This deposit presents Structural Signature Analysis (SSA), a general framework for classifying unknown symbolic systems — undeciphered scripts, artificial languages, emergent symbolic codes, and algorithmically generated pseudo-texts — using information theory and structural analysis alone. A corpus over an unknown alphabet is characterised by a signature functional that returns scope-indexed invariants across a fixed hierarchy of layers (symbol, token, line, block, partition): block entropy, conditional predictability, count dispersion, the rank–frequency exponent, a positional-state decomposition, finite-state acceptor coverage and over-generation, positional lift, and a maximal-divergence partition. Each invariant is formalised as a named, reusable operator with a precise definition, closed form, input/output behaviour, and example; the twelve operators are presented as a catalogue. Candidate generative mechanism families induce manifolds in signature space, and a system is classified by the minimal-dimension family whose manifold realises its observed signature vector jointly. The central result is the Decoupling Principle: discrimination resides in the coupling structure of the signature functional under a mechanism family rather than in any single invariant. A family is falsified when one parameter sign-locks two signatures that the target system holds at independent values, and its successor must decouple them. This converts open questions about an unknown system into a falsifiable constraint-satisfaction problem. The framework generalises a prior structural and information-theoretic study of the Voynich Manuscript (Beinecke MS 408), reframing that work as one instance of SSA: its layered model, its statistical signatures, its transcription-sensitivity controls, and its generative null-model experiments correspond directly to the operators and principles defined here. All quantitative claims are conditioned on a declared tokenisation; promotion of a classification from structural to empirical for any given system requires evaluating the operators on that system's corpus. This is a companion to Structural Signatures of the Voynich Manuscript: A Layered Decomposition and a Generative Falsification (Carlo). It makes no claim regarding the meaning, language, or authorship of any specific system.unknown symbolic systems, undeciphered scripts, symbol sequence analysis, information theory, Shannon entropy, conditional entropy, rank-frequency distribution, Zipf's law, dispersion index, hidden Markov model, finite-state grammar, generative model, null model, model falsification, signature space, computational linguistics, quantitative linguistics, Voynich Manuscript, formal methods, classification
Matthew Carlo (Tue,) studied this question.