DATR¶
A declarative node–path–value equation language for compact lexical knowledge bases with default inheritance, override, path extension, and query evaluation.
Core Idea¶
DATR is a declarative language for lexical knowledge representation. A theory consists chiefly of equations associating a named node and an attribute path with a value or with another node–path description. More specific path equations override inherited general ones, enabling compact nonmonotonic default inheritance.
Evaluation answers a query such as a node at a path by selecting the most specific applicable definition, extending paths where required, and recursively resolving local or global inheritance. The language deliberately remains small while representing morphology, phonology, syntax, lexical rules, ambiguity, and reusable paradigms.
Scope of Application¶
DATR has represented inflectional paradigms, lexical entries, phonological alternations, morphological rules, typed feature-like structures, finite-state transductions, and nonlinguistic inheritance networks. Its compactness is strongest where many entries share defaults but retain structured exceptions. It has also been integrated as a lexical component for feature-based grammar environments.
Cycles, undefined paths, implementation-specific quoting, and external interfaces require explicit handling. Use today is specialist and historical, but the abstraction remains a clear design point in knowledge representation.
Clarity¶
Provide the DATR version or reference specification, exact equations, query node/path, and expected value. Distinguish local from global inheritance and literal from evaluable descriptions. Explain which shorter path licenses extension and why a more specific definition overrides a default.
Manages Complexity¶
DATR factors repeated lexical information into inheritance nodes while preserving exceptions close to the affected path. A small evaluator computes the effective entry rather than materializing all inherited facts. Path extension provides structured reuse finer than whole-record inheritance.
Abstract Reasoning¶
- Identify the node and query path.
- Find the longest prefix with an applicable equation.
- Retain any remaining path suffix for extension.
- Resolve local or global inheritance under its context rule.
- Recursively evaluate the resulting descriptor.
- Apply the suffix and assemble the value.
- Detect undefined or cyclic evaluation.
- Verify that overrides affect only their intended paths.
- Compare implementations against the reference semantics.
Knowledge Transfer¶
The portable pattern is inherit defaults at path granularity, then compute the effective value by the most specific applicable equation. It transfers to prototype systems, configuration inheritance, cascading styles, lexical paradigms, and sparse exception tables. The proposed immediate parent is Inheritance.
Relationships to Other Abstractions¶
Current abstraction DATR Domain-specific
Parents (1) — more general patterns this builds on
-
DATR is a kind of Inheritance Prime
Inheritance is the proposed immediate parent.
Hierarchy path (1) — routes to 1 parentless root
- DATR → Inheritance → Dependency
Neighborhood in Abstraction Space¶
DATR sits in a sparse region of the domain-specific corpus (81st percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.
Family — Automata, Model Checking & Formal Semantics (10 abstractions)
Nearest neighbors
- Relational Model — 0.82
- Abstract Syntax Tree — 0.82
- Formal Theory — 0.82
- Negation as Failure — 0.81
- Trie — 0.81
Computed from structural-signature embeddings · 2026-09-08