Copyright © 2010 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
This specification defines a client-side API to access metadata information related to media resources on the Web. The overall purpose of the API is to provide developers with a convenient access to metadata information stored in different metadata formats. The API will be introduced in an abstract manner using the interface definition language Web IDL. Thereby, the Media Ontology Core Properties will be used as a pivot vocabulary in the API.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This is the second Working Draft of the API for Media Resource 1.0 specification. It has been produced by the Media Annotations Working Group, which is part of the W3C Video on the Web Activity.
Please send comments about this document to public-media-annotation@w3.org mailing list (public archive).
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
1 Introduction
1.1 Formats in scope
1.2 Formats out of scope
1.3 Terminology
2 API Description
2.1 Design consideration
2.2 API for identifying
the media resource and metadata
2.3 API for accessing
properties
2.3.1 Identification Properties
2.3.1.1 Identifier
2.3.1.2 Title
2.3.1.3 Language
2.3.1.4 Locator
2.3.2 Creation Properties
2.3.2.1 Contributor
2.3.2.2 Creator
2.3.2.3 CreateDate
2.3.2.4 Location
2.3.3 Content Properties
2.3.3.1 Description
2.3.3.2 Keyword
2.3.3.3 Genre
2.3.3.4 Rating
2.3.4 Relational
Properties
2.3.4.1 Relation
2.3.4.2 Collection
2.3.5 Rights Properties
2.3.5.1 Copyright
2.3.5.2 Policy
2.3.6 Distribution
Properties
2.3.6.1 Publisher
2.3.6.2 TargetAudience
2.3.7 Fragments
Properties
2.3.7.1 Fragments
2.3.7.2 NamedFragments
2.3.8 API for Technical
Properties
2.3.8.1 FrameSize
2.3.8.2 Compression
2.3.8.3 Duration
2.3.8.4 Format
2.3.8.5 Samplingrate
2.3.8.6 Framerate
2.3.8.7 Bitrate
2.3.8.8 NumTracks
2.4 API for retrieval of reason of an
error
2.5 API for iterating
2.5.1 getPropertyNamesWithValues
2.5.2 getSourceFormatsWithValues
2.5.3 getOriginalData
3 Examples of how to use the API
4 Security Considerations
A Web IDL description for API
B References(Normative)
C References(Non-Normative)
D Acknowledgements (Non-Normative)
This section is informative.
Editorial note | |
This part will be elaborated in the perspectives of reason why we want to provide an API and an explanation on who should use/implement it. |
This specification defines a client-side API to access metadata information related to media resources on the Web. The overall purpose of the API is to provide developers with a convenient access to metadata information stored in different metadata formats. Thereby, the Media Ontology Core Properties will be used as a pivot vocabulary in the API. The description of relations between these core properties and the metadata formats in scope (1.1 Formats in scope) are stored in the Media Ontology in order to provide cross-community data integration. The API will be introduced in an abstract manner using the interface definition language Web IDL. The decision to use Web IDL, which offers bindings for ECMAScript and Java, can be based on the Use Cases and Requirements for Ontology and API for Media Object 1.0. This document clearly states that the focus for this API lies on multimedia services on the Web.
The API serves as a mediator between a developer and the underlying Ontology for Media Resource 1.0 with the goal to support interoperability between metadata formats. It offers GET operations to retrieve particular metadata informations represented in a certain metadata format related to media ressources on the Web.
The initial version of this document contains only a limited description of API. In addtion, there are many open issues including definitions of return types. Nevertheless it is being published with the aspiration to gather wide feedback on the yet available API design.
Refers to the formats in scope of Ontology for Media Resource 1.0.
Refers to the Formats out of scope of Ontology for Media Resource 1.0.
In this document the terms "Media Resource", "Property", "Mapping" and "Property value type" are to be interpreted as defined in Section 2 of Ontology for Media Resource 1.0.
Editorial note | |
There are many open issues about SET interfaces, so these issues will be covered later. |
This part defines the interface for accessing the metadata. The API has been
described using Web IDL. All properties can
be accessed through a specific operation, encapsulated in the
MediaResource
interface within the mawg
module.
Currently, only read access is defined. When an attempt to read a property
fails, diagnostics information can be obtained using a diagnosis operation.
Certain properties have complex structures so the return type consists of one
or more object
types. The structure of these objects is still to
be defined, currently these follow different interfaces which have been defined
in the returnValues
module.
