With the introduction of software execution capabilities, the complexity of receivers grows. There are countless issues that need to be addressed when designing receivers. Some could be classified as transport issues, application issues, and execution environment issues. Others could be
[ATSC] Advanced Television Systems Committee (ATSC) www.atsc.org
[DASE] ATSC DTV Application Software Environment Level 1 (DASE-1) www.atsc.org/standards.html
[ETSI] European Telecommunications Standards Institute www.etsi.org
[FTP] File Transfer Protocol, RFC959, 10.1985, IETF ftp://ftp.rfc-editor.org/in-notes/rfc959.txt
[HTTP1.0] Hypertext Transfer Protocol, HTTP/1.0, RFC1945, 05.1996, IETF ftp://ftp.rfc-editor.org/in-notes/rfc1945.txt
[HTTP1.1] Hypertext Transfer Protocol, HTTP/1.1, RFC2616, 06.1999, IETF ftp://ftp.rfc-editor.org/in-notes/rfc2616.txt
[JavaTV] JavaTV API Technical Overview, Version 1.0 java.sun.com.
[JVM] Java Virtual Machine (JVM) java.sun.com
[MHP] Digital Video Broadcast (DVB) Multimedia Home Platform (MHP) www.mhp.org
[MPEG] Moving Picture Expert Group (MPEG) www.mpeg.org
[MPEG2] MPEG-2, ISO/IEC 13818 Parts 1-6 www.mpeg.org
[MPEG4] MPEG-4, ISO/IEC 14496 Parts 1-6 www.mpeg.org
[OCAP] CableLabs, Open Cable Architecture Platform (OCAP) www.cablelabs.com
[OCAP1.0] OCAP 1.0 Profile, OC-OCAP-DS-010430 www.scte.org
[OSGI] Open Services Gateway Initiative (OSGI) www.osgi.org.
[SCTE] Society of Cable Telecommunications Engineers (SCTE) www.scte.org
[SMPTE] Society of Motion Picture and Television Engineers (SMPTE) www.smpte.org
[TLS] The Transport Layer Security (TLS) Protocol version 1.0, RFC 2246, 1999, IETF . ftp://ftp.rfc-editor.org/in-notes/rfc2246.txt
[URI] Uniform Resource Identifiers (URI), RFC 2396, 8.1998, IETF ftp://ftp.rfc-editor.org/in-notes/rfc2396.txt
[UUID] SMPTE 298M, 1997: Universal Labels for Unique Identification of Digital Data www.smpte.org
Chapter 5. Declarative Content
Declarative content earned its
Document layout software vendors were developing their own document structure, format and encoding, giving rise to interpretability issues. For example, proprietary markup languages have been used by word processors to address their need to describe how each part of the document was to look. Today, in the context of iTV and the Internet, declarative content and markup content refer to the same type of content. Standardization efforts were launched to address this problem. The first widely accepted declarative content language is the Standard Generalized Markup Language (SGML), defined in ISO 8879 [SGML]. SGML
The basic building block of all documents written using markup languages is the element. It is
Each element is associated with a list of attributes, each with a name and a value assigned by the document author. Attribute value pairs appear before the final ">" of an element's start tag. As an example, one could use "<paren-name color='red'>see Figure 5</paren-name>" to
In addition to SGML, the developers of the Internet were familiar with the LISt Processing (LISP) language, used by Artificial Intelligence (AI) programmers. In LISP, the parentheses notation is commonly used to specify expressions, declarations, functions, and program blocks. On the one hand, the SGML markup notation had the advantage that the parentheses were given
To enable automation of document processing, however, some standard structure was needed. In the same way that forms enable organization to improve the efficiency of their operation, document structure enables computers to automatically process documents. As it turns out, SGML has already induced an element tree structure with a single root element. Additional constraints on the structure that enable interoperability are specified by the Document Type Definition (DTD), which
The parts of a document written in an SGML-based language are as
Typically, for the documents written in a given markup language, the first three parts are fixed. In other words, two documents in which all four parts are identical are written in the same language; the reverse, however, might not be true as it is possible that a markup language uses multiple character sets of DTDs.
SGML processors have a
Figure 5.1. A simplified conceptual architecture of an SGML document processor.