26.02.2009 LG617 - XLE Lab 1

Kakia Chatsiou A brief introduction to XLE

LG617 A brief introduction to XLE

Kakia Chatsiou

achats@essex.ac.ukDept of Language and Linguistics

University of Essex

26.02.2009 LG617 - XLE Lab 2

Kakia Chatsiou A brief introduction to XLE

Outline

• About XLE• Where is XLE used?

– ParGram Project

• Project Objectives• Participating Members

– Powerset– XLE Web interface

• A closer look at XLE– Grammar architecture– Inspecting a basic grammar .lfg file– XLE interface– XLE vs LFG notations

• Hands-on Session

26.02.2009 LG617 - XLE Lab 3

Kakia Chatsiou A brief introduction to XLE

About XLE

• XLE stands for Xerox Linguistics Environment• Under current development at PARC (Palo Alto Research

Center, USA)• A computational environment developed to facilitate the

writing and debugging of Lexical Functional Grammars• C-structure, f-structure, s-structure, and further projections

can be defined • Implemented in C; works in Unix, Linux, MacOS. • Integrates a morphological analyser employing Finite State

Technology• Can be used for both parsing and generation• Includes tools for various grammar development activities

(such as analysing performance, test-suites)

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Kakia Chatsiou A brief introduction to XLE

Where is XLE used?

• ParGram Project• The core technology used in the consumer search

engine based on natural language processing which is currently under development by PowerPowerset set

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Kakia Chatsiou A brief introduction to XLE

Where is XLE used? :: ParGram Project ::

Project Objectives

• Broad coverage grammars– Inclusion of important and frequently occurring constructions– Linguistically motivated analyses

• Parallel and crosslinguistic development of grammars between the participating members– All grammars are guided by a common set of linguistic principles

and a commonly agreed upon set of grammatical analyses and features

– Identical treatment of core crosslinguistic phenomena

• Methods in grammar engineering– Common test methods and evaluation strategies– Balance between efficiency, performance, reliability and

maintainability across grammars

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Kakia Chatsiou A brief introduction to XLE

Participating Members

PARC, CAChinese, English,

French

EssexGreek, Welsh

ManchesterArabic

OxfordMalagasy

DCU, IrelandChinese, English, French, German,

Japanese, Spanish

Fuji XEROXJapanese

Bergen, NorwayGeorgian, Norwegian, Tigrinya

Ho Chi MinchVietnamese

DebrecenHungarian

IMS, StuttgartGerman

KonstanzUrdu

Sabanci, IstanbulTurkish

Where is XLE used? :: ParGram Project ::

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Kakia Chatsiou A brief introduction to XLE

• a Silicon Valley Company, currently building a transformative consumer search enginesearch engine based on natural language processing:– It is based on technologies that take advantage of the structure and

nuances of natural language– It offers an innovative approach to searching:

• It breaks the confines of keyword search queries using both keywords, short phrases and natural language

• Makes search more natural and intuitive• Aims at fundamentally changing how we search the web and at the same

time delivering higher quality results• currently searching Wikipedia with the help of FreeBase as the semantic

knowledge database

(source: http://www.powerset.com )

Where is XLE used? :: Powerset Search Engine ::

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Kakia Chatsiou A brief introduction to XLE

Where is XLE used? :: Powerset Search Engine ::

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Kakia Chatsiou A brief introduction to XLE

• a web-based tool for parsing LFG grammars using the XLE tool

• outputs c-structures, f-structures and mrs-structures.

• allows the user to choose a grammar and type in a sentence to be analyzed. The sentence is then processed by the XLE parser, and the resulting structures are displayed.

• has a facility for uploading (small) user grammars, mainly for teaching purposes.

Where is XLE used? :: The XLE Web Interface ::

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Kakia Chatsiou A brief introduction to XLE

A closer look at XLE

• Grammar architecture?• Inspecting a basic grammar .lfg file

– Inspecting the config file?– Inspecting a rule– Inspecting a lexical entry

• XLE interface• XLE vs LFG notations

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Kakia Chatsiou A brief introduction to XLE

Other Finite State Tools

Tokenizer

Morpholo-gical

AnalyserFST

Lexicon(s)(Hand-written

OrAutomatically

Extracted)

LFG Grammar

(rules, templates)

Grammar Resources(parsing

and generating)

A closer look at XLE :: Basic Grammar Architecture ::

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Kakia Chatsiou A brief introduction to XLE

A closer look at XLE :: Inspecting a grammar file ::

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Kakia Chatsiou A brief introduction to XLE

A closer look at XLE :: XLE interface ::

C-structur

e

f-structur

e

Packed representa-tion of f-structures

Representa-tion logical

choices (in cases of

ambiguity)

% parse {Mary saw the boys with the telescope}parsing {Mary saw the boys with the telescope}2 solutions, 0.01 CPU seconds, 23 subtrees unified

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Kakia Chatsiou A brief introduction to XLE

LFG notation XLE-equivalent Description↑ ^ f-structure metavariable↓ ! f-structure metavariable= = defining equality≡ = meta-category definition=c =c or =C constraining equality∈ $ set membership¬ ~ negation (complementation)d d existential constraint (standard

notation)∃ d d existential constraint (Sadler)← <- off-path constraint→ -> off-path constraint⊑ << subsumption (subsumes)⊒ >> subsumption (is subsumed by){ a | b | c | ... | z } { a | b | c | ... | z } disjunction( a ) { a } optional f-structure constraint

A closer look at XLE :: XLE vs LFG Notations ::

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Kakia Chatsiou A brief introduction to XLE

Hands-on Session

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Kakia Chatsiou A brief introduction to XLE

References / Sources

• ParGramhttp://www2.parc.com/isl/groups/nltt/pargram/

• XLE Web Interface Documentation: http://maximos.aksis.uib.no/Aksis-wiki/XLE-Web

• XLE Documentationhttp://www2.parc.com/isl/groups/nltt/xle/doc/xle_toc.html

• Powersethttp://www.powerset.com/

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Kakia Chatsiou A brief introduction to XLE

Thank you!

For more information and updates on the progress of the project visit

http://privatewww.essex.ac.uk/~achats/projects/greekgram/index.html