json N. Williams
Internet-Draft Cryptonector
Intended status: Standards Track April 28, 2014
Expires: October 30, 2014
JavaScript Object Notation (JSON) Text Sequences
draft-ietf-json-text-sequence-00
Abstract
This document describes the JSON text sequence format and associated
media type.
Status of this Memo
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This Internet-Draft will expire on October 30, 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" (a.k.a., "streaming") 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 but are
composed of JSON texts.
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*(ws))
ws = %x20 / %x09 / %x0A / %x0D
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 JSON text sequence encoders MUST emit one or more JSON whitespace
separator characters immediately after any JSON text.
o JSON text sequence parsers MUST NOT interpret any sequence of two
or more contiguous whitespace as a sequence of empty JSON texts.
Two contiguous separators do not denote an empty JSON text between
them as there is no such thing as an empty JSON text.
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 existing JSON parsers that might be used to construct
sequence parsers might in fact accept such sequences, erroneous
parsing when of sequences of two or more numbers. E.g., a sequence
of two numbers, 4 and 2, encoded without the required whitespace
between them would parse incorrectly as the number 42. This
ambiguity is resolved by requiring that encoders never omit the
separator.
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3. Security Considerations
All the security considerations of JSON [RFC7159] apply.
There is no end of sequence indicator. This means that "end of
file", "end of transmission", and so on, can be indistinguishable
form a logical end of sequence. Applications where this matters
should denote end of sequence by convention (e.g., Content-Length in
HTTP).
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.
The first requirement given in Section 2 (otherwise-ambiguous JSON
texts must be separated by whitespace) is critical and must be
adhered to. It is best to always emit a whitespace separator after
every JSON text emitted.
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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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