MeridianMERIDIAN

S-Expression

container.object.s_expression

Balanced nested parenthetical serialization — the S-expression family: Lisp/Scheme source, linguistic constituency/dependency parse trees (Penn Treebank, OntoNotes: "(ROOT (S (NP (NN cat)) (VP (VBZ sits))))"), and code ASTs ("(program (call (id print) (string hi)))"). A nested structure of the form (head child child ...), distinguished from a comma/whitespace list by its balanced, recursively-nested parentheses.

Domain
container
Category
object
Casts to
VARCHAR
Scope
Universal
Frictionless
string

Shape

Length at least 5 characters.

Pattern
^\s*\(.*\)\s*$
ValueLengthShape
(ROOT (S (NP (NN cat)) (VP (VBZ sits))))40matches
(program (call (id print) (string hello)))42matches
(+ (* 2 3) (- 4 1))19matches
(a (b c) (d (e f)))19matches
(S (INTJ (UH Uh)) (, ,) (NP-SBJ (PRP I)) (VP (VBP think)))58matches
ROOT (S (NP (NN cat)) (VP (VBZ sits))))39rejected: first character dropped

Told apart

1 of the 6 other object types accept every one of these samples on shape alone.

Detection notes

New 2026-07-05 (company-reference audit; author-approved as a general S-expression type over a narrow parse_tree leaf). Mined from 1,292 corpus columns — `trees`/`parse_tree`/`ast` — every one mislabelled container.array.comma_separated by the delimiter detector. The 244-dim model cannot predict this leaf; it is recovered at profile time by the deterministic `s_expression_recovery` Sharpen guard when >=90% of a column's values pass the balanced-nested-paren structural check (finetype_core::structure::is_s_expression). Value-based (0048), no header gate — the structural signature is self-precise (corpus over-recovery: zero). NO retrain (0096; value-determinable → Sharpen).

Use it

CLI · DuckDB
$ finetype infer -i "(ROOT (S (NP (NN cat)) (VP (VBZ sits))))" --mode column
→ container.object.s_expression

SELECT ft_infer('(ROOT (S (NP (NN cat)) (VP (VBZ sits))))');
-- → 'container.object.s_expression'
Cast expression
CAST({col} AS VARCHAR)

Schema

https://meridian.online/schemas/container.object.s_expression — JSON Schema 2020-12, also from finetype taxonomy container.object.s_expression -o json-schema. Frictionless type string.

Aliases

sexps_exprparse_treelisp

Type Registry