# LV2 Persist Extension # Copyright (C) 2010 Leonard Ritter # Copyright (C) 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 persist: . @prefix doap: . @prefix foaf: . @prefix lv2: . @prefix rdf: . @prefix rdfs: . @prefix xsd: . a lv2:Specification ; doap:name "LV2 Persist" ; doap:maintainer [ a foaf:Person ; foaf:name "David Robillard" ; foaf:homepage ; rdfs:seeAlso ] ; rdfs:comment """ This extension provides a mechanism for plugins to save and restore state across instances, allowing hosts to save configuration/state/data with a project or fully clone a plugin instance (including internal state). The motivating idea behind this extension is that a plugin instance's state is entirely represented by port values and a single key/value dictionary. This makes state well-defined and easily manageable by hosts. Keys are URIs, avoiding conflicts and allowing the same dictionary to be used to store plugin state in any context. Values are typed tagged (by URI mapped integers), but otherwise are simple binary blobs. This extension defines plugin instance state and provides a mechanism for saving/restoring it, but otherwise makes no restrictions on how a plugin works with state. For example, other extensions may define dynamic ways to control plugin state at runtime. The idea is that all plugin state can be represented with a single (conceptual) dictionary. This state representation is tried-and-true, universal, and works well with many existing technologies. Accordingly, plugins/extensions that deal with instance state in any way SHOULD represent it in a way compatible with this extension, i.e. URI keys with URI-typed values. Similarly, plugins SHOULD NOT use any other mechanism to store/restore state; this will cause serious problems, don't do it! Note that you can store values of any format whatsoever, so if you have an existing state representation to use (e.g. XML), simply store it as a single value under some key. Files may be persisted using this extension in conjunction with the LV2 Files extension. Instance state as defined by this extension is RDF compatible, allowing for simple and seamless integration with existing technology (LV2 or otherwise). An obvious benefit of this is that plugin state can be elegantly described in Turtle files; the persist:instanceState predicate is provided for this purpose. RDF compatibility is also convenient since LV2 hosts are likely to already have mechanisms for working with RDF-style data. Note, however, that hosts may store state in any way, and are not required to use any specific technology or file format to support this extension. """ . persist:InstanceState a rdfs:Class ; rdfs:label "Plugin Instance State" ; rdfs:comment """ This class is used to express a plugin instance's state in RDF. The key/value properties of the instance form the predicate/object (respectively) of triples with a persist:InstanceState as the subject (see persist:instanceState for an example). This may be used wherever it is useful to express a plugin instance's state in RDF (e.g. for serialisation, storing in a model, or transmitting over a network). Note that this class is provided because it may be useful for hosts, plugins, or extensions that work with instance state, but its use is not required to support the LV2 Persist extension. """ . persist:instanceState a rdf:Property ; rdfs:range persist:InstanceState ; rdfs:comment """ Predicate to relate a plugin instance to an InstanceState. This may be used wherever the state of a particular plugin instance needs to be represented. Note that the domain of this property is unspecified, since LV2 does not define any RDF class for plugin instance. This predicate may be used wherever it makes sense to do so, e.g.: 
@prefix eg: <http://example.org/> .

<plugininstance> persist:instanceState [
    eg:somekey "some value" ;
    eg:someotherkey "some other value" ;
    eg:favouritenumber 2 .
]
Note that this property is provided because it may be useful for hosts, plugins, or extensions that work with instance state, but its use is not required to support the LV2 Persist extension. """ .