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Issues in Building and Exploiting Latin Language Resources. Marco Passarotti Università Cattolica del Sacro Cuore, Milan (Italy). Outlook. Specific issues of ancient languages and texts Language Resources for Latin: Annotated corpora NLP The Index Thomisticus Treebank IT-VaLex
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Issues inBuilding and ExploitingLatin Language Resources Marco Passarotti Università Cattolica del Sacro Cuore, Milan (Italy)
Outlook • Specific issues of ancient languages and texts • Language Resources for Latin: • Annotated corpora • NLP • The Index Thomisticus Treebank • IT-VaLex • Exploiting Latin Language Resources: • Latin Word Order • From Syntax to Semantics: Textual Clustering (1) • From Lexicon to Semantics: Textual Clustering (2) • Is Latin a less-resourced language? What’s still missing?
Specific Issues of Ancient Languages and Texts • No native speakers • Several interpretations of the same text • Several versions of the same text • No digital born texts: relevance of the original source • Dead language = “closed” corpus/lexicon • Diachrony & Dialects: not just one Ancient Greek or Latin • Representativeness: our data are just the top of the iceberg • Not the WSJ, but mostly literary and philosophical texts • Not (just) for NLP purposes, but for the text itself • Computational linguists not used to deal with ancient languages (LREC ’12: one paper on Latin!). BUT things are changing: see TLT, ACRH etc. • Pencil-and-paper scholars (Classicists) not used to deal with digital LRs, NLP tools and modern linguistic theories: difficult to find students with required expertise. BUT things are changing…
Annotated CorporaTreebanks • Collaboration between CIRCSE and Perseus: • Latin Dependency Treebank: Classical Latin (approx. 55,000 annotated tokens) • Index Thomisticus Treebank: Thomas Aquinas opera omnia (approx. 180,000 annotated tokens) • PROIEL: University of Oslo • Several translations of the New Testament: Latin, Greek, Old Church Slavonic, Armenian, Gothic (approx. 120,000 annotated tokens) • All dependency-based (via PDT): common guidelines
NLP Tools (1) • Morphological analysers: Words (Whitaker), Morpheus (Perseus), LEMLAT (ILC-CNR) • Data-driven NLP (best rates) Source of Data: Index Thomisticus Treebank Training set: 61,024 tokens (2,820 sentences) Test set: 7,379 tokens (329 sentences) • PoS Tagging (HMM-based HunPos tagger): • 96.75: coarse-grained PoS + fine-grained PoS • 89.90: with morphological features • Syntactic Parsing (DeSR): • 80.02 (LAS); 85.23 (UAS); 87.79 (LA)
NLP Tools (2)13 Centuries… • IT-Train: 44,195 – IT-Test: 5,697 • LDT-Train: 47,662 – LDT-Test: 5,481 • Parser: DeSR
The Index Thomisticus Treebankhttp://itreebank.marginalia.it
The Corpus • Index Thomisticus (Busa): • opera omnia of Thomas Aquinas • 119 works + 61 of other authors • approx. 11 million words • morphologically tagged & lemmatized • Index Thomisticus Treebank: • Dependency-based = LDT & PROIEL • approx. 180,000 words (10,000 sentences) • from: • Scriptum super Sententiis Magistri Petri Lombardi • Summa contra Gentiles • Summa Theologiae
From FGD to Annotation Layers language is “a system of means of expression with some definite aim” (Theses of the Prague Linguistic Circle, 1929) • L0 (w) Words (tokens): automatic segmentation only • L1 (m) Morphology: Tags (full morphology, 11 categories) + Lemma • L2 (a) [FORM] Analytical Layer (surface syntax): dependency-based Analytical dependency functions: Pred, Sb, Obj, Adv, Atr, Pnom… • L3 (t) [MEANING] Tectogrammatical Layer (underlying syntax): dependency-based • Autosemantic words only (no function words and punctuations) • Functors (valency): Arguments vs. Adjuncts • Arguments: ACT, PAT, EFF, ADDR, ORIG • Adjuncts (~ 50), semantically defined: LOC, TWHEN, MANN, COND,... • Ellipsis resolution & Coreference (grammatical only: relative clauses, control-modals, pronouns) • Topic/focus articulation (deep word order)
In eodem enim instanti terminatur alteratio ad dispositionem quae est necessitas , et generatio ad formam;
Dynamic Valency Lexicon IT-VaLex http://itreebank.marginalia.it/itvalex/
Valency Number of obligatory complementations of a word • ‘arguments’ vs. ‘adjuncts’ • actants vs.circonstants • ‘inner participants’ vs. ‘free modifications’
From Syntax to Semantics.Textual Clustering (1) R Enviroment for Statistical Computing Package: cluster (function DIANA)
Clustering • deals with finding a structure in a collection of (un)labeled data • the process of organizing objects into groups (clusters) whose members are similar in some way • a cluster is a collection of objects which are “similar” to each other and are “dissimilar” to the objects belonging to other clusters
Textual Clustering for WSD • Distributional Hypothesis (Harris, 1954) words that are used in similar contexts tend to have the same or related meanings • Firth (1957) “You shall know a word by the company it keeps”
Lemma forma • 18,357 occurrences in the IT • 5,191 occurrences of forma in the IT-TB • a ‘technical’ word in Thomas, showing high polysemy • 4 main meanings in the lexicon of Thomas by Deferrari & Barry (1948-1949): • “form, shape”, synonym of figura • “form”, the actualizing principle that makes a thing to be what it is • “mode, manner” • “formula”
From Lexicon to Semantics.Textual Clustering (2) R Enviroment for Statistical Computing Packages: tm, RTextTools, Deducer(Text), lsa …you shall know a text by the words it keeps
dist = euclidean - hclust = ward Seneca: Dialogues Seneca: Tragedies Jerome Thomas
A BLaRK-like Set for Latin • Modules and Tools • Text pre-processing: named-entity recognition • Lemmatization and morphological disambiguation: PoS taggers (diachrony) • Syntactic analysis: parsers and shallow parsing (diachrony) • Anaphora and ellipsis resolution • Semantic and pragmatic annotation: coreference, semantic roles, TFA • Applications • Entering and acquiring information: digitization & OCR systems (images of original sources) • Against sparsity: common on-line infrastructure for ancient languages LRs • e-learning facilities for teaching ancient languages with LRs and NLP tools • Data • Texts: • more treebanked data from more eras • TGTS-like annotated texts • aligned translation(s) • Lexica (mono-/multilingual): • semantic-based valency lexicon: semantic roles + semantic features of the arguments • wordformation-based lexicon