Note that, some of these interfaces inherit from the MAObject
interface and the Language
interface.
interface MAObject { attribute DOMString unstructuredValue; attribute DOMString uri; attribute DOMString sourceFormat; attribute DOMString fragmentIdentifier; attribute DOMString mappingType; }; interface Language { attribute DOMString language; };
The MAObject
interface has an attribute
unstructeredValue
using DOMString
. If it is not
clear how a certain value for a property should be structured, this
attribute allows to describe the value in plain text. A uri
attribute is provided which should hold an URI. This can for example be
used to represent labels as uri's. A language
attribute
allows to specify the language of the returned property. The
sourceFormat
attribute allows to specify the metadata source
from which the metadata was retrieved. The
fragmentIdentifier
attribute determins the fragment for
which the metadata is relevant. Lastly, the mappingType
attribute specifies the kind of mapping as discussed in the
semantic level mappings.
The Language
interface includes an attribute
language
that holds the language of the metadata.
We consider two scenarios where the API could be implemented: either in the user agent (scenario 1) or as a web service (scenario 2). The two scenarios are shown in the figure.
The API is implemented in the user agent (e.g., browser or browser plugin) and exposed as a JavaScript API (using the WebIDL JavaScript binding). The user agent includes the components for metadata access (possibly extraction) and mappings for a supported set of formats. The metadata sources (the media resource and/or metadata document(s)) must be retrievable and access (establish connection, retrieval) of the metadata sources is handled by the user agent.
The API is implemented as a Web service. Such an implementation would be typically used by a non-UI client, such as an agent harvesting metadata. However, the API could be also accessed from a user agent, and used the same way as described in scenario 1 by the help of a JavaScript library for accessing the web service. At the back-end of the web service, this scenario also allows supporting a media repository (e.g. content provider's archive database, movie store) from which the user agent could directly retrieve metadata sources and which might have a custom metadata format not supported by a user agent. In contrast to an integrated component (see scenario 1), an implementation of the API in a web service could do more complex mappings on the fly as a component integrated in a user agent, and can be more flexible (e.g., supporting additional formats).
In both scenarios, the access to the metadata properties needs the following stack of components:
An implementation of the API for Media Resource (as defined in this document), which providers the actual getter methods for the properties.
An implementation of the mappings from a specific source format to the properties of the media ontology (as defined in Ontology for Media Resource 1.0).
A format specific API to access the metadata. This is can be an API for accessing a metadata document describing a media resource (e.g. an XML parser and a set of XPath statements) or an extractor the read metadata embedded in the media resource (e.g. a library to read EXIF information from JPEG images). In order to define the context on which the API for Media Resource is working (cf. Section 2.2), it is assumed that there is at least a unidirectional reference from the media resource to the metadata document or vice versa. If this is not the case such a reference needs to be provided by the web application (scenario 1), web service (scenario 2) or media repository (scenario 2).
This part defines part of the interface for identifying the Media Resource for which the API will grant access to. One general operation is defined that allows access to the properties. The specific property is passed as an argument and a list of objects is returned that hold the values according to the requested property. Depending on the requested property, the returned objects follow a different interface. These are listed in the following sections.
boolean setContext(in DOMString mediaResource, in optional Object[] metadataSources );
The setContext
operation allows to set the specific
Media Resource and metadata sources for which the API applies. The
mediaResource
argument identifies the Media Resource. The
implementation of the API should try to find relevant metadata sources
for this Media Resource. Additionally, the metadataSources
argument allows to identify other metadata sources which should be
included by the API. This argument is an array of objects, each
implementing the MetadataSource
interface. This interface
holds an uri identifying the metadata source
(metadataSource
) and the name of the actual metadata format
(sourceFormat
). The return value of the operation is a
boolean stating whether the Media Resource and metadata sources were
succesfully loaded.
interface MetadataSource { attribute DOMString metadataSource; attribute DOMString sourceFormat; };
A boolean stating whether the Media Resource and metadata resources could be identified.
This part defines part of the interface for accessing the metadata that describes a Media Resource. One general operation is defined that allows access to the properties. The specific property is passed as an argument and a list of objects is returned that hold the values according to the requested property. Depending on the requested property, the returned objects follow a different interface. These are listed in the following sections.
