OVERVIEW OF B-XML/BML DRAFT SPECIFICATION DEVELOPED BY ARIB

Overview of B-XML/BML draft specification developed by ARIB

October 1999

Association of Radio Industiries and Bisinesses (ARIB)

1 Background

Japan will start BS digital broadcasting from December, 2000 and digital terrestrial broadcasting not later than 2003.
Due to data broadcasting digital broadcasting services are very different from existing analogue TV services. Therefore data broadcasting is expected to stimulate motivations for new business.
TV broadcasters and sound broadcasters of BS digital broadcasting can provide their data broadcasting services using their allocated bandwidth. In addition, data broadcasters who provides data services dedicatedly will be authorized this winter.
Under these circumstances, the XML WG of ARIB is currently developing an XML based multimedia content format which can be commonly used for data broadcasting services of BS and terrestrial broadcasting, based on the following objectives:

- it satisfies the requirements for digital broadcasting and its data broadcasting which have been discussed in the Digital Broadcasting System Committee of the Telecommunications Technology Council.

- it ensures high extensibility which is a feature of the XML based coding scheme and international exchangeability.

- it can also be introduced with the minimum influence on receiver costs from the start of BS digital broadcasting in the year 2000.

The first phase of this standardization which is aiming at the start of BS digital broadcasting will be finalized this October. The second phase of which scope is under consideration will be finalized in March, 2000.

2 Scheme of the draft specification

2.1 B-XML and BML

An XML application language defined in this specification consists of a set of tags for multimedia content format. The application language is called BML (Broadcast Markup Language). The scope is the same as that which has been drawn up with the basis of the formerly existing ARIB’s requirements for multimedia services and that which is currently drawn up as a presentation engine by ATSC/DASE.
The XML tags defined in each application should be provided by the DTD of its application respectively and transformed to the BML tags by XSLT for the presentation process of the receiver terminal. The XML scheme defined with this method is called B-XML(Broadcast XML).
Figure 1 illustrates the relationship between BML and B-XML. It shows that B-XML must be an extended scheme of BML in order to process any DTDs. At the presentation, the B-XML documents serve as BML documents.

Figure 1

BML (XML based multimedia application language) and
XML-like application using B-XML scheme

XSL is a style sheet language which specifies the presentation method of the XML document. This specification assumes that any XML documents are transformed into BML documents with tag-sets of multimedia content format by XSLT.
With regard to a practical example for basic services, BML is assumed to be used exclusively.

2.2 Scope of XML based coding scheme

Figure 2 depicts protocol stacks of data broadcasting(extraction of the main part)and placement of the draft specification.

Figure 2

Protocol stacks of data broadcasting (extraction) and
placement of this draft specification

Multimedia services which are described using the XML based coding scheme consist of monomedia representation data, such as bitmap, audio, character and graphics, and multimedia representation data which integrate and control the monomedia data. Multimedia documents are described with the format using BML or B-XML. In the case of broadcasting, the contents should be transmitted according to the DSM-CC carousel or the additionally specified transmission scheme by the future extension. Also, it is assumed that the contents may also be provided from the interaction path when they are additional services for broadcasting. Telecommunication control via interaction path is assumed to serve not only the acquisition of the contents but also simple transmission control for sending order and questionnaire from receiver to the computer center.

2.3 Overview of the specification

As shown in table 1, the draft specification developed by ARIB is highly consistent with that of ATSC/DASE.

Table 1

Overview of the draft specification

		Specification
Application description format		Not fixed. To be considered with JAVA and so on in the future(e.g. phase 2).
Contents	Base format	XHTML1.0
	Procedure description language	ECMAScript DOM1/2(partly)
	Presentation control	CSS1/2
	Extensions for broadcasting use	Synchronization with progress of broadcast program Automatic update of presented information Control of video and audio Operational control via remote controller Communication control for interaction path
	Application dependent contents description	XML

3 Summary of the BML extensions for broadcast use

3.1 Additional elements and attributes

The following specifications being developed by ARIB take into account the compatibility and consistencies with ATSC/DASE specifications.

3.1.1 Addition to the XHTML extension module

1) Elements and attributes for broadcast event handling

A message sent from the broadcasting station should be informed with the basis of its designated timing (spontaneous trigger, trigger by absolute time, relative time trigger within program and normal play time).
A previous notice of program end or a program end message
End message of a data program unit(smaller than the program)
Message to notify update of the broadcast information
Message to notify completion of caching the designated data
Message to notify arrival of the designated absolute time or the time set by timer
Message to notify start and end of decoding video and audio signal

2) Extensions for monomedia presentation(attributes of object element)

Attribute to keep the presentation of the specified object between two documents
Playback control for video, audio and animation, such as control of playback position, status, speed, etc.
Relation with indices within a program(Control information for random access viewing of video and audio)

3) Special effect can be set when a transition between two documents occurrs (attribute of anchor element).

4) Menu screens which is designed for the use of remote controller operation (both bitmaps and characters can be used for each element).

3.1.2 Addition to the CSS

1) Color space

· YCbCr + α(half transparent) Color space

· Addition of designation of index-color

2) Remote controller operation

· Focus shift control with the operation of the keys such as "up", "down", "left", "right" and "select". (liaison with ATSC/DASE)

3.1.3 Group of ECMAScript functions

· Reservation of a program or serial programs

· Write, read and management of NVRAM

· Telecommunication control for interaction path

· Registration of DRCS (Dynamically Re-definable Character Sets: since the fonts of the characters which are rarely used are not located in the receivers, they should be downloaded for the document where they used.)

etc.