First Edition: February 2022. Last revised: January 2024.
Also available on GitHub.
No breaking changes. On that note, let this be stated as an official goal:
No breaking changes shall be introduced to this specification.
Copyright and license section: updated year.
See also section: rearranged, added link to extensions.
Jevko is a versatile minimal syntax for encoding tree-structured information.
It can be used to define simple and portable formats and languages in a variety of domains, such as data interchange, configuration, or text markup.
Jevko is completely programming-language independent and has no inherent semantics. It is a pure syntactic building block which can be joined together with other syntactic or semantic building blocks in a modular way.
These additional building blocks are specified separately. The purpose of this specification is only to describe the basic syntax in terms of Unicode [Unicode] code points, providing a reference for implementations as well as other specifications.
The formal grammar definitions in this document use the ABNF notation [RFC 5234].
The name Jevko /ˈd͡ʒef.kəʊ/ is derived from Polish drzewko /ˈdʐɛf.kɔ/, meaning small tree.
A valid Jevko sequence is a sequence of Unicode code points which
conforms to the Jevko rule defined in
this document.
The syntax of Jevko is extremely minimal.
There are two main grammatical rules: the Jevko rule and the Subjevko rule.
The Jevko rule is the start symbol of the
grammar.
It refers to the Subjevko rule which in turn refers back
to Jevko: the two rules are mutually-recursive.
This makes Jevko a recursive grammar.
This recursion is minimal: if a reference to either
Jevko or Subjevko was removed, the grammar
would cease to be recursive.
All remaining rules are non-recursive. Notably:
The Character rule covers
all possible code points except three.
The three remaining code points (Delimiters) are the only special
characters in the grammar.
There are no special rules for whitespace. All whitespace
characters are captured by the Character rule.
All rules are described and formally defined in the following
sections. The first section covers rules for delimiters. The remaining
sections describe the rest of the rules, top to bottom, starting with
Jevko.
Jevko is based around three delimiters, named by the Delimiter rule:
![[^youtube]](/youtube_icon.svg){kind=icon}
![[^codeberg]](/codeberg_icon.svg){kind=icon}
![[^github]](/github_icon.svg){kind=icon}
![[^mastodon]](/mastodon_icon.svg){kind=icon}
![[rss]](/rss_icon.svg){kind=icon}
![[^TAO]](/tao-logo.svg){kind=logo}
![[support-jevko]](/support_icon.svg){kind=icon}
![[^translate]](/translate_icon.svg){kind=icon}
Delimiter = Opener / Closer / EscaperThe delimiters are defined as the following code points:
Opener = %x5b ; left square bracket
Closer = %x5d ; right square bracket
Escaper = %x60 ; grave accentEquivalently:
Opener = "["
Closer = "]"
Escaper = "`"A Jevko is a sequence of zero or more
Subjevkos followed by a Suffix.
Jevko = *Subjevko SuffixA Subjevko is a Prefix followed by an
Opener, followed by a Jevko, followed by a
Closer.
Subjevko = Prefix Opener Jevko CloserEquivalently:
Subjevko = Prefix "[" Jevko "]"A Prefix is an alias for Text:
Prefix = TextThis alias identifies that the Text is a part of a
Subjevko. A Prefix is always followed
by an Opener.
A Suffix is an alias for Text:
Suffix = TextThis alias identifies that the Text is a part of
Jevko. A Suffix is never followed by
an Opener.
Text is a sequence of zero or more
Symbols:
Text = *SymbolA Symbol is either a Digraph or a
Character:
Symbol = Digraph / CharacterA Digraph is an Escaper followed by a
Delimiter:
Digraph = Escaper DelimiterEquivalently:
Digraph = "`" ("`" / "[" / "]")
Digraph = "``" / "`[" / "`]"A Character is any code point which is not a
Delimiter:
Character = %x0-5a / %x5c / %x5e-5f / %x61-10ffff[Unicode] The Unicode Consortium, “The Unicode Standard”, the latest version, http://www.unicode.org/versions/latest/.
[RFC 5234] Crocker, D., Ed. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF”, STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, https://www.rfc-editor.org/info/rfc5234.
Jevko interactive railroad diagrams, https://jevko.org/diagram.xhtml
“The Jevko Syntax: Extensions Specification”, January 2024, https://jevko.org/extensions.html
Jevko examples, https://github.com/jevko/examples
© 2022-2024 Jevko.org
This document is licensed under the MIT License:
Copyright © 2022-2024 Jevko.org
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.; start symbol, main rule #1
Jevko = *Subjevko Suffix
; main rule #2, mutually recursive with #1
Subjevko = Prefix Opener Jevko Closer
; delimiters
Delimiter = Opener / Closer / Escaper
Opener = %x5b ; left square bracket
Closer = %x5d ; right square bracket
Escaper = %x60 ; grave accent
; aliases
Suffix = Text
Prefix = Text
; text
Text = *Symbol
Symbol = Digraph / Character
Digraph = Escaper Delimiter
; Character is any code point which is not a Delimiter
Character = %x0-5a / %x5c / %x5e-5f / %x61-10ffff