JSON Entity Layout Objects


JSON Entity Layout Objects is a JSON structure for representing 1/ELF layouts.

See also: 5/YES


Copyright (c) 2016 Yurii Rashkovskii

This Specification is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This Specification is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, see http://www.gnu.org/licenses.


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 RFC 2119.

0. Goals

To provide a concise, human-readable, machine-parseable universal representation of layouts to be understood and re-used across projects.

This specification is aiming compatibility with ECMA 404

1. Layout Format

JSON representation of a layout MUST consist of a single-property object definition. The key is layout fingerprint (binary) and the value MUST be a list that:

  • MUST have its first element as a layout name
  • MAY contain one or more property entries

A property entry is a single-property object with the property name as a key and its type's fingerprint as a value. The fingerprint MUST be either a string, or a hexadecimal representation (0x...). It is RECOMMENDED to only use the hexadecimal representation for fingerprints that are not human-readable.

For example, a NameChanged layout from 3/CEP can be represented as:

  "fKib4x0LmQsjx+LwtY99+jBZMqM=": [
      "name": "String"
      "reference": "UUID"
      "timestamp": "<rfc.eventsourcing.com/spec:6/HLC/#Timestamp fingerprint>"

The order of property entries is unimportant as lexicographical sorting for the purpose of hashing is done transparently to the user.

2. Entity Format

Entity is a layout instance associated with a UUID. This UUID is not represented by any layout individual property. Following the lexicographical order of properties of the layout, an individual entity MUST be serialized as a single-property object where the key is entity's UUID and the value MUST be a list that:

  • MUST have its first element as a binary layout fingerprint
  • MUST contain the same number of property values as the number of property entries in the layout, in the same order

For example, an instance of a NameChanged entity from 3/CEP can be represented as:

  "4782a2cc-365f-4ec5-9ba4-4523744ffc1f": [
    "John Doe",

Multiple entities MAY be combined into a multiple-properties object when the order of these entities is not significant.

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