This vocabulary defines messages which can be used to access and manipulate properties. It is designed to provide a dynamic control interface for LV2 plugins, but is useful in many contexts.
The main feature of this design is that the messages themselves are described in the same format as the data they work with. In particular, messages can be serialised as a binary Object or in Turtle (or any other RDF serialisation).
The idea behind using a property-based interface for control is to prevent an an explosion of message types. Instead of a custom message for each action, control is achieved via manipulating properties (which are likely already defined for other reasons). Note, however, that this is purely conceptual; there is no requirement that the receiver actually implement a store of resources with properties.
For example, consider an object that can blink. Rather than define a
specific interface to control this (e.g. obj.start_blinking();
obj.stop_blinking()
), set a blinking
property to true or false
(e.g. obj.set(blinking, true)
) to achieve the desired behaviour.
One benefit of this approach is that a persistent state model is available
for free
: simply serialise the blinking
property.
This specification is strictly metadata and does not define any binary mechanism, though it can be completely expressed by standard types in the LV2 Atom extension. Thus, hosts can be expected to be capable of transmitting it between plugins, or between a plugin and its UI, making it a good choice for advanced plugin control.
""" . patch:Ack a rdfs:Class ; rdfs:subClassOf patch:Response ; rdfs:label "Ack" ; lv2:documentation """An acknowledgement that a request has been successfully processed. This is returned as a reply when a specific reply type is not necessary or appropriate.
""" . patch:Delete a rdfs:Class ; rdfs:subClassOf patch:Request ; rdfs:label "Delete" ; lv2:documentation """Request the subject(s) be deleted.
""" . patch:Error a rdfs:Class ; rdfs:subClassOf patch:Response ; rdfs:label "Error" ; lv2:documentation """A response indicating an error processing a request.
""" . patch:Get a rdfs:Class ; rdfs:subClassOf patch:Request ; rdfs:label "Get" ; lv2:documentation """Request a description of the subject.
The detail of the response is not specified, it may be a flat description of
all the properties of the subject, or a more expressive description with
several subjects. A good choice is a concise bounded description
,
i.e. a description which recursively includes all properties with blank node
values.
The response should have the same patch:subject property as the request, and a patch:body that is a description of that subject. For example:
<get-request> a patch:Get ; patch:subject <something> .
Could result in:
[] a patch:Response ; patch:request <get-request> ; patch:subject <something> ; patch:body [ eg:name "Something" ; eg:ratio 1.6180339887 ; ] .
Note the use of blank nodes is not required; the value of patch:body may be the actual resource node. Depending on the transport and syntax used this may be preferable. However, the patch:subject property is required regardless. For example, the same response could be written:
<something> eg:name "Something" ; eg:ratio 1.6180339887 . [] a patch:Response ; patch:request <get-request> ; patch:subject <something> ; patch:body <something> .""" . patch:Insert a rdfs:Class ; rdfs:subClassOf patch:Request ; rdfs:label "Insert" ; rdfs:subClassOf [ a owl:Restriction ; owl:cardinality 1 ; owl:onProperty patch:subject ] ; lv2:documentation """
Insert the patch:body at patch:subject. If the subject does not exist, it is created. If the subject does already exist, it is added to. This request only adds properties, it never removes them. The user must take care that multiple values are not set for properties which should only have one value.
""" . patch:Message a rdfs:Class ; rdfs:label "Message" . patch:Move a rdfs:Class ; rdfs:subClassOf patch:Request ; rdfs:label "Move" ; rdfs:subClassOf [ a owl:Restriction ; owl:cardinality 1 ; owl:onProperty patch:subject ] , [ a owl:Restriction ; owl:cardinality 1 ; owl:onProperty patch:destination ] ; lv2:documentation """Move the patch:subject to patch:destination. After this, patch:destination has the description patch:subject had prior to this request's execution, and patch:subject does not exist any more.It is an error if the subject does not exist or the destination already exists.
""" . patch:Patch a rdfs:Class ; rdfs:subClassOf patch:Request , [ a owl:Restriction ; owl:minCardinality 1 ; owl:onProperty patch:subject ] ; lv2:documentation """A method for modifying the properties of an object.
This method always has at least one patch:subject, and exactly one patch:add and patch:remove property. The value of patch:add and patch:remove are nodes which have the properties to add or remove from the subject(s), respectively. The special value patch:wildcard may be used as the value of a remove property to remove all properties with the given predicate. For example:
[] a patch:Patch ; patch:subject <something> ; patch:add [ eg:name "New name" ; eg:age 42 ; ] ; patch:remove [ eg:name "Old name" ; eg:age patch:wildcard ; # Remove all old eg:age properties ] .""" . patch:Put a rdfs:Class ; rdfs:subClassOf patch:Request ; rdfs:label "Put" ; rdfs:subClassOf [ a owl:Restriction ; owl:cardinality 1 ; owl:onProperty patch:subject ] ; lv2:documentation """
Put the patch:body as the patch:subject. If the subject does not already exist, it is created. If the subject does already exist, the patch:body is considered an updated version of it, and the previous version is replaced.
""" . patch:Request a rdfs:Class ; rdfs:label "Request" ; rdfs:subClassOf patch:Message ; lv2:documentation """A request. A request may have a patch:subject property, which indicates which resource the request applies to. The subject may be omitted in contexts where it is implicit (e.g. the recipient is the subject).
""" . patch:Response a rdfs:Class ; rdfs:subClassOf patch:Message ; rdfs:label "Response" ; lv2:documentation """A response to a method.
""" . patch:Set a rdfs:Class ; rdfs:subClassOf patch:Request , [ a owl:Restriction ; owl:cardinality 1 ; owl:onProperty patch:body ] ; lv2:documentation """A method for setting properties of an object to unique values.
This is a simplified version of patch:Patch which only makes sense for properties which have at most one value. This method always has at least one patch:subject, and exactly one patch:add property. All the properties of the value of patch:add are set on the subject, with all old values for those properties removed. For example:
[] a patch:Set ; patch:subject <something> ; patch:body [ eg:name "New name" ; eg:age 42 ; ] .
This method is equivalent to a patch:Patch where the patch:remove value has every property of patch:add but with wildcard values. For example, the above patch is equivalent to:
[] a patch:Patch ; patch:subject <something> ; patch:add [ eg:name "New name" ; eg:age 42 ; ] ; patch:remove [ eg:name patch:wildcard ; eg:age patch:wildcard ; ] ;""" . patch:add a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Message . patch:body a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Message ; lv2:documentation """
The body of a message.
The details of this property's value depend on the type of message it is a part of.
""" . patch:destination a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Message . patch:request a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Response ; rdfs:range patch:Request ; lv2:documentation """The request this is a response to.
""" . patch:subject a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Message . patch:remove a rdf:Property , owl:ObjectProperty , owl:FunctionalProperty ; rdfs:domain patch:Message . patch:wildcard a rdfs:Resource ; rdfs:comment """ A wildcard which matches any resource. This makes it possible to describe the removal of all values for a given property. """ .