Metadata API for Media Resources 1.0 (original) (raw)

W3C

W3C Recommendation 13 March 2014

This version:

http://www.w3.org/TR/2014/REC-mediaont-api-1.0-20140313/

Latest published version:

http://www.w3.org/TR/mediaont-api-1.0/

Previous version:

http://www.w3.org/TR/2013/PR-mediaont-api-1.0-20131015/

Editors:

Florian Stegmaier, University of Passau

Werner Bailer, JOANNEUM RESEARCH

Martin Höffernig, JOANNEUM RESEARCH

이원석(Wonsuk Lee), Samsung Electronics, Ltd.

Chris Poppe, Ghent University

Please refer to the errata for this document, which may include some normative corrections.

See also translations.

Copyright © 2014 W3C® (MIT,ERCIM,Keio, Beihang), All Rights Reserved. W3C liability,trademark and document use rules apply.

Abstract

This specification defines an API to access metadata information related to media resources on the Web. The overall purpose is to provide developers with a convenient access to metadata information stored in different metadata formats. The API provides means to access the set of metadata properties defined in the Ontology for Media Resources 1.0 specification. These properties are used as a pivot vocabulary in this API. The core of this specification is the definition of API interfaces for retrieving metadata information in synchronous and asynchronous modes. It also defines interfaces for structured return types along with the specification of the behavior of an API implementation.

Status of This Document

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 document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

This document has been produced by the Media Annotations Working Group, which is part of the W3C Video on the Web Activity.

The public is encouraged to send comments on this Recommendation to the public mailing list public-media-annotation@w3.org (public archive). Use "[REC Comment API]" in the subject line of your email.

The Working Group has adopted a public test suite and has produced an implementation report for this Metadata API for Media Resources 1.0.

No changes to this document have been made since the previous version.

The Metadata API for Media Resources may be implemented in both client-only (built into a browser, as a plugin or as a JavaScript library) and client-server (server-side as a Web Service). The level of implementation of this API in these two scenario summarized in the implementation report allowed to exit Candidate Recommendation. Nevertheless this API is not expected to be implemented natively in the browser code.

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.

Table of Contents

1. Introduction

This specification defines an API to access metadata information related to media resources on the Web. The overall purpose is to provide developers with a convenient access to metadata information stored in different metadata formats. The core properties, defined in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_], will be used as a pivot vocabulary in this API. The description of relations between these core properties and the metadata formats in scope are documented in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_] in order to provide cross-community data integration. This API is described using the interface definition language Web IDL [WEBIDL]. The decision to use Web IDL, which offers bindings for ECMAScript and Java, is based on the Use Cases and Requirements for Ontology and Metadata API for Media Resources 1.0 [MEDIA-ANNOT-REQS].

This API defines interfaces that enable users/applications to consume metadata in an interoperable manner. Interoperability between metadata formats is ensured by the use of the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_] as pivot metadata format. This API offers operations to request particular metadata information represented in a certain metadata format related to media resources on the Web. Further it specifies the actual representation of the core properties and the behaviour of this API.

1.1 Formats in scope

Refers to the formats in scope of the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_].

1.2 Formats out of scope

Refers to the Formats out of scope of the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_].

1.3 Terminology

In this document the terms "Ontology", "Media Resource", "Property", "Mapping" and "Property value types" are to be interpreted as defined in Section 2 of the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_].

2. Conformance

In addition to sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The keywords must, must not, required,should, should not, recommended,may, and optional in this specification are to be interpreted as described in [RFC2119].

3. Design consideration

This section discusses different usage scenarios that led to design of the API. We consider two main scenarios, where this API be implemented and invoked:

In both client-only and client-server cases of the implementation, the media resources and/or the metadata sources are in many cases remote. The API is by default specified as an asynchronous API, i.e., the calls are not blocking, but results (or errors) are returned using a callback mechanism. In order to better support the Web Service case, a synchronous mode is also defined. The synchronous mode is optional.

The two scenarios are shown in Figure 1.

Diagram showing 2 scenarios with different usage of the API.

Figure 1: Two scenarios with different usage of this API.

This specification only defines the Metadata API for Media Resources. Other components depicted in Figure 1 (e.g., access/extraction/storage of metadata) are not covered.

Scenario 1: Client-only (User agent)

In the first scenario, this API is implemented in the user agent, i.e. built into a browser, as a plugin or as a JavaScript library. Here, there exist three possibilities to invoke the API: by an external calling code, an internal calling code behaving like a client or it is attached as an extension to a user agent. Usually, such implementations are an example for asynchronous processing. Besides the Metadata API for Media Resources 1.0, the user agent may include components for metadata access (and extraction) and mappings for a supported set of formats, e.g., as defined in the property mapping table of the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_]. Further, the metadata sources (the media resource and/or metadata document(s)) must be retrievable. The access (e.g., establish connection, retrieval) to the metadata sources is handled by the user agent.

Scenario 2: Client-Server

In the second scenario, this API is implemented as a Web Service following the principles of server-side synchronous processing. Such an implementation would be typically used by a non-UI client, such as an agent harvesting metadata. However, this API can be also accessed from a user agent, and used the same way as described in scenario 1 with the help of a client-side library for accessing the Web Service. In the implementation of the Web Service, this scenario also allows supporting a media repository, e.g., content provider's archive database, movie store. With the help of such a service the user agent can retrieve metadata sources, 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 this API in a web service can do more complex mappings on the fly than a component integrated in a user agent, and can be more flexible (e.g., supporting additional formats).

In both scenarios, the API serves as a mediator between a client application and the actual metadata sources. Interoperability is ensured by defining i) operations for accessing the metadata information, ii) a common object structure and iii) API behaviour (e.g., status codes). Following this, an implementation has to implement this stack of components:

This API provides access to metadata information stored in different metadata formats. As such, different instances of the same property can exist.

4. API Description

This API defines a number of interfaces using [WEBIDL]. These can be grouped in the following categories:

Next, the different interfaces and exposed operations are discussed. Implementations of this API must support asynchronous mode of operation, may support the synchronous one and must support the interfaces defined in this document. Instead of exceptions, a status code indicating the state of processing (see Section 4.7) is returned (in the synchronous API) or provided via a callback function (in the asynchronous API) in case an error occurs.

Then, the interfaces for the return types, i.e., MediaAnnotation and its specializations, and MetadataSource are defined.

The IDL fragment in Appendix A of this specification must be interpreted as required for conforming IDL fragments, as described in the “Web IDL” specification. [WEBIDL]

4.1 MediaResource interface

The MediaResource interface is the core of this API and provides operations to access the metadata properties of a specific media resource. Here, a clear separation between asynchronous and synchronous mode of operation has been achieved by defining two implementing interfaces (derived from MediaResource), the AsyncMediaResource and the SyncMediaResource interface. Objects of these interfaces will be created by calling createMediaResource of the MediaResource interface. The actual connection to a specified metadata source will be created with the execution of thegetMediaProperty operation of AsyncMediaResource or SyncMediaResource interface. The mediaResource argument identifies the media resource, for which the implementation of this API should try to find relevant metadata sources. Optionally, references to metadata sources can be passed using an array of objects, each implementing the MetadataSource interface (see Section 4.6).

interface MediaResource { short getSupportedModes (); MediaResource createMediaResource (DOMString mediaResource, optional MetadataSource[] metadataSources, optional short mode); };

4.1.1 Methods

createMediaResource

This operation instantiates an object of either AsyncMediaResource or SyncMediaResource interface. Further, it allows to set the specific media resource and metadata sources to which this API is applied.