MAObject[] getProperty(in DOMString propertyName, in optional DOMString sourceFormat, in optional DOMString subtype, in optional DOMString language, in optional DOMString fragment );
The getProperty
operation allows to retrieve the value
of a certain property. The propertyName
argument identifies
the property for which the values need to be retrieved. Optional
arguments allow to refine the request. The sourceFormat
identifies a specific metadata format. If a metadata format is defined,
only the metadata available in the corresponding metadata format are
retrieved. The subtype
argument identifies a subtype. Some
properties can be filtered on subtypes. The language
argument allows to identify the language of the metadata. Only if the
metadata is available in the specified language, the values are returned.
Finally, the fragment
argument allows to identify the
specific media fragment for which the metadata is requested.
An array of MAObjects
that hold the values of the
requested property.Depending on the requested property, these objects
implement a different interface. The next sections list the different
properties and the returned objects.
The identifier
property identifies a resource.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should represent a URI identifying the resource, the type
attribute holds the type of the identifier, which can be filtered on in
the getProperty
operation. Possible values are " UMID" and
"ISAN".
interface Identifier: MAObject { attribute DOMString value; attribute DOMString type; };
["http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=identifier
Response (JSON format): "identifier" : ["http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG"]
The title
property defines the title of the document,
or the name given to the resource.
An array of object
elements implementing the
Title
interface. The value
attribute should
hold the title as a plain string. Additionally, a type
describes the type of the title, which can be filtered on in the
getProperty
operation. Possibilities for this are "Album
title" and "Song title".
interface Title: MAObject, Language { attribute DOMString value; attribute DOMString type; };
["MAWG Stockholm 20090626",""]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=title
Response (JSON format): "title" : ["MAWG Stockholm 20090626"]
The language
property specifies a language used in the
entity, Recommended best practice is to use BCP 47 [BCP 47].
An array of object
elements implementing the
StringObject
interface. The value
attribute
should represent the language as a plain string.
interface StringObject: MAObject { attribute DOMString value; };
["en-us"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=language
Response (JSON format): "language" : ["en-us"]
The locator
property holds a URI at which the entity
can be accessed (e.g. a URL, or a DVB URI).
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold the URI.
interface StringObject: MAObject { attribute DOMString value; };
["http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=locator
Response (JSON format): "locator" : ["http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG"]
The contributor
property holds a pair identifying the
contributors and the nature of the contribution. E.g. actor, cameraman,
director, singer, author, artist (Note: subject see addition of
contributors type) identifies a resource.
An array of object
elements implementing the
Contributor
interface. This object has an attribute
id
which identifies the contributor. Additionally, the
role
attribute defines the role, which can be filtered on in
the getProperty
operation. For the latter a number of
suggested terms are defined:
editor (EBU 11.1)
actor (EBU 25.9)
composer
featured_in
cinematographer
director
musicproducer
producer
screenplayer
writer
distributor (company)
production company
interface Contributor: MAObject { attribute DOMString id; attribute DOMString role; };
[http://individuals.example.com/Contributor1, "editor"], [http://individuals.example.com/Contributor2, "producer"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=contributors
Response (JSON format): "contributors" : ["editor (EBU 11.1)", "actor (EBU 25.9)", "composer", "featured_in", "cinematographer", "director", "musicproducer", "producer", "screenplayer", "writer", "distributor (company)", "production company"]
The creator
property holds the authors of the resource
(listed in order of precedence, if significant).
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold an identifier for an author.
interface StringObject: MAObject { attribute DOMString value; };
["http://individuals.example.com/Author1", "http://individuals.example.com/Author2"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=creator
Response (JSON format): "creator" : ["http://individuals.example.com/Author1", "http://individuals.example.com/Author2"]
The createDate
property holds the date and time the
entity was originally created. (for commercial purpose there might be an
annotation of publication date).
An array of object
elements implementing the
Date
interface. The exact format of the date
attribute is currently undefined. It should hold a type
attribute defining the specific type of creation, which can be filtered
on in the getProperty
operation. Possibilities are "Create
Date" and "Publish Date".
interface Date: MAObject { attribute DOMString date; attribute DOMString type; };
[2009-06-26T15:30:00]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=createDate
Response (JSON format): "createDate" : ["2009-06-26T15:30:00"]
The location
property holds the location where the
resource has been shot/recorded.
