ISO/IEC 21320-1:2015

INTERNATIONAL ISO/IEC
STANDARD 21320-1
First edition
2015-10-15
Information technology — Document
Container File —
Part 1:
Core
Technologies de l’information — Fichier conteneur de document —
Partie 1: Données de base
Reference number
©
ISO/IEC 2015
© ISO/IEC 2015, Published in Switzerland
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ii © ISO/IEC 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
5 Profile of Appnote . 2
5.1 General . 2
5.2 Annotations to Appnote . 2
Annex A (informative) Informal summary . 4
Annex B (informative) Filenames and interoperability . 5
Bibliography . 8
© ISO/IEC 2015 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information.
The committee responsible for this document is ISO/IEC JTC 1, Information technology, Subcommittee
SC 34, Document description and processing languages.
ISO/IEC 21320 consists of the following parts, under the general title Information technology —
Document Container File:
— Part 1: Core
iv © ISO/IEC 2015 – All rights reserved

Introduction
It is often useful to combine multiple digital resources into a single digital resource to make them easier
to store and process. The combined digital resource may also use data compression to minimize the
space needed for storage.
This part of ISO/IEC 21320 specifies a format for this purpose. The format is a compatible profile of that
defined by the Zip Application Note of PKWARE® Inc.
The use of Zip-based archive files for digital documents is increasingly common. Within ISO/IEC
JTC 1, there are the examples of ISO/IEC 26300 series and ISO/IEC 29500. Outside of the International
Standardization system, there are similar uses such as those of the EPUB Open Container Format (from
the IDPF) and Widget Packaging and XML Configuration (from the W3C).
The technology defined by the Zip Application Note has been in wide use in ICT industries for over
twenty years, and the specification has been freely available for much of that time. However, it has never
been formally standardized and this lack of standardization presents several challenges to standards
(including ISO/IEC Standards) that wish to reference it, including the following:
— stability of reference: what is the correct reference to give for the Zip Application Note and how can
it be ensured that this reference remains available?;
— intellectual property rights: what, if any, patents are necessary to implement this technology, and is
there a subset that may be freely implemented?;
— cultural and linguistic adaptability: is the Zip Application Note sufficient by itself, or is additional
expository material needed to define best practices for global use, e.g. the use of IRIs for file names?;
— interoperability within domain: is there a technology subset that will provide greater
interoperability within the domain of Document Container Files than permitting all features of the
Zip Application Note?.
© ISO/IEC 2015 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 21320-1:2015(E)
Information technology — Document Container File —
Part 1:
Core
1 Scope
This part of ISO/IEC 21320 specifies the core requirements for
— document container files, and
— implementations that produce and/or consume document container files.
This part of ISO/IEC 21320 normatively references the Zip File Format Specification version 6.3.3 of
PKWARE® Inc. Document container files are conforming Zip files as specified by that document.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NOTE Each of the following documents has a unique identifier that is used to cite the document in the text.
The unique identifier consists of the part of the reference up to the first comma.
ISO/IEC 10646:2014, Information technology — Universal Coded Character Set (UCS)
1)
Appnote, APPNOTE.TX — ZIP File Format Specification, PKWARE® Inc., September 2012
2)
IETF RFC 1951, DEFLATE Compressed Data Format Specification version 1.3, May 1996
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
byte
sequence of 8 bits
3.2
digital resource
sequence of bytes (3.1)
3.3
document container file
digital resource that conforms to this part of ISO/IEC 21320
3.4
implementation
processor that operates on document container files (3.3)
1) Available at http://www.pkware.com/documents/APPNOTE/APPNOTE-6.3.3.TXT
2) Available at http://www.ietf.org/rfc/rfc1951.txt
© ISO/IEC 2015 – All rights reserved 1