Parameter Type Nullable Optional Description
mediaResource DOMString ✘ ✘ This attribute must set the specific media resource that should be processed by the API.
metadataSources MetadataSource[] ✘ ✔ This attribute should specify additional metadata sources.
mode short ✘ ✔ This attribute should specify the desired mode of operation. 1 for asynchronous and 2 for synchronous mode should be used. In the case the mode argument is omitted, and the implementation supports both modes, the asynchronous mode will be used.

No exceptions.

Return type: [MediaResource](#idl-def-MediaResource)

getSupportedModes

This operation is called to identify the implemented mode. The return codes should be as follows: **1** for asynchronous, **2** for synchronous and **3** for both modes.

No parameters.

No exceptions.

4.1.2 Examples in Javascript

Example for getSupportedModes:

ma = new MediaResource(); var mode = ma.getSupportedModes();

Example for createMediaResource:

metadataSources = new MetadataSource[2]; metadataSources[0] = new MetadataSource( "http://www.w3.org/2008/WebVideo/Annotations/drafts/metadata_formats/DC_example1.xml","dc"); metadataSources[1] = new MetadataSource( "http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG","exif");

mediaResource = new MediaResource();

if (mediaResource.getSupportedModes() == 1 || mediaResource.getSupportedModes() == 3) { aSyncObject = mediaResource.createMediaResource( "http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG", metadataSources, 1);

} else if (mediaResource.getSupportedModes() == 2 || mediaResource.getSupportedModes() == 3) { syncObject = mediaResource.createMediaResource( "http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG", metadataSources, 2); }

4.2 AsyncMediaResource interface

The AsyncMediaResource interface provides a number of operations that allow accessing the metadata of a media resource. This interface must be implemented.

Next, we give the Web IDL description of the AsyncMediaResource interface and describe the different operations that are part of it.

In this section the MediaAnnotations interface is used in the interface definitions. It serves as a container to hold general values about properties enabling an iteration over a set of different properties. Its definition can be found in Section 4.4

interface AsyncMediaResource : MediaResource { void getMediaProperty (DOMString[] propertyNames, PropertyCallback successCallback, ErrorCallback errorCallback,
       optional DOMString fragment, optional DOMString sourceFormat, optional DOMString language); void getOriginalMetadata (DOMString sourceFormat, MetadataCallback successCallback, ErrorCallback errorCallback); };

4.2.1 Methods

getMediaProperty

This operation allows retrieval of the value of a specific property, several or all properties in an asynchronous manner. The specific property is passed as an argument and a list of objects is returned that hold the values according to the requested property. These objects implement the MediaAnnotation interface, described in Section 4.4. Depending on the requested property, the returned objects implement a different subtypes (inheriting from the MediaAnnotation interface). For example, requesting "title" gives back an array of objects implementing the Title interface, requesting "creator" results in objects implementing the Creator interface and so on. These interfaces are described in Section 4.5. An example can be found here.

Parameter Type Nullable Optional Description
propertyNames DOMString[] ✘ ✘ This argument identifies an array containing the properties for which the values need to be retrieved. For an empty array all properties carrying values will be retrieved.
successCallback PropertyCallback ✘ ✘ This argument holds a callback object for asynchronous requests to the property. The successCallback object implements the PropertyCallback interface and holds a handleEvent operation that needs to be called once all data for the requested property is gathered. This handleEvent operation needs to be called with a new MediaAnnotation array.
errorCallback ErrorCallback ✘ ✘ This argument holds a callback object for failure of asynchronous requests to the property. TheerrorCallback object implements the ErrorCallback interface and holds a handleEvent operation that needs to be called if an attempt fails. This handleEvent operation needs to be called with a new DOMString representing the status code of the error (see Section 4.7 for details).
fragment DOMString ✘ ✔ This argument contains a URI identifying the specific media fragment for which the metadata is requested. The URI must conform to the URI for Media Fragment [MEDIA-FRAGMENTS] specification. This parameter is optional.
sourceFormat DOMString ✘ ✔ This argument identifies a specific metadata format. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_]. If a metadata format is defined, only the metadata available in the specified metadata format are retrieved. This parameter is optional.
language DOMString ✘ ✔ This argument allows to identify the language of the metadata. Values for the metadata will only be returned if it is available in the specified language. Recommended best practice is to use BCP 47 [BCP47]. This parameter is optional.

No exceptions.

Return type: void

getOriginalMetadata

This operation allows retrieval of the original metadata according to the specified source format in an asynchronous manner. An example can be found here.

Parameter Type Nullable Optional Description
sourceFormat DOMString ✘ ✘ This argument identifies a specific metadata format. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_]. If a metadata format is defined, only the metadata available in the specified metadata format are retrieved.
successCallback MetadataCallback ✘ ✘ This argument holds a callback object for asynchronous requests for the original metadata. The successCallback object implements the MetadataCallback interface and holds a handleEvent operation that needs to be called once all properties having values are listed. This handleEvent operation needs to be called with a new DOMString array holding the original metadata.
errorCallback ErrorCallback ✘ ✘ This argument holds a callback object for failure of asynchronous requests for the original metadata. The errorCallback object implements the ErrorCallback interface and holds a handleEvent operation that needs to be called if an attempt fails. This handleEvent operation needs to be called with a new DOMString representing the status code of the error (see Section 4.7 for details).

No exceptions.

Return type: void

4.2.2 Callback interfaces

4.2.2.1 PropertyCallback interface

The PropertyCallback interface holds a handleEvent operation that needs to be called once all data for the requested property has been gathered.

interface PropertyCallback { void handleEvent (MediaAnnotation[] mediaAnnotations); };

4.2.2.1.1 Methods

handleEvent

This operation is called when all data is gathered corresponding to a request for values of one or more properties.

Parameter Type Nullable Optional Description
mediaAnnotations MediaAnnotation[] ✘ ✘ This argument holds a list of objects with values according to the requested property. These objects implement the MediaAnnotation interface, described in Section 4.4. Depending on the requested property, the returned objects implement a different subtypes (inheriting from the MediaAnnotation interface).

No exceptions.

