Hmm, wouldn't S-exps in the same ABNF notation be

ex = ("(" *ex ")" / *%x2a-10ffff) *%x0-20

We could write the data model corresponding to this grammar in OCaml as

type ex = List of ex list | Atom of string

If we add double-quoted strings with GW-BASIC/SQL-style quoting (and resolve the ambiguity greedily):

ex = ("(" *ex ")" / *%x2a-10ffff / %x22 *(%x22 %x22 / %x0-21 / %x23-10ffff) %x22 ) *%x0-20

This corresponds to the data model

type ex = List of ex list | String of string | Symbol of string

This still seems both simpler and more expressive than the one-line grammar you give.
Maybe I'm missing a subtlety of S-expressions here, and I haven't tried it, but I think this correctly parses your examples like

(first-name"John"last-name"Smith"is-alive true age 27
address(street-address "21 2nd Street"
city"New York"state"NY"postal-code"10021-3100")
phone-numbers((type "office"number"212 555-1234")
(type "home"number"646 555-4567"))
children()spouse())

or

(
:first-name "John"
:last-name "Smith" ...
)

though of course the name-value pairing is lost there (because S-expressions lack it).

(By the way, if you want to attribute your JSON example for copyright reasons, you need to attribute it to its author or authors, not to the Wikipedia, which is just the site they posted it on.)

— ⁂ —

Maybe more importantly, though, I think your abbreviated Jevko grammar is wrong in an important way, though it describes the same set of strings as the full grammar. According to the abbreviated grammar, the Jevko examples lack most of the structure of the XML, JSON, and S-expression versions. It implies that a Jevko is an ordered sequence of (Unicode!) characters and nested Jevkos (indicated by []). We could express this data model as

type jevko = atom list
and atom = Char of char | Nest of jevko

If so, then abbreviating your S-expression example

(first-name "John" last-name "Smith")

the closest Jevko equivalent is not, as you claim

first name [John]
last name [Smith]

but rather (supposing the hyphens were just an unfortunate concession to S-expression syntax rather than actually desired)

[first name][John][last name][Smith]

We had to sacrifice the formatting white space because there's nowhere that Jevko (as specified above!) ignores it.

Using this grammar, the S-expression equivalent of the Jevko

first name [John]

is rather

("f" "i" "r" "s" "t" " " "n" "a" "m" "e" " " ("J" "o" "h" "n"))

If we instead use the full Jevko grammar

Jevko = *Subjevko Suffix
Subjevko = Prefix "[" Jevko "]"
Prefix = Text
Suffix = Text
Text = *Symbol
Symbol = Digraph / Character
Digraph = "`" ("`" / "[" / "]")
Character = %x0-5a / %x5c / %x5e-5f / %x61-10ffff

or, I think, equivalently in this context:

Jevko = *Subjevko Text
Subjevko = Text "[" Jevko "]"
Text = *(Digraph / Character)
Digraph = "`" ("`" / "[" / "]")
Character = %x0-5a / %x5c / %x5e-5f / %x61-10ffff

then we do preserve the name-value structure you seem to be going for, which your above one-line version loses. And this allows us to write

first name[John]last name[Smith]

as in your compactness examples.

I think this is a more useful level of abstraction, and it's more or less the level used by, for example, queryjevko.js's jevkoToJs, although that erroneously uses () instead of []. (Also, contrary to your assertion above that this is an example of "leaving [Jevko's data model] as-is", it forgets the order of the name-value pairs as well as I guess all but one of any duplicate set of fields with the same name and also the possibility that there could be both fields and a body.)

Essentially at this level of structure a Jevko is a (possibly empty) set of name-value pairs followed by a plaintext body ("Suffix"). This is exactly like an email message, except that the values are themselves Jevkos. In OCaml we could write:

type jevko = Jevko of (string * jevko) list * string

For your example

include[author]fields[articles[[title][body]]people[[name]]]

this gives the representation

Jevko
([("include", Jevko ([], "author"));
("fields",
Jevko
([("articles",
Jevko ([("", Jevko ([], "title")); ("", Jevko ([], "body"))], ""));
("people", Jevko ([("", Jevko ([], "name"))], ""))],
""))],
"")

although I notice that queryjevko handles it very differently.

— ⁂ —

Unlike the data model implied by your one-line grammar, I think this is an extremely useful data model. Email messages are the one and only structured data format that has remained compatible in active use and extension for over half a century; you can literally take internet email messages from 01972 and load them into a mail client today (most easily by putting them into a qmail-style maildir) and everything will just work. This is largely a result of the decentralized extensibility properties of name-value pairs: mail clients just ignore header names they don't understand, and they don't require header names that weren't originally present. This is also the basis of the extensibility of HTTP/1.0 and HTTP/1.1.

It's also very similar to the data model of popular "semistructured" or "free-form" databases of the 01990s like askSam and Filemaker. Unlike RFC-822 and HTTP/1, but like Jevko, those systems support recursively nested data. askSam even used almost the same firstname[John] syntax.

This data model does have a semantic mismatch with things like the rose-tree representation you describe at https://xtao.org/blog/rose.html, since it associates the rose-tree label with the first branch and the empty-string label with subsequent branches.

If your audience is people like me, I think it would probably be worthwhile for you to spend some time up front describing the intended semantics of a data model, as I've attempted above, rather than leaving people to infer it from the grammar. (Maybe OCaml is not a good way to explain it, though.) You might also want to specify that leading and trailing whitespace in prefixes is not significant, though it is in the suffix ("body"); this would enable people to format their name-value pairs readably without corrupting the data. As far as I can tell, this addendum wouldn't interfere with any of your existing uses for Jevko, though in some cases it would simplify their implementations.

______

Runnable OCaml code:

type jevko = Jevko of (string * jevko) list * string

(* XXX doesn't escape `[ `] `` *)
let rec dump (Jevko(hdrs, body)) = hdr(hdrs) ^ body
and hdr = function [] -> "" | (k, v) :: t -> k ^ "[" ^ dump(v) ^ "]" ^ hdr(t)

let dict kvs = Jevko(kvs, "")
let text s = Jevko ([], s)

let v = dict ["include", text "author";
"fields", dict [
"articles", dict ["", text "title"; "", text "body"];
"people", dict ["", text "name"]
]]
;;

print_endline(dump v)