4 Requirements
A digital resource is conformant to this part of ISO/IEC 21320 when it is in accord with the provisions of
this part of ISO/IEC 21320. Such a digital resource is a document container file.
An implementation is conformant to this part of ISO/IEC 21320 when it processes conformant digital
resources in accord with the provisions of this part of ISO/IEC 21320.
5 Profile of Appnote
5.1 General
The provisions of this part of ISO/IEC 21320 are the provisions of Appnote as modified by the
annotations provided in Table 1.
The provisions of Appnote shall be determined by interpreting Appnote in its own terms, and according
to its own context.
EXAMPLE Appnote’s Clause 3 has its own “Notations” which differ from those used by ISO and IEC. Appnote’s
own notations apply for the purposes of its interpretation. So, for instance, “must” in the Appnote is to be read as
equivalent to “shall” in ISO and IEC Standards.
5.2 Annotations to Appnote
Table 1 is a two-column table which provides annotations to Appnote. The left-hand column of Table 1
contains section numbers of Appnote, and text in parentheses, which together identify a portion
of Appnote. The right-hand column of Table 1 gives an annotation to the sections so identified. Each
annotation applies to the corresponding identified section of Appnote.
NOTE The annotations to Appnote can have an effect beyond the section of the Appnote to which they
explicitly apply. For example, if a specific technical feature is prohibited by an annotation, no other mention of
that feature can be interpreted as re-admitting that feature to this part of ISO/IEC 21320.
Table 1 — Annotations to Appnote
Appnote section Annotation
4.3.3 (general Format of a Zip file) Resources conforming to this part of ISO/IEC 21320 shall not span
multiple volumes, and shall not be split into user-defined segment
sizes.
4.3.6 (overall Zip file format) Resources conforming to this part of ISO/IEC 21320 shall not
contain either “encryption header” or “archive decryption header”
constructs.
4.3.8 (file data) Files contained in archives shall not be encrypted using the mecha-
nisms described in Appnote.
4.3.9.6 (data descriptor) The “central directory encryption method” mentioned by this sub-
clause of Appnote shall not be used.
NOTE 1 Although the above provision for Appnote,4.4.3 permits values for “version needed to extract” which imply
support for features of value 1.1 (“File is a volume label”), 2.0 (“File is a folder […]” etc.), 2.1 (“File is compressed using
Deflate64™”), 2.5 (“File is compressed using PKWARE DCL Implode”) and 2.7 (“File is a patch data set”), none of these
features are permitted by this part of ISO/IEC 21320.
NOTE 2 To promote global use, implementers are strongly encouraged to support bit 11 of the “general purpose bit flag”
(Appnote, 4.4.4) being set.
NOTE 3 For file names, any Unicode character is allowed. However, different file systems impose different restrictions on
permissible characters, and RFC 3987 introduces its own restrictions. As a result, it might not be possible to create a file
name or IRI from a zip item name.
NOTE 4 Some file systems perform Unicode normalization or case normalization of file names while others do not. Thus,
multiple different zip item names in a single Zip archive may become identical after normalization.
2 © ISO/IEC 2015 – All rights reserved

Table 1 (continued)
Appnote section Annotation
4.3.10 (archive decryption header) The “archive decryption header” feature specified by this subclause
of Appnote shall not be used.
4.3.13 (digital signature) The “digital signature” feature specified by this subclause of
Appnote shall not be used.
4.4.1.5 (explanation of fields) Archives shall not be split or spanned.
4.4.3 (version needed to extract) Resources conforming to this part of ISO/IEC 21320 shall not con-
tain a “version needed to extract” value greater than 45.
The ZIP64™ extension feature version 1 may be used.
The ZIP64™ extension feature version 2 shall not be used.
4.4.4 (general purpose bit flag) Bit 0, bits 4 to 10 and 12 to 15, shall not be set.
Bit 11 should be set. If the value of any byte in the file name or file
comment is greater than 0x7F, bit 11 shall be set.
If bit 11 is set, the file names and comment fields for the document
container file shall be Unicode strings encoded using the UTF-8
encoding scheme as specified in ISO/IEC 10646:2014, Annex D.
4.4.5 (compression method) The compression method shall be either 0 (“stored”) or 8
(“deflated”).
4.7 (manifest files) This clause of Appnote shall be disregarded.
5.5 (deflating) Files compressed using this method shall use the mechanisms speci-
fied in IETF RFC 1951.
6.0 (traditional PKWARE encryption) This clause of Appnote shall be disregarded.
7.0 (strong encryption specification) This clause of Appnote shall be disregarded.
8.0 (splittin
...