Return type: void

4.2.3 Examples in Javascript

Example for asynchronous getMediaProperty:

aSyncMediaResource = mediaResource.createMediaResource("http://www.imdb.com/title/tt0133152/", new Array(), 1); aSyncMediaResource.getMediaProperty(["title"], successCallback, errorCallback, "", "", "");

function successCallback(MediaAnnotation[] mediaAnnotations) { ... }

function errorCallback(DOMString error) { ... }

Example for asynchronous getOriginalMetadata :

aSyncMediaResource = mediaResource.createMediaResource( "http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG", new Array(), 1); aSyncMediaResource.getOriginalMetadata("dc", successCallback, errorCallback);

function successCallback(DOMString[] metadata) { ... }

<metadata xmlns='http://example.org/myapp/'

dc:title

function errorCallback(DOMString error) { ... }

4.3 SyncMediaResource interface

The SyncMediaResource interface provides a number of operations to access the metadata of a media resource. This interface_may_ be implemented.

Next, we give the Web IDL description of the SyncMediaResource interface for synchronous requests and describe the different operations that are part of it. The MediaResource defines a constructor that can be called to construct the object based on an identifier of the media resource and optionally some metadata sources.

interface SyncMediaResource : MediaResource { MediaAnnotation[] getMediaProperty (DOMString[] propertyNames, optional DOMString fragment,
       optional DOMString sourceFormat, optional DOMString language); DOMString[] getOriginalMetadata (DOMString sourceFormat); };

4.3.1 Methods

getMediaProperty

This operation allows retrieval of the metadata of a specific property, several or all properties in a synchronous manner. The passed array holds the requested properties and an array of objects is returned. If the array is empty, every property holding values will be requested and returned. The returned objects implement theMediaAnnotation interface (see Section 4.3). Depending on the requested property, the returned objects implement different subtypes (inheriting from the MediaAnnotation interface). For example, requesting "title" gives back an array of objects implementing the Title interface, requesting "creator" results in objects implementing the Creator interface and so on. These subtypes are described in Section 4.4. The operation returns a MediaAnnotation array holding the requested properties. If an error occurs during retrieval, a MediaAnnotation object with the corresponding status code (e.g., 400, 404 or 415) will be generated and inserted at the first position of the array. An example can be found here.

In this section the MediaAnnotations interface is used in the interface definitions. It serves as a container to hold general values about properties enabling an iteration over a set of different properties. Its explanation can be found in Section 4.4

Parameter Type Nullable Optional Description
propertyNames DOMString[] ✘ ✘ This argument holds the requested properties as an array. If the array is empty, each property holding values will be returned.
fragment DOMString ✘ ✔ This argument contains a URI identifying the specific media fragment for which the metadata is requested. The URI must conform to the URI for Media Fragment [MEDIA-FRAGMENTS] specification. This parameter is optional.
sourceFormat DOMString ✘ ✔ This argument identifies a specific metadata format. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_]. If a metadata format is defined, only the metadata available in the specified metadata format is retrieved. This parameter is optional.
language DOMString ✘ ✔ This argument allows to identify the language of the metadata. Values for the metadata will only be returned if it is available in the specified language. Recommended best practice is to use BCP 47 [BCP47]. This parameter is optional.

No exceptions.

Return type: [MediaAnnotation](#idl-def-MediaAnnotation)[]

getOriginalMetadata

This operation allows retrieval of the original metadata according to the specified source format in a synchronous manner. The operation returns a DOMString array holding the status code of the request at the first and the original metadata at the second position. An example can be found here.

Parameter Type Nullable Optional Description
sourceFormat DOMString ✘ ✘ This argument identifies a specific metadata format. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [_MEDIA-ONTOLOGY_]. If a metadata format is defined, only the metadata available in the specified metadata format is retrieved.

No exceptions.

4.3.2 Examples in Javascript

The examples in this section use getMediaProperty() to get an object implementing the MediaAnnotation interface. The noErrorStatus function ensures that no error is present and the requested properties carry values.

We give some JavaScript examples on how to use the synchronous MediaResource interface and it's operations.

Example for synchronous getMediaProperty:

syncMediaResource = mediaResource.createMediaResource("http://www.imdb.com/title/tt0133152/", new Array(), 2); title = syncMediaResource.getMediaProperty(["title"], "", "", "");

if (noErrorStatus(title[0].statusCode) == true) { ... }

Example for synchronous getOriginalMetadata:

syncMediaResource = mediaResource.createMediaResource("http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG", new Array(), 2); dcMetadata = syncMediaResource.getOriginalMetadata("DC");

if (noErrorStatus(dcMetadata[0].statusCode) == true) { ... }

<metadata xmlns='http://example.org/myapp/'

dc:title

4.4 MediaAnnotation interface

MediaAnnotation interface is used as the return type ofMediaResource.getMediaProperty operation. It is a container for holding general values about metadata properties.

As several metadata properties are defined as complex types, specific derived types of MediaAnnotation have been defined, adding their specific attributes. However, MediaAnnotation can be used as a generic return type to access a printable string representation of the property (in the value attribute). It also includes a status code. In case of general errors, the first element of the returned MediaAnnotation array contains the global error code, otherwise the status can be given for each of the returned properties.

The following design considerations have been used for specifying the derived interfaces for each of the metadata properties:

interface MediaAnnotation { attribute DOMString propertyName; attribute DOMString value; attribute DOMString language; attribute DOMString sourceFormat; attribute DOMString fragmentIdentifier; attribute DOMString mappingType; attribute short statusCode; };

4.4.1 Attributes

fragmentIdentifier of type DOMString

This attribute should be an URI determining the fragment for which the metadata is relevant.

No exceptions.

language of typeDOMString

This attribute should hold the language of the metadata. The attribute is empty if language is not applicable for a specific property. Recommended best practice is to use BCP 47 [BCP47].

No exceptions.

mappingType of type DOMString

This attribute specifies the kind of mapping as discussed in the semantic level mappings. The value of this attribute should be one of the mapping characteristics.

No exceptions.

propertyName of type DOMString

The name of the property must be specified and should correspond to the property names defined in the Ontology for Media Resources 1.0 specification_[MEDIA-ONTOLOGY]._

sourceFormat of type DOMString

This attribute allows to specify the metadata source from which the metadata was retrieved. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

No exceptions.

statusCode of type short

This attribute must specify the status code for the associated property (e.g., 264 indicating a structured return value).

No exceptions.

value of type DOMString

This attribute must be filled with an printable string representation.

No exceptions.

4.4.2 Example in JavaScript

The noErrorStatus function ensures that no error is present and the requested properties carry values. The MediaAnnotation interface will be never instantiated - only instances of the derived interfaces will be created. These must be filled at least with the parameters specified in the MediaAnnotation interface and may be filled with the specific attributes.

mediaAnnotation = image.getMediaProperty(["title"], "", "", "");

if (noErrorStatus(mediaAnnotation[0].statusCode) == true) {
... }

http://www.example.com/video.ogv#t=10,20

4.5 Properties

This section describes the different properties that can be requested through the MediaResource.getMediaProperty() operation. When invoking this operation, objects implementing the MediaAnnotation interface are returned that represent the specified property. All properties are represented with an interface inherited from the MediaAnnotation interface (following the design guidelines described above).

