Internet DRAFT - draft-williams-json-text-sequence
draft-williams-json-text-sequence
Network Working Group N. Williams
Internet-Draft Cryptonector
Intended status: Standards Track March 14, 2014
Expires: September 15, 2014
JavaScript Object Notation (JSON) Text Sequences
draft-williams-json-text-sequence-00
Abstract
This document describes the JSON text sequence format and associated
media type.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 15, 2014.
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Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . . 3
2. JSON Text Sequence Format . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Normative References . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction and Motivation
The JavaScript Object Notation (JSON) [RFC7159] is a very handy
serialization format. However, when serializing a large sequence of
values as an array, or a possibly indeterminate-length or never-
ending sequence of values, JSON becomes difficult to work with.
Consider a sequence of one million values, each possibly 1 kilobyte
when encoded, which would be roughly one gigabyte. If processing
such a dataset requires first parsing it entirely, then the result is
very inefficient and the processing will be limited by virtual
memory. "Online" parsers help, but they are neither widely available
or widely used, nor are they easy to use.
Ideally such datasets could be parsed and processed one element at a
time. Even if each element must be parsed in a not-online manner due
to local choice of parser, the result will usually be sufficiently
online: limited by the size of the biggest element in the sequence
rather than by the size of the sequence.
This document describes the concept and format of "JSON text
sequences", which are specifically not JSON texts themselves.
1.1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. JSON Text Sequence Format
The ABNF [RFC5234] for the JSON text sequence format is as follows:
JSON-sequence = *(JSON-text 1*(text-separator))
text-separator = %x20 / %x09 / %x0A / %x0D / %2C
JSON-text = <given by RFC7159>
Figure 1: JSON text sequence ABNF
A JSON text sequence is a sequence of JSON texts, each followed by
JSON whitespace (see the 'ws' rule in the JSON ABNF) separator.
Requirements:
o Encoders MUST emit one or more JSON whitespace separator
characters after each JSON text in a sequence. Two contiguous
separators do not denote an empty JSON text between them.
o Parsers MUST be able to parser a JSON text sequence consisting of
JSON texts which do not contain newlines (except, of course,
escaped within strings), and which are separated by either
newlines, or carriage return and newline character pairs (U+000D
U+000A).
Recommendations:
o Parsers SHOULD NOT emit outputs which do not correspond to arrays,
objects or strings until the separator is read. For example, an
input of 'truefalse' is not a valid sequence of two JSON values,
true and false! Neither is 'true0' a valid sequence of true and
zero. Some parsers might in fact accept such sequences, which
creates an ambiguity that is resolved by requiring (see above)
that encoders never omit the separator.
Options:
o Parsers MAY parse sequences where the separator is missing between
any two consecutive texts provided that no ambiguity results
(namely: when the first of the two texts is an array, an object,
or a string).
o Encoders MAY have an option for encoding JSON texts "compactly",
without using newlines in the encoding. This maximizes
interoperability with JSON text sequence parsers that utilize non-
incremental, non-online JSON text parsers.
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3. Security Considerations
All the security considerations of JSON [RFC7159] apply.
JSON text sequence parsers based on non-incremental, non-online JSON
text parsers will not be able to efficiently parser JSON texts in
which newlines appear; attempting to parse such sequences with non-
incremental, non-online JSON text parsers creates a compute resource
exhaustion vulnerability.
Parsers which accidentally parse invalid sequences like 'truefalse'
(as the same as 'true\nfalse') create a mildly dangerous ambiguity.
Encoders must never produce such sequences; parsers should not accept
them.
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4. IANA Considerations
The MIME media type for JSON text sequences is application/json-seq.
Type name: application
Subtype name: json-seq
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: binary
Security considerations: See <this document, once published>,
Section 3.
Interoperability considerations: Described herein.
Published specification: <this document, once published>.
Applications that use this media type: JSON text sequences have been
used in applications written with the jq programming language.
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5. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, March 2014.
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Author's Address
Nicolas Williams
Cryptonector, LLC
Email: nico@cryptonector.com
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