In the field of digital and interactive television, Nested Context Language (NCL) is a declarative authoring language for

hypermedia Hypermedia, an extension of the term hypertext, is a nonlinear medium of information that includes graphics, audio, video, plain text and hyperlinks. This designation contrasts with the broader term ''multimedia'', which may include non-interac ...

documents. NCL documents do not contain multimedia elements such as audio or video content; rather they function as a "glue" language that specifies how multimedia components are related. In particular, NCL documents specify how these components are synchronized relative to each other and how the components are composed together into a unified document. Among its main facilities, it treats hypermedia relations as first-class entities through the definition of hypermedia connectors, and it can specify arbitrary semantics for a hypermedia composition using the concept of composite templates. NCL is an

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...

application language that is an extension of

XHTML Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages. It mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated. While HTML, prior ...

, with XML elements and attributes specified by a modular approach. NCL modules can be added to standard web languages, such as

XLink XML Linking Language, or XLink, is an XML markup language and W3C specification that provides methods for creating internal and external links within XML documents, and associating metadata with those links. The XLink specification XLink 1.1 is a ...

and SMIL. NCL was initially designed for the Web environment, but a major application of NCL is use as the declarative language of the Japanese-Brazilian

ISDB-Tb ISDB-T International, or SBTVD, short for Sistema Brasileiro de Televisão Digital ( en, Brazilian Digital Television System), is a technical standard for digital television broadcast used in Brazil, Argentina, Peru, Botswana, Chile, Honduras, Ve ...

(International Standard for Digital Broadcasting) terrestrial DTV

digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advanc ...

middleware Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement co ...

(named Ginga). It is also the first standardized technology of the

ITU-T The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...

multimedia application framework series of specifications for

IPTV Internet Protocol television (IPTV) is the delivery of television content over Internet Protocol (IP) networks. This is in contrast to delivery through traditional terrestrial, satellite, and cable television formats. Unlike downloaded media, ...

(internet protocol television) services. In both cases it is used to develop interactive applications to digital television.

Structure of an NCL document

NCL was designed to be modular to allow for use of subsets of modules according to the needs of the particular application. The 3.1 version of the standard is split into 14 areas with each module assigned to an area. Each module in turn defines one or more XML elements. The areas and associated modules are *Structure **Structure Module *Components **Media Module **Context Module *Interfaces **MediaContentAnchor Module **CompositeNodeInterface Module **PropertyAnchor Module **SwitchInterface Module *Layout **Layout Module *Presentation Specification **Descriptor Module *Timing **Timing Module *Transition Effects **TransitionBase Module **Transition Module *Navigational Key **KeyNavigation Module *Presentation Control **TestRule Module **TestRuleUse Module **ContentControl Module **DescriptorControl Module *Linking **Linking Module *Connectors **ConnectorCommonPart Module **ConnectorAssessmentExpression Module **ConnectorCausalExpression Module **CausalConnector Module **CausalConnectorFunctionality Module **ConnectorBase Module *Animation **Animation Module *Reuse **Import Module **EntityReuse Module **ExtendedEntityReuse Module *Meta-Information **Metainformation Module

NCL profiles

Profiles are standard subsets of modules. Profiles defined by the standard include * Full profile – includes all NCL Modules * Enhanced Digital TV profile (EDTV) – includes the Structure, Layout, Media, Context, MediaContentAnchor, CompositeNodeInterface, PropertyAnchor, SwitchInterface, Descriptor, Linking, CausalConnectorFunctionality, ConnectorBase, TestRule, TestRuleUse, ContentControl, DescriptorControl, Timing, Import, EntityReuse, ExtendedEntityReuse, KeyNavigation, Animation, TransitionBase, Transition and Metainformation modules * NCL Basic Digital TV profile (BDTV) – includes the Enhanced Digital TV profiles except for the Animation, TransitionBase and Transition modules

Authoring tools

Tools for creating interactive DTV application in NCL include: *

NCL Eclipse NCL Eclipse is a plugin for Eclipse IDE to assist in the development of Nested Context Language (NCL) applications. NCL is the standard declarative language for ISDB-Tb (International System for Digital Broadcast Terrestrial Brazilian) and also i ...

* NCL Composer.

References

External links

NCL Official Web Site

NCL Handbook

Telemidia Lab

NCL Resources
a number of resources supporting NCL.

NCL players

GINGA-NCL Reference Implementation
available under GPLv2 (in Portuguese).
GHTV GINGA-NCL player
for Windows and Linux under

Creative Commons Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has release ...

Attribution-NonCommercial-NoDerivs 3.0 License (in Portuguese).
WebNCL Player
Web-based, available under GPL. Markup languages XML-based standards Technical communication Computer file formats Broadcast engineering Digital television ISDB