Several of the following return type interfaces can hold the value of the property as both URI (i.e., a pointer to a controlled vocabulary) or as free text. The URI is preferred, and the respective attribute of the MediaAnnotation interface (or specialized type) shall be filled whenever possible (i.e., when the information is included in or can be constructed from the source metadata).

In the following, for each property, a (synchronous) JavaScript example illustrates the usage of the property specific attributes. In any case, the general attributes of the MediaAnnotation interface could be also requested.

4.5.1 Identification Properties

4.5.1.1 Identifier

When the MediaResource.getMediaProperty operation is invoked with "identifier" as a value of the propertyNames parameter, an object implementing the Identifier interface is returned representing the identifier property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Identifier : MediaAnnotation { attribute DOMString identifierLink; };

4.5.1.1.1 Attributes

identifierLink of type DOMString

This attribute holds a URI identifying the media resource.

No exceptions.

4.5.1.1.2 Example in JavaScript

id = image.getMediaProperty(["identifier"]);

4.5.1.2 Title

When the MediaResource.getMediaProperty operation is invoked with "title" as a value of the propertyNames parameter, an object implementing the Title interface is returned representing the title property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Title : MediaAnnotation { attribute DOMString titleLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

4.5.1.2.1 Attributes

titleLabel of type DOMString

This attribute holds the title as a plain string.

No exceptions.

typeLabel of type DOMString

This attribute holds the type of the title as a plain string.

No exceptions.

typeLink of type DOMString

This attribute holds the type of the title as a URI.

No exceptions.

4.5.1.2.2 Example in JavaScript

title = song.getMediaProperty(["title"]);

http://www.ebu.ch/metadata/cs/ebu_ObjectTypeCodeCS.xml#21

4.5.1.3 Language

When the MediaResource.getMediaProperty operation is invoked with "language" as a value of the propertyNames parameter, an object implementing the Language interface is returned representing the language property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Language : MediaAnnotation { attribute DOMString languageLink; attribute DOMString languageLabel; };

4.5.1.3.1 Attributes

languageLabel of type DOMString

This attribute represents the language of the media resource as a plain string, which can be filtered on in the getMediaProperty operation. Recommended best practice is to use BCP 47 [BCP47].

No exceptions.

languageLink of type DOMString

This attribute represents the language of the media resource as a URI.

No exceptions.

4.5.1.3.2 Example in JavaScript

language = video.getMediaProperty(["language"]);

4.5.1.4 Locator

When the MediaResource.getMediaProperty operation is invoked with "locator" as a value of the propertyNames parameter, an object implementing the Locator interface is returned representing the locator property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Locator : MediaAnnotation { attribute DOMString locatorLink; };

4.5.1.4.1 Attributes

locatorLink of type DOMString

This attribute specifies the location of the media resource by a URI.

No exceptions.

4.5.1.4.2 Example in JavaScript

locator = image.getMediaProperty(["locator"]);

http://www.w3.org/2008/WebVideo/Annotations/wiki/images/9/93/MAWG-Stockholm-20090626.JPG

4.5.2 Creation Properties

4.5.2.1 Contributor

When the MediaResource.getMediaProperty operation is invoked with "contributor" as a value of the propertyNames parameter, an object implementing the Contributor interface is returned representing the contributor property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Contributor : MediaAnnotation { attribute DOMString contributorLink; attribute DOMString contributorLabel; attribute DOMString roleLink; attribute DOMString roleLabel; };

4.5.2.1.1 Attributes

contributorLabel of type DOMString

This attribute represents the contributor (i.e., the agent making the contribution) as a plain string

No exceptions.

contributorLink of type DOMString

This attribute represents the contributor (i.e., the agent making the contribution) as a URI.

No exceptions.

roleLabel of type DOMString

This attribute represents the role of the contributor as a plain string.

No exceptions.

roleLink of typeDOMString

This attribute represents the role of the contributor as URI.

No exceptions.

4.5.2.1.2 Example in JavaScript

contributor = video.getMediaProperty(["contributor"]);

http://en.wikipedia.org/wiki/Tim_Burton

http://www.imdb.com/name/nm0000318/

4.5.2.2 Creator

When the MediaResource.getMediaProperty operation is invoked with "creator" as a value of the propertyNames parameter, an object implementing the Creator interface is returned representing the creator property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

interface Creator : MediaAnnotation { attribute DOMString creatorLink; attribute DOMString creatorLabel; attribute DOMString roleLink; attribute DOMString roleLabel; };

4.5.2.2.1 Attributes

creatorLabel of type DOMString

This attribute represents the creator (i.e., the agent participating in the creation of the media resource) as a plain string.

No exceptions.

creatorLink of type DOMString

This attribute represents the creator (i.e., the agent participating in the creation of the media resource) as a URI.

No exceptions.

roleLabel of type DOMString

This attribute represents the role of the creator as a plain string.

No exceptions.

roleLink of type DOMString

This attribute represents the role of the creator as URI.

No exceptions.

4.5.2.2.2 Example in JavaScript

creator = video.getMediaProperty(["creator"]);

http://dbpedia.org/resource/William_Shakespeare

http://www.ebu.ch/metadata/cs/ebu_RoleCodeCS.xml#22.5

4.5.2.3 MADate

When the MediaResource.getMediaProperty operation is invoked with "date" as a value of the propertyNames parameter, an object implementing the Date interface is returned representing the date property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]). This property has been renamed from "Date" into "MADate" in order to avoid naming conflicts with other objects named "Date" in web applications.

interface MADate : MediaAnnotation { attribute DOMString date; attribute DOMString typeLink; attribute DOMString typeLabel; };

4.5.2.3.1 Attributes

date of type DOMString

This attribute represents a date related to the media resource. A date value must be represented using one of the specific date/time data types of XML Schema, depending on the available precision: gYear gYearMonth, date, dateTime, or dateTimeStamp.

No exceptions.

typeLabel of type DOMString

This attribute defines the category of date (e.g. creation date, broadcast date, release date, date recorded and date edited) as a plain string.

No exceptions.

typeLink of type DOMString

This attribute defines the category of date (e.g. creation date, broadcast date, release date, date recorded and date edited) as a URI.

No exceptions.

4.5.2.3.2 Example in JavaScript

maDate = video.getMediaProperty(["date"]);

4.5.2.4 Location

When the MediaResource.getMediaProperty operation is invoked with "location" as a value of the propertyNames parameter, an object implementing the Location interface is returned representing the location property (defined inthe Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Location : MediaAnnotation { attribute DOMString locationLink; attribute DOMString locationLabel; attribute double longitude; attribute double latitude; attribute double altitude; attribute DOMString coordinateSystemLabel; attribute DOMString coordinateSystemLink; };

4.5.2.4.1 Attributes

altitude of type double

This attribute holds the altitude of the location, w.r.t. the coordinate system specified by the coordiateSystem attribute.

No exceptions.

coordinateSystemLabel of type DOMString

This attribute identifies the coordinate system used by its name.

