Title:Standard JSON representation method
Last modified:2014-06-20 00:43:41 UTC (Fri, 20 June 2014)
Author:Raphael ‘kena’ Poss
Type:Standards Track
Source:scep0105.rst (fp:XGG0y0ufgpBGRxzHbY76hYuc8ysaVo5CF7YZv5RA73COLw)

The Structured Commons object model is defined semantically in SCEP 101 [1], independently from its particular representation in a computer system. Conversely, there may exist multiple valid representations for an object.

This SCEP defines the canonical representation of Structured Commons objects as a JSON object, with method name "json".


The json representation maps objects to a JSON object [2].

Object files are represented by JSON character strings.

Object dictionaries are represented by JSON associative arrays.

Dictionary names that map to objects are represented by associative array entries that are the JSON representation of the enclosed object.

Dictionary names that map to fingerprints are represented by a JSON list containing one string entry containing the compact representation of the fingerprint.


For example, the following Structured Commons object:

  +-- hello.txt (file)
  |   hello, world!
  +-- link (fingerprint reference)

can be represented by the following JSON text:

 "hello.txt" : "hello, world!"
 "link" : ["fp:0cYMtlAA_T4_vG2NBmtEeB7uh26b1tpzb-0qiDGHxGrIMw"]

Alternate representation

When an object file contains many occurrences of byte codes outside of the printable range, the "direct" JSON representation using Unicode escape sequences ("\uXXXX") can incur a large space overhead, up to 500% of the length of the original byte string.

For applications where binary data is common, this specification provides an alternate, mutually compatible encoding for file objects: a JSON list containing one string containing the Base64 encoding of the object (using the special URL safe alphabet defined in [3]).

With this alternate representation, the example above can be encoded as follows:

 "hello.txt" : ["aGVsbG8sIHdvcmxkIQ=="],
 "link" : ["fp:0cYMtlAA_T4_vG2NBmtEeB7uh26b1tpzb-0qiDGHxGrIMw"]

The alternate encoding is not ambiguous with fingerprint references, since the Base64 encoding of a file object can never start with the three characters "fp:".

Example/reference implementation

Example code in Python is provided separately:


[1]SCEP 101. "Structured Commons Object Model and Fingerprints". (
[2]RFC 7159. "The JavaScript Object Notation (JSON) Data Interchange Format". (
[3]RFC 4648. "The Base16, Base32, and Base64 Data Encodings". (