code>double</code> stamp (<code>event.time.beats</code>).</p>""" .

atom:Event
	a rdfs:Class ;
	rdfs:label "Event" ;
	atom:cType "LV2_Atom_Event" ;
	lv2:documentation """
<p>An atom with a time stamp header prepended, typically an element of an
atom:Sequence.  Note this is not an Atom type.</p>
""" .

atom:Sequence
	a rdfs:Class ;
	rdfs:subClassOf atom:Atom ;
	rdfs:label "Sequence" ;
	atom:cType "LV2_Atom_Sequence" ;
	lv2:documentation """
<p>A sequence of atom:Event, i.e. a series of time-stamped Atoms.</p>
""" .

atom:AtomPort
	a rdfs:Class ;
	rdfs:subClassOf lv2:Port ;
	rdfs:label "Atom Port" ;
	lv2:documentation """
<p>A port which contains an lv2:Atom.  Ports of this type are connected to an
LV2_Atom with a type specified by atom:bufferType.</p>

<p>Output ports with a variably sized type MUST be initialised by the host
before every run() to an atom:Chunk with size set to the available space.  The
plugin reads this size to know how much space is available for writing.  In all
cases, the plugin MUST write a complete atom (including header) to outputs.
However, to be robust, hosts SHOULD initialise output ports to a safe sentinel
(e.g. the null Atom) before calling run().</p>
""" .

atom:bufferType
	a rdf:Property ,
		owl:ObjectProperty ;
	rdfs:domain atom:AtomPort ;
	rdfs:label "Buffer type" ;
	lv2:documentation """
<p>Indicates that an AtomPort may be connected to a certain Atom type.  A port
MAY support several buffer types.  The host MUST NOT connect a port to an Atom
with a type not explicitly listed with this property.  The value of this
property MUST be a sub-class of atom:Atom.  For example, an input port that is
connected directly to an LV2_Atom_Double value is described like so:</p>

<pre class="turtle-code">
&lt;plugin&gt;
    lv2:port [
        a lv2:InputPort , atom:AtomPort ;
        atom:bufferType atom:Double ;
    ] .
</pre>

<p>This property only describes the types a port may be <em>directly</em>
connected to.  It says nothing about the expected contents of containers.  For
that, use atom:supports.</p>
""" .

atom:childType
	a rdf:Property ,
		owl:ObjectProperty ;
	rdfs:label "Child type" ;
	rdfs:comment "The type of a container's children." .

atom:supports
	a rdf:Property ;
	rdfs:label "Supports" ;
	lv2:documentation """
<p>Indicates that a particular Atom type is supported.</p>

<p>This property is defined loosely, it may be used to indicate that anything
<q>supports</q> an Atom type, wherever that may be useful.  It applies
<q>recursively</q> where collections are involved.</p>

<p>In particular, this property can be used to describe which event types are
supported or <q>understood</q> by a port.  For example, a port that receives
MIDI events is described like so:</p>

<pre class="turtle-code">
&lt;plugin&gt;
    lv2:port [
        a lv2:InputPort , atom:AtomPort ;
        atom:bufferType atom:Sequence ;
        atom:supports midi:MidiEvent ;
    ] .
</pre>
""" .

atom:eventTransfer
	a ui:PortProtocol ;
	lv2:documentation """
<p>Transfer of individual events in a port buffer.  Useful as the
<code>format</code> for a LV2_UI_Write_Function.</p>

<p>This protocol applies to ports which contain events, usually in an
atom:Sequence.  The host must transfer each individual event to the recipient.
The format of the received data is an LV2_Atom, there is no timestamp
header.</p>
""" .

atom:atomTransfer
	a ui:PortProtocol ;
	lv2:documentation """
<p>Transfer of the complete atom in a port buffer.  Useful as the
<code>format</code> for a LV2_UI_Write_Function.</p>

<p>This protocol applies to atom ports.  The host must transfer the complete
atom contained in the port, including header.</p>
""" .