No exceptions.

coordinateSystemLink of type DOMString

This attribute identifies the coordinate system used by a URI.

No exceptions.

latitude of type double

This attribute holds the latitude of the location, w.r.t. the coordinate system specified by the coordiateSystem attribute.

No exceptions.

locationLabel of type DOMString

This attribute identifies the location by its name as a plain string.

No exceptions.

locationLink of type DOMString

This attribute identifies the location as a URI.

No exceptions.

longitude of typedouble

This attribute holds the longitude of the location, w.r.t. the coordinate system specified by the coordiateSystem attribute.

No exceptions.

4.5.2.4.2 Example in JavaScript

location = video.getMediaProperty(["location"]);

http://en.wikipedia.org/wiki/San_Jose,_California

http://www.w3.org/2003/01/geo/wgs84_pos#Point

4.5.3 Content Properties

4.5.3.1 Description

When the MediaResource.getMediaProperty operation is invoked with "description" as a value of the propertyNames parameter, an object implementing the Description interface is returned representing the description property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Description : MediaAnnotation { attribute DOMString descriptionLabel; };

4.5.3.1.1 Attributes

descriptionLabel of type DOMString

This attribute contains a description of the content of the media resource.

No exceptions.

4.5.3.1.2 Example in Javascript

description = image.getMediaProperty(["description"]);

4.5.3.2 Keyword

When the MediaResource.getMediaProperty operation is invoked with "keyword" as a value of the propertyNames parameter, an object implementing the Keyword interface is returned representing the keyword property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Keyword : MediaAnnotation { attribute DOMString keywordLabel; attribute DOMString keywordLink; };

4.5.3.2.1 Attributes

keywordLabel of type DOMString

This attribute contains a keyword describing the content as a plain string.

No exceptions.

keywordLink of type DOMString

This attribute contains a URI representing a keyword describing the content.

No exceptions.

4.5.3.2.2 Example in Javascript

keyword = image.getMediaProperty(["keyword"]);

http://sw.opencyc.org/2008/06/10/concept/en/MeetingWithOrganizationalOutsiders

http://purl.org/vocabularies/princeton/wn30/synset-standardization-noun-1

4.5.3.3 Genre

When the MediaResource.getMediaProperty operation is invoked with "genre" as a value of the propertyNames parameter, an object implementing the Genre interface is returned representing the genre property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Genre : MediaAnnotation { attribute DOMString genreLabel; attribute DOMString genreLink; };

4.5.3.3.1 Attributes

genreLabel of type DOMString

This attribute represents the genre of the media resource as a plain string.

No exceptions.

genreLink of type DOMString

This attribute represents the genre of the media resource as a URI.

No exceptions.

4.5.3.3.2 Example in Javascript

genre = image.getMediaProperty(["genre"]);

http://www.ebu.ch/metadata/cs/ebu_ContentGenreCS.xml#3.1.1.9

4.5.3.4 Rating

When the MediaResource.getMediaProperty operation is invoked with "rating" as a value of the propertyNames parameter, an object implementing the Rating interface is returned representing the rating property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Rating : MediaAnnotation { attribute double ratingValue; attribute DOMString ratingSystemLabel; attribute DOMString ratingSystemLink; attribute double minimum; attribute double maximum; };

4.5.3.4.1 Attributes

maximum of type double

This attribute specifies the maximum rating value in the rating system.

No exceptions.

minimum of type double

This attribute specifies the minimum rating value in the rating system.

No exceptions.

ratingSystemLabel of type DOMString

This attribute identifies the rating system by a plain string.

No exceptions.

ratingSystemLink of type DOMString

This attribute identifies the rating system as a URI.

No exceptions.

ratingValue of type double

This attribute contains the value of the rating.

No exceptions.

4.5.3.4.2 Example in Javascript

rating = image.getMediaProperty(["rating"]);

http://individuals.example.com/JohnDoe

4.5.4 Relational Properties

4.5.4.1 Relation

When the MediaResource.getMediaProperty operation is invoked with "relation" as a value of the propertyNames parameter, an object implementing the Relation interface is returned representing the relation property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Relation : MediaAnnotation { attribute DOMString targetLink; attribute DOMString targetLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

4.5.4.1.1 Attributes

targetLabel of type DOMString

This attribute identifies the related resource by a plain string.

No exceptions.

targetLink of type DOMString

This attribute identifies the related resource by a URI.

No exceptions.

typeLabel of typeDOMString

This attribute specifies the type of relationship by a plain string.

No exceptions.

typeLink of type DOMString

This attribute specifies the type of relationship by a URI.

No exceptions.

4.5.4.1.2 Example in Javascript

relation = image.getMediaProperty(["relation"]);

http://www.w3.org/2008/WebVideo/Annotations/wiki/Image:MAWG-Stockholm-20090626_thumb.JPG

http://www.ebu.ch/metadata/cs/ebu_HowRelatedCS.xml#19

4.5.4.2 Collection

When the MediaResource.getMediaProperty operation is invoked with "collection" as a value of the propertyNames parameter, an object implementing the Collection interface is returned representing the collection property (defined inthe Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Collection : MediaAnnotation { attribute DOMString collectionLink; attribute DOMString collectionLabel; };

4.5.4.2.1 Attributes

collectionLabel of type DOMString

This attribute holds the name of the collection from which the media resource originates as a plain string.

No exceptions.

collectionLink of type DOMString

This attribute holds the name of the collection from which the media resource originates as URI.

No exceptions.

4.5.4.2.2 Example in Javascript

collection = image.getMediaProperty(["collection"]);

http://individuals.example.com/JohnDoe/myWorkPictures/

4.5.5 Rights Properties

When the MediaResource.getMediaProperty operation is invoked with "copyright" as a value of the propertyNames parameter, an object implementing the Copyright interface is returned representing the copyright property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Copyright : MediaAnnotation { attribute DOMString copyrightLabel; attribute DOMString holderLabel; attribute DOMString holderLink; };

4.5.5.1.1 Attributes

copyrightLabel of type DOMString

This attribute contains the copyright statement as a plain string.

No exceptions.

holderLabel of type DOMString

This attribute identifies the copyright holder by a plain string.

No exceptions.

holderLink of type DOMString

This attribute identified the copyright holder by a URI.

No exceptions.

4.5.5.1.2 Example in Javascript

copyright = image.getMediaProperty(["copyright"]);

http://individuals.example.com/JohnDoe

4.5.5.2 Policy

When the MediaResource.getMediaProperty operation is invoked with "policy" as a value of the propertyNames parameter, an object implementing the Policy interface is returned representing the policy property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Policy : MediaAnnotation { attribute DOMString statementLink; attribute DOMString statementLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

4.5.5.2.1 Attributes

statementLabel of type DOMString

This attribute contains a plain string of the policy statement.

No exceptions.

statementLink of type DOMString

This attribute contains a URI of the policy statement.

No exceptions.

typeLabel of type DOMString

This attribute identifies the type of the policy as a URI as a plain string.

