[Jsonpath] Re: Is the grammar in RFC9535 designed for PEG (Parsing Expression Grammar)

[Carsten Bormann <[e-mail]>]

On 2026-02-22, at 17:39, Alan Painter <[e-mail]> wrote:
> 
> I haven't been able to find a confirmation of this affirmation, that the rules were designed for PEG as opposed to, say, CFG (Context-free Grammar) parsers. 

The ABNF was indeed designed to be useful in a PEG context.
(It also is useful in a CFG context, but might require resolving conflicts to obtain a deterministic parse tree.)

See

https://github.com/cabo/jpt/blob/main/lib/parser/jptgrammar.abnftt

for an example of code derived from the ABNF (the abnftt tool extracts the annotations and generates the semantics for a PEG parser from those together with the PEG grammar from the ABNF; it also spits out unannotated ABNF for use in/comparison with the ABNF in the specification).

> Any pointers to a confirmation of this?

I’m sure that also was discussed on the mailing list; see

<https://mailarchive.ietf.org/arch/msg/jsonpath/h2AX9gb74ZLlPofF3DGP4YrEPL4>

for an early specimen.

But I can imagine there is no consensus document that states this as an objective; the first sentence of the Notes in the errata is just a statement of fact from someone who was there.

Grüße, Carsten