An array of object
elements implementing the
Location
interface. The name
attribute holds a
free text name of the location. The longitude
,
latitude
, and altitude
determin the spatial
coordinates according to the system defined in system
.
interface Location: MAObject, Language { attribute DOMString name; attribute Float longitude; attribute Float latitude; attribute Float altitude; attribute DOMString system; };
["San Jose", 37.33986481118008, -121.88507080078125, 0, "GPS"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=location
Response (JSON format): "location" : ["San Jose", 37.33986481118008, -121.88507080078125, 0, "GPS"]
The description
property holds a textual description of
the content of the resource.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold a description of the content of the media resource.
interface StringObject: MAObject, Language { attribute DOMString value; };
["Group picture of the W3C Media Annotations WG at the face-to-face meeting in Stockholm."]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=description
Response (JSON format): "description" : ["Group picture of the W3C Media Annotations WG at the face-to-face meeting in Stockholm."]
The keyword
property represents a keyword that
specifies the topic of the content of the resource.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold one keyword.
interface StringObject: MAObject, Language { attribute DOMString value; };
["W3C Media Annotations WG", "meeting", "group picture"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=keyword
Response (JSON format): "keyword" : ["W3C Media Annotations WG", "meeting", "group picture"]
The genre
property describes the genre of the
entity.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should represent the genre of the media resource.
interface StringObject: MAObject, Language { attribute DOMString value; };
["Work"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=genre
Response (JSON format): "genre" : ["Work"]
Editorial note | |
It should be clarified about what the 'context' of a rating is |
The rating
property holds information to identify the
rating person or organization and the rating (real value). Additionally,
a minimum and maximum value can be given. Lastly, information on the
context of the rating is also included.
An array of object
elements implementing the
Rating
interface. This object holds an attribute
issuer
to identify the rating person or organization. Next,
the rating value
can be represented, together with the
minimum
and maximum
rating values. These allow
to interpret the rating value. Lastly, a textual description of the
context
can be given. A type
attribute
determines the type of the rating, which can be filtered on in the
getProperty
operation. Possibilities are "Review Rating",
"MPAA", "Personal Rating"
interface Rating: MAObject, Language { attribute DOMString issuer; attribute short value; attribute short minimum; attribute short maximum; attribute DOMString type; };
["http://individuals.example.com/ChrisPoppe", 10.0, 0, 10.0, "Personal Rating"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=rating
Response (JSON format): "rating" : ["http://individuals.example.com/ChrisPoppe", 10.0, 0, 10.0, "Personal Rating"]
The relation
property holds pairs identifying the
entities and the nature of the realtionships. E.g. transcript,
original_work.
An array of object
elements implementing the
Relation
interface. This object holds an attribute
id
to identify the entitiy. A textual description of the
relationship is represented using the relationship
attribute, which can be filtered on in the getProperty
operation. For the latter a number of suggested terms are defined:
version of
reference
sound tracks
influenced by
re-edit
adapted_work
translated
interpretation
followed by
similar theme
similar touch
is similar to
nominated award
origin country
interface Relation: MAObject { attribute DOMString id; attribute DOMString relationship; };
["http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626_thumb.JPG", "re-edit"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=relation
Response (JSON format): "relation" : ["http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626_thumb.JPG", "re-edit"]
The collection
property holds a name of the collection
from wich the entities originates.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold the name of the collection from which the media resource
originates.
interface StringObject: MAObject, Language { attribute DOMString value; };
["My Work Pictures"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=collection
Response (JSON format): "collection" : ["My Work Pictures"]
The copyright
property holds the copyright statement
and an identification of the copyrights holder (DRM is out of scope for
MAWG).
An array ofobject
elements implementing the
Copyright
interface. This object holds an attribute
statement
that holds the copyright statement. An array of
DOMString
elements is used to denote the copyright holders
and stored in attribute holder
.
interface Copyright: MAObject, Language { attribute DOMString statement; attribute DOMString[] holder; };
["All images in the collection are copyrighted by John Doe", "http://individuals.example.com/JohnDoe"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=rights-properties
Response (JSON format): "rights-properties" : ["All images in the collection are copyrighted by John Doe", "http://individuals.example.com/JohnDoe]"
Editorial note | |
license/statement attribute: is this really free text? |
The policy
property holds a description of the
rights-related information regarding the media resource.