No exceptions.

typeLink of type DOMString

This attribute identifies the type of the policy as a URI.

No exceptions.

4.5.5.2.2 Example in Javascript

policy = image.getMediaProperty(["policy"]);

http://creativecommons.org/licenses/by/2.5/

4.5.6 Distribution Properties

4.5.6.1 Publisher

When the MediaResource.getMediaProperty operation is invoked with "publisher" as a value of the propertyNames parameter, an object implementing the Publisher interface is returned representing the publisher property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Publisher : MediaAnnotation { attribute DOMString publisherLink; attribute DOMString publisherLabel; };

4.5.6.1.1 Attributes

publisherLabel of type DOMString

This attribute represents the publisher as a plain string.

No exceptions.

publisherLink of type DOMString

This attribute represents the publisher as a URI.

No exceptions.

4.5.6.1.2 Example in Javascript

publisher = image.getMediaProperty(["publisher"]);

http://company.example.com/ACME

4.5.6.2 TargetAudience

When the MediaResource.getMediaProperty operation is invoked with "targetAudience" as a value of the propertyNames parameter, an object implementing the TargetAudience interface is returned representing the targetAudience property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface TargetAudience : MediaAnnotation { attribute DOMString audienceLink; attribute DOMString audienceLabel; attribute DOMString classificationSystemLink; attribute DOMString classificationSystemLabel; };

4.5.6.2.1 Attributes

audienceLabel of type DOMString

This attribute identifies the target audience by a plain string.

No exceptions.

audienceLink of type DOMString

This attribute identifies the target audience by a URI.

No exceptions.

classificationSystemLabel of type DOMString

This attribute specifies the classification system by a plain string.

No exceptions.

classificationSystemLink of type DOMString

This attribute specifies the classification system by a URI.

No exceptions.

4.5.6.2.2 Example in Javascript

targetAudience = image.getMediaProperty(["targetAudience"]);

http://www.mpaa.org/ratings/what-each-rating-means#NC-17

http://www.mpaa.org/ratings

4.5.7 Fragments Properties

4.5.7.1 Fragment

When the MediaResource.getMediaProperty operation is invoked with "fragment" as a value of the propertyNames parameter, an object implementing the Fragment interface is returned representing the fragment property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Fragment : MediaAnnotation { attribute DOMString identifier; attribute DOMString roleLink; attribute DOMString roleLabel; };

4.5.7.1.1 Attributes

identifier of type DOMString

This attribute identifies the fragment as Media Fragment URI (temporal, spatial or track).

No exceptions.

roleLabel of typeDOMString

This attribute identifies the role of the fragment as a plain string, which can be filtered on in the getMediaProperty operation.

No exceptions.

roleLink of type DOMString

This attribute identifies the role of the fragment as a URI, which can be filtered on in the getMediaProperty operation.

No exceptions.

4.5.7.1.2 Example in Javascript

fragment = movie.getMediaProperty(["fragment"]);

http://www.example.com/video.ogv#t=10,20

4.5.7.2 NamedFragment

When the MediaResource.getMediaProperty operation is invoked with "namedFragment" as a value of the propertyNames parameter, an object implementing the NamedFragment interface is returned representing the namedFragment property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface NamedFragment : MediaAnnotation { attribute DOMString identifier; attribute DOMString label; };

4.5.7.2.1 Attributes

identifier of type DOMString

This attribute identifies a named fragment by a Media Fragment URI.

No exceptions.

label of type DOMString

This attribute contains a plain text label of a named media fragment, which can be used to contruct a Media Fragment URI fro a named fragment.

No exceptions.

4.5.7.2.2 Example in Javascript

namedFragment = movie.getMediaProperty(["namedFragment"]);

http://www.example.com/video.ogv#t=30,35

4.5.8 Technical Properties

4.5.8.1 FrameSize

When the MediaResource.getMediaProperty operation is invoked with "frameSize" as a value of the propertyNames parameter, an object implementing the FrameSize interface is returned representing the frameSize property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface FrameSize : MediaAnnotation { attribute double width; attribute double height; attribute DOMString unit; };

4.5.8.1.1 Attributes

height of type double

This attribute represents the height of the frame.

No exceptions.

unit of type DOMString

This attribute represents the unit of the frame width/height. The default value is pixels.

No exceptions.

width of type double

This attribute represents the width of the frame.

No exceptions.

4.5.8.1.2 Example in Javascript

frameSize = image.getMediaProperty(["frameSize"]);

4.5.8.2 Compression

When the MediaResource.getMediaProperty operation is invoked with "compression" as a value of the propertyNames parameter, an object implementing the Compression interface is returned representing the compression property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface FrameSize : MediaAnnotation { attribute DOMString compressionLink; attribute DOMString compressionLabel; };

4.5.8.2.1 Attributes

compressionLabel of type DOMString

This attribute specifies the compression type of the media resource as a plain string.

No exceptions.

compressionLink of type DOMString

This attribute specifies the compression type of the media resource by a URI.

No exceptions.

4.5.8.2.2 Example in Javascript

compression = video.getMediaProperty(["compression"]);

4.5.8.3 Duration

When the MediaResource.getMediaProperty operation is invoked with "duration" as a value of the propertyNames parameter, an object implementing the Duration interface is returned representing the duration property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Duration : MediaAnnotation { attribute double duration; };

4.5.8.3.1 Attributes

duration of type double

This attribute represents the duration of the media resource (in seconds) as an double value.

No exceptions.

4.5.8.3.2 Example in Javascript

duration = video.getMediaProperty(["duration"]);

4.5.8.4 Format

When the MediaResource.getMediaProperty operation is invoked with "format" as a value of the propertyNames parameter, an object implementing the Format interface is returned representing the format property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface Format : MediaAnnotation { attribute DOMString formatLink; attribute DOMString formatLabel; };

4.5.8.4.1 Attributes

formatLabel of type DOMString

This attribute specifies the MIME type of the media resource.

No exceptions.

formatLink of typeDOMString

This attribute identifies the MIME type of the media resource by a URI.

No exceptions.

4.5.8.4.2 Example in Javascript

format = image.getMediaProperty(["format"]);

http://dbpedia.org/resource/JPEG

4.5.8.5 SamplingRate

When the MediaResource.getMediaProperty operation is invoked with "samplingRate" as a value of the propertyNames parameter, an object implementing the SamplingRate interface is returned representing the samplingRate property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface SamplingRate : MediaAnnotation { attribute double samplingRate; };

4.5.8.5.1 Attributes

samplingRate of type double

This attribute specifies the audio sampling rate (in Hz) as a double.

No exceptions.

4.5.8.5.2 Example in Javascript

samplingrate = audio.getMediaProperty(["samplingRate"]);

4.5.8.6 FrameRate

When the MediaResource.getMediaProperty operation is invoked with "frameRate" as a value of the propertyNames parameter, an object implementing the FrameRate interface is returned representing the frameRate property (defined inthe Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface FrameRate : MediaAnnotation { attribute double frameRate; };

4.5.8.6.1 Attributes

frameRate of typedouble

This attribute specifies the framerate (in fps) as a double value.

