Lingua PSA: A Machine-Verified Constructed Language for Everyday Use

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Lingua PSA is a constructed language designed for everyday use, including conversation, work, commerce, family, and the internet. Its architecture is machine-verified: phonotactics, lexical admission, derivational morphology, an Extended Backus-Naur Form (EBNF) grammar, and a constraint layer are governed by an executable validator, and a sentence is considered grammatical only when accepted by the parser. This paper presents the self-contained learning artifact for release v12.4, culminating an evolutionary program that began with the v1.2 core specification. Version 1.3 introduced nominal composition through the linker o, manner adverbs in -mo, and discourse connectors. Version 2.0 added correlatives, an analytic passive formed with -da and the agent preposition de, and a technical register. The subsequent development program, spanning v2.1 through v12.0, expanded the language to 767 registered items, 13 derivational suffixes, and 4,816 computable derived words. Four successive verification rounds strengthened the system: the v12.1 external audit, addressing reproducibility, negative-test integrity, and taxonomic consistency; the v12.2 meta-audit, testing the validator itself through malformed-input probes, mutation fuzzing, independent numerical recounts, and production-by-production EBNF/parser cross-checks; the v12.3 graded verification round, which evaluated the complete test battery against a twelve-point rubric; and the v12.4 property-verification round, which introduced an EBNF-based sentence generator producing 4,000 sentences that the parser must accept. Across these rounds, the audits identified and corrected defects involving tokenization, interrogative licensing, punctuation, rejection attribution, embedded questions, free relatives, courtesy particles, coordination, existential clauses, exclamatives, recursive nesting, malformed inputs, and constraint-checking boundaries. The resulting test battery contains 641 positive sentences, all successfully parsed, and 233 negative sentences, each rejected by its designated rule, with zero validator errors. The admission gate also rejected forty-four Academy proposals during the development cycle on phonotactic and phonemic grounds; each was subsequently reformulated to satisfy the formal constraints. All numerical results reported in this paper are generated directly from the validator's own output. “Future generations must improve the orthography, morphology, and practical use of Lingua PSA, for heresy is what prevents the improvement and refinement of the language.” — Founding Pledge, normative since v1.0