æthel

In the beginning was the word, and the word had a Type.

Source code and Python module for the representation of typelogical grammar derivations and their extraction from Lassy-style dependency graphs.

Cool things to look out for:

• an interface to Alpino outputs -- convert dependency graphs to λ-terms and annoy your informal linguist friends!
• a faithful implementation of (temporal) modal linear logic proofs and its terms -- almost as good and twice as slow as doing it on Haskell!

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Installing & Using æthel

This repository is required to access and play with the æthel dataset, which contains typelogical analyses for the majority of the Lassy Small corpus. Begin by cloning the project locally and unzipping the dump file in data/ (remember to unzip). You can then install the project by running:

python3 -m pip install .

Afterwards, you can load the dump by running:

from aethel import ProofBank

dataset = ProofBank.load_data("PATH_TO_DUMP_FILE")

Note that loading might take a short while, as proofs are reconstructed bottom up and type-checked along the way.

Example usage:

Please refer to examples/ for some hands-on guides on how to use the module.

Major Changelog

Different major versions are not backward compatible. Train/dev/test segmentation is respected to the largest extent possible. If looking for older versions, take a look at other branches of this repository.

1.0.1 (02/2023)

Tidier packaging and installation. Backwards compatible with 1.0.0x.

1.0.0a (06/2022)

Implementation of long-postponed changes to the type system. In practical terms, type assignments are a bit more complicated but all proofs are now sound wrt. to the underlying logic.

• Adjunction: diamonds and boxes are no longer treated as ad-hoc type constructors, and their adjoint nature is made explicit (i.e. ◇□A⇒A⇒□◇A). The diamond elimination and arrow introduction rules are now explicit to which variable is being abstracted or replaced.
• Bracketing Structure: brackets are now explicated to regulate the applicability of diamond eliminations and box introductions.
• Structural Rules: rules are now split between logical and structural. For the purpose of allowing extraction of hypotheses nested within unary structures, we now use an extraction modality reserved for the higher-order types that supply them. The modality is paired to a single structural rule which permits outwards movement: <Χ>!, <Γ, Δ> → <Γ, <Χ>!, Δ>
• Proofs & Terms: Due to the presence of term-neutral structural rules (and the ambiguity inherent to the implicit cut of the diamond elimination rule) proofs are now defined separately from syntactically valid terms.
• Multi-word Phrases: Multi-word phrases are heuristically fixed to the extent possible; this permits the extraction of correct proofs when (previously unstructured) constituents are elided under a conjunction. Coverage is slightly increased.

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Minor Changelog

1.0.0a5 (01/2023)

• Explicit objects are hypothesized from within the local phrase.

1.0.0a4 (12/2022)

• Past participles now have explicit objects.

1.0.0a3 (10/2022)

• Structural extraction now properly renames variables.

1.0.0a2 (10/2022)

• Diamond elimination terms now act as variable binders that explicate their position via the case [τ:term] of [x:variable] in [σ:term] term constructor (meaning "replace any occurrence of x in σ with τ").
• To ease comprehension, the left and right side occurrences of the "same" variable in diamond eliminations are no longer identified, i.e. the substitute and substituted variables have unique names.

1.0.0a1 (07/2022)

• Proofs are delivered in η-normal form, and variables are assigned unique names.
• Natural deduction is back-and-forth compatible with proof nets again.
• A few leftover proofs failing the linearity criterion are removed.

Project Structure

The package source code can be found in directory src.

• aethel.frontend is the high-level interface that allows user access to the processed corpus.
• aethel.mill contains an implementation of the grammar's type system, namely Implication-Only Multiplicative Intuitionistic Linear Logic with Unary Temporal Modalities. Each of the following modules provide implementations for specific aspects of the logic:
  • aethel.mill.proofs - classes & methods for the representation and manipulation of judgements, rules and proofs in natural deduction format.
  • aethel.mill.nets - ditto for decomposition formulas, axiom links and proof nets, and conversion to and from natural deduction.
  • aethel.mill.terms - a rudimentary implementation of the term calculus.
  • aethel.mill.types - an implementation of logical formulas.
  • aethel.mill.structures - a handy abstraction over the antecedent structure of logical judgements.
  • aethel.mill.serialization - parsers and serializers for the above.
• aethel.alpino contains utilities to interface with Alpino-style graphs
  • aethel.alpino.transformations contains the linguistic transformations necessary to make Alpino analyses amenable to proof-theoretic analyses, and packs them into a single pipeline. Warning: Not for the faint of heart.
  • aethel.alpino.extraction implements the extraction algorithm, whereby transformed Alpino graphs are gradually proven in a bottom-up fashion.
  • aethel.alpino.lassy - a wrapper for reading Lassy xml trees.
• aethel.utils contains general utilities:
  • aethel.utils.graph - definitions of simple graph-theoretic operations.
  • aethel.utils.viz - visualization of Lassy dependency graphs, useful for debugging.
  • aethel.utils.tex - export proofs and samples to latex code.

Subdirectory examples contains (or will contain) introductory jupyter notebooks. Subdirectory scripts contains (or will contain) high-level scripts for processing the corpus and lexicon.

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Requirements

Python 3.10+

If you intend to use the visualization utilities you will also need GraphViz.

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Citing

If you found this software or data useful in your research, please cite the corresponding paper:

@inproceedings{kogkalidis2020aethel,
  title={{\AE}THEL: Automatically Extracted Typelogical Derivations for Dutch},
  author={Kogkalidis, Konstantinos and Moortgat, Michael and Moot, Richard},
  booktitle={Proceedings of the 12th Language Resources and Evaluation Conference},
  pages={5257--5266},
  year={2020}
}