No exceptions.

4.5.8.6.2 Example in Javascript

framerate = video.getMediaProperty(["frameRate"]);

4.5.8.7 AverageBitRate

When the MediaResource.getMediaProperty operation is invoked with "averageBitRate" as a value of the propertyNames parameter, an object implementing the AverageBitRate interface is returned representing the averageBitRate property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface AverageBitRate : MediaAnnotation { attribute double averageBitRate; };

4.5.8.7.1 Attributes

averageBitRate of type double

This attribute specifies the average bitrate (in kbps) as a double value.

No exceptions.

4.5.8.7.2 Example in Javascript

bitrate = video.getMediaProperty(["averageBitRate"]);

4.5.8.8 NumTracks

When the MediaResource.getMediaProperty operation is invoked with "numTracks" as a value of the propertyNames parameter, an object implementing the NumTracks interface is returned representing the numTracks property (defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

interface NumTracks : MediaAnnotation { attribute short number; attribute DOMString typeString; };

4.5.8.8.1 Attributes

number of type short

This attribute specifies the number of tracks as an integer value.

No exceptions.

typeString of type DOMString

This attribute specifies the type of the tracks that are counted as a plain string (e.g., audio, subtitle).

No exceptions.

4.5.8.8.2 Example in Javascript

numTracks = video.getMediaProperty(["numTracks"]);

4.6 MetadataSource interface

MetadataSource interface is used to identify other metadata sources.

interface MetadataSource { attribute DOMString metadataSource; attribute DOMString sourceFormat; };

4.6.1 Attributes

metadataSource of type DOMString

An URI identifying the metadata source.

No exceptions.

sourceFormat of type DOMString

The name of the actual metadata format. It should use the metadata format identifiers defined in the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY].

No exceptions.

4.6.2 Examples in Javascript

metadataSource = new MetadataSource("http://www.w3.org/2008/WebVideo/Annotations/drafts/metadata_formats/DC_example1.xml","dc");

4.7 API Status Codes

This section introduces a set of status codes for the defined API to indicate the system behavior. As described in section 4.4, the status code is returned as one of the attributes of theMediaAnnotation object returned by a method call to the API. These status codes are used on the API level, and applied to either client side or server side implementations.

Numerical Code Textual Description Example
200 OK property delivered correctly
204 No Content property retrieved without content
206 Partial Content only a subset of the available data stored in the result set
400 Bad Request syntactical error
404 Not Found the queries resource is not found
415 Unsupported Media Type get duration call on an image data store
462 Property not defined in Source Format location is not defined in MediaRSS
500 Internal Server Error internal library (e.g., extractor) crashes
562 Property not supported a subset of properties implemented

5. Usage examples

5.1 Usage as JavaScript API

This part illustrates some examples how to use this API using JavaScript in actual implementations. Moreover, in these examples it is assumed that the implementation of this API knows where to find the metadata that corresponds to a specific media resource (if necessary the location of the metadata can be configured by the use of the MetadataSource interface). The implementation should provide the mappings of different metadata formats to the core properties of the Ontology for Media Resources 1.0 specification [MEDIA-ONTOLOGY]).

Example 1: Return the name of the director of the movie "Apocalypse now".

for (var i = 0; i < mediaResourceVideoArray.length; i++) { 

titles = mediaResourceVideoArray[i].getMediaProperty(["title"], "", "", ""); 


if (noErrorStatus(titles[0].statusCode) == true) {

    for (var j = 0; j < titles.length; j++) { 

        
        if (titles[j].titleLabel == "Apocalypse Now") {
            
            
            tempResults = mediaResourceVideoArray[i].getMediaProperty(["contributor"], "", "", "");

            for (var k = 0; k < tempResults.length; k++) {
                if (tempResults[i].roleLabel == "director") {
                    result = tempResults[i];
                    break;
                }
            }  
        } 
    } 
}

}

Example 2: Retrieve the title of the second song from the album "Joshua Tree" by U2.

tracks = albumMediaResource.getMediaProperty(["fragment"], "", "", ""); trackIdentifier = tracks[1].identifier;

mediaResource = new MediaResource(); if (mediaResource.getSupportedModes() == 2 || mediaResource.getSupportedModes() == 3) { syncMediaResource = mediaResource.createMediaResource(trackIdentifier, new Array(), 2); }

title = syncMediaResource.getMediaProperty(["title"], "", "", "");

Example 3: Return the genre of the movie "Apocalypse Now".

genre = movie.getMediaProperty(["genre"], "", "", "en-us");

5.2 Usage as Web Service

This part illustrates how this API could be implemented using web services. Note that Web IDL currently does not provide bindings for web services. The given examples correspond to the examples given in Section 4.5 for each property.

The following examples illustrate how to request values for the different properties.

6. Implementation Notes

This section contains recommendations for implementators for handling missing or multiple identifiers of media resources/fragments as well as for interoperability of implementations.

6.1 Multiple identifiers of media resources or fragments

In some source formats, it could be possible to identify the resource or one of its fragments in multiple ways, e.g. by one or more identifiers, fragment name or temporal/spatial fragment URIs. For example, there could be a temporal media fragment, which can be addressed by the time range, that also has an assigned ID.

In the RDF representation of the Ontology for Media Resources, this can be represented (as recommended in the guidelines) by using owl:sameAs. To ensure a similar behaviour in the API, an implementation should return all such identifiers in a response. If queries to properties of a fragment with multiple identifiers are made, the implementation should accept each of the alternative identifiers and return the same response for each of them.

6.2 Missing fragment identifiers

There are source formats, which may contain metadata about a fragment (e.g. a track) without specifying any kind of identifier for it. For the RDF representation this is not a problem, as blank nodes can be used. In an API implementation, a client requesting the list of fragments cannot query properties of a fragment in case there is no identifier.

An implementation should generate an identifier for the fragment in such a case and should ensure that it is valid for a sufficiently long time so that the client can use it in subsequent queries to properties of fragments. The identifier is not guaranteed to remain permanently valid.

This can be implemented in different ways, including the following:

6.3 Interoperability of Implementations

The API can be implemented in two different modes. The asynchronous mode is mandatory while the synchrounous one is optional. In this context, interoperability between these modes would be a desired feature in order to provide both processing modes based on the implementation of one mode only.

An implementation of the optional synchronous mode of the API (e.g. in a Web Service) is turned into the mandatory asynchronous communication by a wrapper. Therefore the required wrapper functionality is implemented in JavaScript using the Web Workers specification [WEBWORKERS] processing non-blocking scripts. A demo of the wrapper code can be downloaded from [MAWG-REPO]. First, the existing operations of the MediaResource interface are adapted in order to support the synchronous as well as asynchronous mode (mawg_api.js). Then, the implementation of the AsyncMediaResource interface wrapping the synchronous communication is added. Therefore, the two operations of the AsyncMediaResource interface (getMediaProperty and getOriginalMetadata) refer to the corresponding synchronous calls by Web Workers (media_property_worker.js,media_property_worker.js). Finally, the result of the synchronous communication is pushed forward to the synchronous operation by invoking a callback function.