An array of object
elements implementing the
Policy
interface. This object holds an attribute
policy
that holds the description of the license. Attribute
organization
identifies the organization that issued the
license. Lastly, the type
holds the actual type of the
policy, which can be filtered on in the getProperty
operation. Current possibilities are "license", "access", and
"privacy".
interface Policy: MAObject, Language { attribute DOMString policy; attribute DOMString organization; attribute DOMString type; };
["Attribution 2.5 ", "http://creativecommons.org/licenses/by/2.5"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=policy
Response (JSON format): "policy" : ["Attribution 2.5 ", "http://creativecommons.org/licenses/by/2.5"]
The publisher
property holds identification of the
publisher of the entitiy. Examples of a Publisher include a person, an
organization, or a service. Typically, the name of a Publisher should be
used to indicate the entity.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should represent the name of the publisher.
interface StringObject: MAObject, Language { attribute DOMString value; };
["http://individuals.example.com/JohnDoe"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=publisher
Response (JSON format): "publisher" : ["http://individuals.example.com/JohnDoe"]
The targetAudience
property holds a pair identifying
the issuer of the classification (agency) and the classification. E.g.
parental guide, targeted geographical region. Lastly, a type
attribute defines the type of the classification. Possible values are
"Age group" and "Geographical".
An array of object
elements implementing the
TargetAudience
interface. This object has an attribute
issuer
which identifies the issuer of the classification.
Additionally, the classification
attribute defines the
actual classification. Lastly, a type
attribute determins
the type of the classification, which can be filtered on in the
getProperty
operation. Possibilities include "Age group" and
"Geographical".
interface TargetAudience: MAObject, Language { attribute DOMString issuer; attribute DOMString classification; attribute DOMString type; };
[http://www.fosi.org/icra,"no nudity", "Age Group"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=targetaudience
Response (JSON format): "targetaudience" : [http://www.fosi.org/icra,"no nudity", "Age Group"]
The fragments
property holds a list of pairs of
fragment role and fragment identifier (e.g. chapters, favourite
scenes).
An array of object
elements implementing the
Fragment
interface. This object holds an attribute
role
that holds the role of the fragment. The attribute
identifier
is used to identify the fragment.
interface Fragment: MAObject { attribute DOMString role; attribute DOMString identifier; };
[["Person", "http://www.example.com/movie.mov#xywh=320,320,40,100"],
["Person", "http://www.example.com/movie.mov#xywh=300,350,40, 40"]]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=fragments
Response (JSON format): "fragments" : [["Person", "http://www.example.com/movie.mov#xywh=320,320,40,100"],["Person", "http://www.example.com/movie.mov#xywh=300,350,40, 40"]]
The namedFragments
property holds the list of named
fragments annotated for this resource (pairs of label and fragment
identifier).
An array of object
elements implementing the
NamedFragment
interface. This object holds an attribute
name
with the name given to the fragment. The attribute
identifier
is used to identify the fragment.
interface NamedFragment: MAObject { attribute DOMString name; attribute DOMString identifier; };
[["Joakim Söderberg", "http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG#xywh=1600,550,80,150]",
["Chris Poppe", "http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG#xywh=1400,600,80, 80]]"
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=namedFragments
Response (JSON format): "namedfragments" : [["Joakim Söderberg", "http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG#xywh=1600,550,80,150"], ["Chris Poppe", "http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626.JPG#xywh=1400,600,80, 80"]]
This part defines the interfaces for accessing the technical metadata that describe information for dealing with the creation or storage encoding processes or formats of the resource.
The frameSize
property determines the frame size.
An array of object
elements implementing the
FrameSize
interface. This object has an attribute
width
and height
to represent the width and
height of the frame, respectively.
interface FrameSize: MAObject { attribute unsigned long width; attribute unsigned long height; };
[3.072, 2.304]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=technical-properties
Response (JSON format): "technical-properties" : [3.072, 2.304]
The compression
property holds the compression type
used. Note: it might be possible to use extended mime type, see RFC
4281.
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold the compression type as a plain string.
interface StringObject: MAObject, Language { attribute DOMString value; };
["H.264/AVC"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=compression
Response (JSON format): "compression" : ["H.264/AVC"]
The duration
property represents the duration of the
entitiy.
An array of object
elements implementing the
FloatObject
interface. The value
attribute
should represent the duration (in secs).
interface FloatObject: MAObject { attribute unsigned long value; };
[3600]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=duration
Response (JSON format): "duration" : [3600]
The format
property holds the MIME type of the entity
(wrapper, bucket media types).
An array of object
elements implementing the
StringObject
interface. The value
attribute
should hold the MIME type as a plain string.
interface StringObject: MAObject, Language { attribute DOMString value; };
A DOMString
representing the MIME type.
