LG617 A brief introduction to XLE

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Kakia Chatsiou A brief introduction to XLE

LG617 A brief introduction to XLE

Kakia Chatsiou

[email protected] of Language and Linguistics

University of Essex

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Outline

• About XLE• A closer look at XLE

– Grammar architecture– Getting started– Inspecting a basic grammar .lfg file– XLE interface– XLE vs LFG notations

• Hands-on Session • Where is XLE used?

– ParGram Project– Powerset – XLE Web interface

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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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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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• runs on the unix4 server• can be accessed via a Secure Shell (SSH)

(Start>Network Services>Secure Shell)• We will use the emacs editor to edit the XLE

grammar files (offers syntax colouring and an LFG toolbar for .lfg files)In the SSH command line, type

emacs

• Open a grammar file (Ctrl-x Ctrl-f or File>Open file); they normally have an .lfg extension

A closer look at XLE :: Getting Started ::

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

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Configura-tion

Section

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Rules Section

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LexiconSection

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Grammar Version ID

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Language ID

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Component ID

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XLE version

ID

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4 dashes signal the

end of each

section/ file

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The default

categorywhen

parsing

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specification of which lexical entries, and rule are given

precedence(here

precedence is given to

the grammar with version

ID STARTER and language ID LANGUAGE)

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list of the grammatical

relations which must

be subcategori-sed for in order to

appear in theargument list of the PRED

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list of attributes

whosevalues

must contain a PRED

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Phrasal category

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Schema / f-structure information

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Morpho-logicalmarker

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% create-parser {demo-eng.lfg}

% 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

A closer look at XLE :: XLE interface ::

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C-structur

e

f-structur

e

Packed representa-tion of f-structures

Representa-tion of logical

choices (in cases of

ambiguity)


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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)← <- 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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Hands-on Session

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Outline

• About XLE• A closer look at XLE

– Grammar architecture– Getting started– Inspecting a basic grammar .lfg file– XLE interface– XLE vs LFG notations

• Hands-on Session • Where is XLE used?

– ParGram Project– Powerset – XLE Web interface

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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

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

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

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About Powerset a Microsoft-partner 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

– Its technology has recently made into the Microsoft Live Search Engine(source: http://

www.powerset.com )

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

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• 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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References / Sources

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

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

• XLE Documentation

http://www2.parc.com/isl/groups/nltt/xle/doc/xle_toc.html

• Powersethttp://www.powerset.com/

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Thank you! Next week (March 5th) • Dependency Constructions

– Weak Crossover and Traceless UDCS: Dalrymple, Kaplan and King (Kakia)

– Tough Contructions: Dalrymple and King (Budour)

Papers still available:• Morphology-Syntax Interface: Lexical sharing

– Turkish Suspended Affixation: Broadwell – Preposition Determiner Contractions: Wescoat

• On Grammatical Functions – Polish Subjectless Constructions: Kibort – Nature of OBJ: Borjars and Vincent

• Functional and Lexical Verbs – English Auxiliaries: Falk(http://courses.essex.ac.uk/lg/lg617/sessions08.html)

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Thank you!

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

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

LG617 A brief introduction to XLE

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