Wrapping an asynchronous implementation by an synchronous call is infeasible in JavaScript since threads cannot be suspended and interact with concurrent ones. Nonetheless, another programming language (e.g. Java), can be used to warp asynchronous API calls in web service calls.

7. Security Considerations

This specification defines a API to access metadata information related to media resources on the Web. These APIs will provide means for requesting metadata information, which can already be accessed in one or different formats, either as separate document or embedded in media resources. As such, this API introduces no additional security issue.

One should nevertheless note that some metadata could be used to access personal information about someone without declaration of agreement. For example, temporal and geographic information about a media resource could indirectly provide information about its creator.

There are related activities and technical documents in W3C working on this topics, such as Policy Requirements [POLICY-REQS] in DAP WG, ODRL 1.1 [ODRL11], P3P 1.1 [P3P11] and PLING Wiki [PLING-WIKI].

A. Web IDL description

Follow this link to download the WebIDL description as IDL file.

interface MediaResource { short getSupportedModes(); MediaResource createMediaResource(DOMString mediaResource, optional MetadataSource[] metadataSources, optional short mode); };

interface AsyncMediaResource : MediaResource { void getMediaProperty(DOMString[] propertyNames, PropertyCallback successCallback, ErrorCallback errorCallback, optional DOMString fragment, optional DOMString sourceFormat, optional DOMString language ); void getOriginalMetadata (DOMString sourceFormat, MetadataCallback successCallback, ErrorCallback errorCallback); };

interface PropertyCallback { void handleEvent (MediaAnnotation[] mediaAnnotations); };

interface MetadataCallback { void handleEvent (DOMString[] metadata); };

interface ErrorCallback { void handleEvent (DOMString errorStatus); };

interface SyncMediaResource : MediaResource { MediaAnnotation[] getMediaProperty(DOMString[] propertyNames, optional DOMString fragment, optional DOMString sourceFormat, optional DOMString language); DOMString[] getOriginalMetadata (DOMString sourceFormat); };

interface MetadataSource { attribute DOMString metadataSource; attribute DOMString sourceFormat; };

interface MediaAnnotation { attribute DOMString propertyName; attribute DOMString value; attribute DOMString language; attribute DOMString sourceFormat; attribute DOMString fragmentIdentifier; attribute DOMString mappingType; attribute short statusCode; };

interface Identifier : MediaAnnotation { attribute DOMString identifierLink; };

interface Title : MediaAnnotation { attribute DOMString titleLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

interface Language : MediaAnnotation { attribute DOMString languageLink; attribute DOMString languageLabel; };

interface Locator : MediaAnnotation { attribute DOMString locatorLink; };

interface Contributor : MediaAnnotation { attribute DOMString contributorLink; attribute DOMString contributorLabel; attribute DOMString roleLink; attribute DOMString roleLabel; };

interface Creator : MediaAnnotation { attribute DOMString creatorLink; attribute DOMString creatorLabel; attribute DOMString roleLink; attribute DOMString roleLabel; };

interface MADate : MediaAnnotation { attribute DOMString date; attribute DOMString typeLink; attribute DOMString typeLabel; };

interface Location : MediaAnnotation { attribute DOMString locationLink; attribute DOMString locationLabel; attribute double longitude; attribute double latitude; attribute double altitude; attribute DOMString coordinateSystemLabel; attribute DOMString coordinateSystemLink; };

interface Description : MediaAnnotation { attribute DOMString descriptionLabel; };

interface Keyword : MediaAnnotation { attribute DOMString keywordLink; attribute DOMString keywordLabel; };

interface Genre : MediaAnnotation { attribute DOMString genreLink; attribute DOMString genreLabel; };

interface Rating : MediaAnnotation { attribute double ratingValue; attribute DOMString ratingSystemLink; attribute DOMString ratingSystemLabel; attribute double min; attribute double max; };

interface Relation : MediaAnnotation { attribute DOMString targetLink; attribute DOMString targetLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

interface Collection : MediaAnnotation { attribute DOMString collectionLink; attribute DOMString collectionLabel; };

interface Copyright : MediaAnnotation { attribute DOMString copyrightLabel; attribute DOMString holderLink; attribute DOMString holderLabel; };

interface Policy : MediaAnnotation { attribute DOMString statementLink; attribute DOMString statementLabel; attribute DOMString typeLink; attribute DOMString typeLabel; };

interface Publisher : MediaAnnotation { attribute DOMString publisherLink; attribute DOMString publisherLabel; };

interface TargetAudience : MediaAnnotation { attribute DOMString audienceLink; attribute DOMString audienceLabel; attribute DOMString classificationSystemLink; attribute DOMString classificationSystemLabel; };

interface Fragment : MediaAnnotation { attribute DOMString identifier; attribute DOMString roleLink; attribute DOMString roleLabel; };

interface NamedFragment : MediaAnnotation { attribute DOMString identifier; attribute DOMString label; };

interface FrameSize : MediaAnnotation { attribute double width; attribute double height; attribute DOMString unit; };

interface Compression : MediaAnnotation { attribute DOMString compressionLink; attribute DOMString compressionLabel; };

interface Duration : MediaAnnotation { attribute double duration; };

interface Format : MediaAnnotation { attribute DOMString formatLink; attribute DOMString formatLabel; };

interface SamplingRate : MediaAnnotation { attribute double samplingRate; };

interface FrameRate : MediaAnnotation { attribute double frameRate; };

interface AverageBitRate : MediaAnnotation { attribute double averageBitRate; };

interface NumTracks : MediaAnnotation { attribute short number; attribute DOMString typeString; };

B. Acknowledgements

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 (JOANNEUM RESEARCH), Tobias Bürger ((public) Invited expert), Eric Carlson (Apple, Inc.), Pierre-Antoine Champin (Université de Lyon), Ashish Chawla ((public) Invited expert), Jaime Delgado (Universitat Politècnica de Catalunya), Jean-Pierre Evain ((public) Invited expert), Martin Höffernig (JOANNEUM RESEARCH), Philip Jägenstedt (Opera Software), Ralf Klamma ((public) Invited expert), WonSuk Lee (Samsung Electronics Co., Ltd.), 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), Victor Rodríguez (Universitat Politècnica de Catalunya), Felix Sasaki (Potsdam University of Applied Sciences), David Singer (Apple, Inc.), Florian Stegmaier ((public) Invited expert), John Strassner ((public) Invited expert), Joakim Söderberg (ERICSSON), Mari Carmen Suárez-Figueroa ((public) Invited expert) Thai Wey Then (Apple, Inc.), Ruben Tous (Universitat Politècnica de Catalunya), Raphaël Troncy (EURECOM), 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.

C. References