["image/jpeg"]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=format
Response (JSON format): "format" : ["image/jpeg"]
The samplingrate
property holds the samplingrate of an
audio file. Only applicable for audio.
An array of object
elements implementing the
UnsignedLongObject
interface. The value
attribute should represent the samplingrate (in Hz).
interface UnsignedLongObject: MAObject { attribute unsigned long value; };
[100]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=samplingrate
Response (JSON format): "samplingrate" : [100]
The framerate
property holds the frame rate of the
video. Only applicable for video.
An array of object
elements implementing the
FloatObject
interface. The value
attribute
should represent the framerate (in fps).
interface FloatObject: MAObject { attribute float value; };
[30]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=framerate
Response (JSON format): "framerate" : [30]
Editorial note | |
Should bitrate be a number? What about Variable Bit Rate? Or would we raise NoValue in that case? |
The bitrate
property holds the average bitrate. Only
applicable for audio and video.
An array of object
elements implementing the
FloatObject
interface. The value
attribute
should represent the bitrate (in kbps).
interface FloatObject: MAObject { attribute float value; };
[100]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=bitrate
Response (JSON format): "bitrate" : [100]
The numTracks
property holds the number of tracks.
An array of object
elements implementing the
UnsignedShortObject
interface. The value
attribute should represent the number of tracks.
interface StringObject: MAObject { attribute unsigned short value; };
[2]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=numtracks
Response (JSON format): "numtracks" : [2]
This part defines part of the interface that allows to retrieve the reason for an error.
DOMString getDiagnosis();
This operation allows to retrieve the reason for an error (e.g., the
getProperty
operation returning a null value).
A DOMString
representing the reason for the last
error.
["Property undefined for this media type."]
Usage as a service:
Request: http://example.com/my-media-resource/?ma-query=numtracks&getDiagnosis=
Response (JSON format): "getDiagnosis" : ["Property undefined for this media type."]
This part defines part of the interface for iterating over the available metadata for a Media Resource.
DOMString[] getPropertyNamesWithValues(in optional DOMString sourceFormat, in optional DOMString language, in optional DOMString fragment);
This operation allows to retrieve all property names for which
metadata is available. If this operation returns a property name, this
means that a call to the getProperty
operation with the
corresponding property name will return at least one object.
An array of DOMStrings
representing the names of the
properties that will return values when accessed throug the
getProperty
operation.
["identifier", "title"]
Usage as a service:
Request: http://example.com/my-media-resource/?getPropertyNamesWithValues=
Response (JSON format): "getPropertyNamesWithValues" : ["identifier", "title"]
DOMString[] getSourceFormatsWithValues(in optional DOMString language);
This operation allows to retrieve all source formats for which
metadata is available. If this operation returns a source format, this
means that a call to the getProperty
operation with the
corresponding source format will return at least one object.
An array of DOMStrings
representing the names of the
source formats that will return values when accessed throug the
getProperty
operation.
["MPEG-7", "EXIF"]
Usage as a service:
Request: http://example.com/my-media-resource/?getSourceFormatsWithValues=
Response (JSON format): "getSourceFormatsWithValues" : ["MPEG-7", "EXIF"]
DOMString[] getOriginalData(in DOMString sourceFormat);
This operation allows to retrieve the original metadata according to the specified source format.
An array of DOMStrings
that hold the original metadata.
Each DOMString corresponds to one metadata source. The type of the
metadata depends on the source format (e.g., XML for MPEG-7, binary code
for EXIF).
["<?xml version="1.0"?> <metadata xmlns="http://example.org/myapp/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://example.org/myapp/ http://example.org/myapp/schema.xsd" xmlns:dc="http://purl.org/dc/elements/1.1/"> <dc:title>DC title</dc:title></metadata>"]
Usage as a service:
Request: http://example.com/my-media-resource/?getOriginalData=
Response (JSON format): "getOriginalData" : ["<?xml version="1.0"?> <metadata xmlns="http://example.org/myapp/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://example.org/myapp/ http://example.org/myapp/schema.xsd" xmlns:dc="http://purl.org/dc/elements/1.1/"> <dc:title>DC title</dc:title></metadata>"]
Editorial note | |
This part will illustrate how to use the API in the actual (working) implementations |
This section is informative.
