Part 2: Abstract transmittal format

Annex A

(informative)

Guidelines for encodings

A.1 Table of contents and introduction

This annex describes guidelines that may assist in developing encoding formats that conform to this part of ISO/IEC 18023.

 A.1.1 Table of contents

Table A.1 is the table of contents for this annex:

A.1.2 Introduction

This annex contains guidelines that may ease development efforts. Guidelines are provided for:

1. the use of encoding elements,
2. the use of compression, and
3. achieving efficiency.

Each of these topics is discussed below.

A.2 Encoding elements

An encoding element is encoding-specific and will depend on the type of encoding being developed. Encoding elements are defined in 5.2.2 Encoding element grammar.

For a character-based encoding (e.g., a clear text encoding), an encoding element is also character-based. The purposes served by an encoding element in a character-based encoding include, but are not limited to:

1. a delimiter,
2. a field separator,
3. a field name, and/or
4. whitespace.

For a binary encoding, an external element consists of a specific set of bits assigned a meaning. The purposes served by an encoding element in a binary encoding include, but are not limited to:

1. a <FIELD> (see 5.2.8 DRM objects) size specification,
2. a <FIELD> continuation indicator,
3. a <FIELD> extension indicator,
4. a reference to other elements within the transmittal, and/or
5. to provide field quantization information.

A.3 Compression

An encoding may specify how compression techniques apply. All compression should ensure that the initial uncompressed data is recreated after decompression. Thus, only lossless compression should be supported (see 4.4 Compression).

Compression may be applied in many different ways. The entire transmittal may be compressed using external compression techniques, subset of data within a transmittal may be defined for compression purposes, and/or individual <DRM OBJECTS> within the transmittal may be individually compressed.

A.4 Access efficiency

An encoding may use <ENCODING ELEMENT>s to enable more efficient access to portions of a transmittal. It should be possible to remove all <ENCODING ELEMENT>s used for access efficiency without impacting the meaning of the environmental data.

http://www.iso.ch/iso/en/ittf/PubliclyAvailableStandards/ISO_IEC_18023-2_Ed1.html