Editorial note | |
It is required to be considered in the perspectives of developer, user and content’s provider. This will be revised with more security issues. |
This specification defines a client-side API to access metadata information related to media resources on the Web. These APIs will provide the methods for getting and setting metadata information which can be in one of different formats, either as separate document or embedded in media resources. So far concerning the setting method, there could be security consideration issues.
There are related activity and technical documents in W3C such as Policy Requirements in DAP WG, ODRL 1.1, P3P 1.1 and PLING Wiki.
module mawg { interface MediaResource { //Media Resource context boolean setContext(in DOMString mediaResource, in optional Object[] metadataSources ); // Property Access object[] getProperty(in DOMString propertyName, in optional DOMString sourceFormat, in optional DOMString subtype, in optional DOMString language, in optional DOMString fragment ); //Iterating DOMString[] getPropertyNamesWithValues(in optional DOMString sourceFormat, in optional DOMString language, in optional DOMString fragment); DOMString[] getSourceFormatsWithValues(in optional DOMString language); DOMString getOriginalData(in DOMString sourceFormat); //Operation for retrieval of the reason of an error DOMString getDiagnosis(); }; interface MetadataSource { attribute DOMString metadataSource; attribute DOMString sourceFormat; }; module returnValues { interface MAObject { attribute DOMString unstructuredValue; attribute DOMString uri; attribute DOMString sourceFormat; attribute DOMString fragmentIdentifier; attribute DOMString mappingType; }; interface Language { attribute DOMString language; }; interface StringObject: MAObject, Language { attribute DOMString value; }; interface UnsignedLongObject: MAObject { attribute unsigned long value; }; interface UnsignedShortObject: MAObject { attribute unsigned short value; }; interface FloatObject: MAObject { attribute float value; }; interface Identifier: MAObject { attribute DOMString value; attribute DOMString type; }; interface Title: MAObject, Language { attribute DOMString value; attribute DOMString type; }; interface Contributor: MAObject { attribute DOMString id; attribute DOMString role; }; interface Date: MAObject { attribute DOMString date; attribute DOMString type; }; interface Location: MAObject, Language { attribute DOMString name; attribute Float longitude; attribute Float latitude; attribute Float altitiude; attribute DOMString system; }; interface Rating: MAObject, Language { attribute DOMString issuer; attribute short value; attribute short minimum; attribute short maximum; attribute DOMString context; attribute DOMString type; }; interface Relation: MAObject, Language { attribute DOMString id; attribute DOMString relationship; }; interface Copyright: MAObject, Language { attribute DOMString statement; attribute DOMString[] holder; }; interface Policy: MAObject, Language { attribute DOMString statement; attribute DOMString organization; attribute DOMString type; }; interface TargetAudience: MAObject, Language { attribute DOMString issuer; attribute DOMString classification; }; interface Fragment: MAObject, Language { attribute DOMString role; attribute DOMString identifier; }; interface NamedFragment: MAObject, Language { attribute DOMString name; attribute DOMString identifier; }; interface FrameSize: MAObject { attribute unsigned long width; attribute unsigned long height; }; }; };
This document is the work of the W3C Media Annotations Working Group.
Members of the Working Group are (at the time of writing, and by alphabetical order): Werner Bailer (K-Space), Tobias Bürger (University of Innsbruck), Eric Carlson (Apple, Inc.), Pierre-Antoine Champin ((public) Invited expert), Jaime Delgado (Universitat Politècnica de Catalunya), Jean-Pierre EVAIN ((public) Invited expert), Ralf Klamma ((public) Invited expert), WonSuk Lee (Electronics and Telecommunications Research Institute (ETRI)), Véronique Malaisé (Vrije Universiteit), Erik Mannens (IBBT), Hui Miao (Samsung Electronics Co., Ltd.), Thierry Michel (W3C/ERCIM), Frank Nack (University of Amsterdam), Soohong Daniel Park (Samsung Electronics Co., Ltd.), Silvia Pfeiffer (W3C Invited Experts), Chris Poppe (IBBT), Víctor Rodríguez (Universitat Politècnica de Catalunya), Felix Sasaki (Potsdam University of Applied Sciences), David Singer (Apple, Inc.), Joakim Söderberg (ERICSSON), Thai Wey Then (Apple, Inc.), Ruben Tous (Universitat Politècnica de Catalunya), Raphaël Troncy (CWI), Vassilis Tzouvaras (K-Space), Davy Van Deursen (IBBT).
The people who have contributed to discussions on public-media-annotation@w3.org are also gratefully acknowledged.