Stefanie Geldbach: Lexicon Exchange in MT
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Stefanie Geldbach Lexicon Exchange in MT The Long Way to Standardization Abstract in diff erent systems. MT systems typically fol- Th is paper discusses the question to what extent low a lemma-oriented approach for the repre- lexicon exchange in MT has been standardized sentation of homonymy which means that diff e- during the last years. Th e introductory section rent semantic readings of one word are collapsed is followed by a brief description of OLIF2, a into one entry. Th e entry for Maus in the Ger- format specifi cally designed for the exchange of man monolexicon of LexShop 2.2 (see Section terminological and lexicographical data (Section 3.4) illustrates this approach. Th is entry contains 2). Section 3 contains an overview of the import/ (among others) following feature-value pairs: export functionalities of fi ve MT systems (Promt Expert 7.0, Systran 5.0 Professional Premium, CAN “Maus” Translate pro 8.0, LexShop 2.2, OpenLogos). CAT NST Th is evaluation shows that despite the standar- ALO “Maus” dization eff orts of the last years the exchange of TYN (ANI C-POT) lexicographical data between MT systems is still not a straightforward task. Th e feature TYN (type of noun) which indica- tes the semantic type of the given noun has two 1 Introduction values, ANI (animal) and C-POT (concrete-po- Th e creation and maintenance of MT lexicons tent) representing two diff erent concepts, i.e. the is time-consuming and cost-intensive. Th erefore, small rodent and the peripheral device. the development of standardized exchange for- Term bases usually are concept-oriented mats has received considerable attention over the which means that diff erent semantic readings of last years. On the way to standardization a num- homonyms are stored in diff erent entries. Th e ber of obstacles has to be overcome (Lieske et al. defi nition given in the entry for Maus in the 2001, Thurmair 2006): multilingual termbank EURODICAUTOM of MT developers use diff erent data categories the European Commission (see Fig. 1) which re- and values in order to represent lexicographical presents only one concept (here, the peripheral data. While the representation of some data ca- device) clearly illustrates this approach: If a ho- tegories such as gender is largely uncontroversi- monymous entry such as Maus is to be imported al, much less agreement is to be found when it from a lemma-oriented MT lexicon to a concept- comes to subcategorization, semantic features or oriented termbase the diff erent readings of the subject fi elds. Th erefore, the development of a entry have to be identifi ed which is a non-tri- potential standard involves both the defi nition vial task. of standardized data categories and values as well as the conversion of proprietary data categories 2 What is OLIF2? to these standards. OLIF2 is an open XML-compliant standard In the case of homonymy, there is possibly specifi cally intended for the exchange of lexi- no one-to-one correspondence between entries cographical and terminological data released to LDV FORUM – Band 21(1) – 2006 27 Geldbach Fig. 1: EURODICAUTOM entry (http://europa.eu.int/eurodicautom/Controller) the public in 2002 (cf. www.olif.net). OLIF2 ries (canonical form, language, part of speech, has been developed by the OLIF Consortium, subject field and semantic reading). a group of major MT developers and users led Cross-reference data define semantic relations by SAP1. Initially, OLIF was intended to facilita- between the given entry and other entries te the exchange of lexical data between diff erent such as hyponymy, synonymy or meronymy. MT systems. OLIF2, however, aims at integra- Transfer data define the transfer relations bet- ting both MT data and terminological resources ween the given entry and other entries in dif- by bridging the gap between the lemma-orienta- ferent languages. Multiple transfers are pos- tion of most MT lexicons and the concept-ori- sible with each transfer group representing a entation of terminology management systems. single, unidirectional relation. “An OLIF entry is defi ned as a collection of mo- nolingual data on a specifi ed sense of the word A sample OLIF entry is shown in Figure 152. or phrase, with optional links to represent trans- fer and cross-reference relations” (McCormick 3 Lexicon Exchange Functionalities in 2002:1), which means that homonyms such as Current MT Systems Maus or table are stored in two diff erent entries. Th e following section contains a detailed de- Th e body of OLIF entries contains three main scription of the lexicon exchange functionalities data groups: of fi ve major MT systems which is based on the information given in the respective user guides Monolingual data: each entry may contain only as well as the tests I conducted myself. Following one monolingual group. Each OLIF entry is systems were tested, using the language pair Ger- specified by a unique set of five data catego- man – English each: 28 LDV FORUM Lexicon Exchange in MT @Promt Expert 7.0, www. translate.ru. A demo version with a German or English GUI can be downloaded at http://www.e-Promt.com/. Systran 5.0 Professional Premium, http://www.systransoft.com. Translate pro 8.0, a demo version is available Fig. 2: Promt import format at http://www.lingenio.com. Comprendium LexShop 2.2, more information For each system, it will be described how the user at http://www.braintribe.com. can create new lexicon entries and which fi le for- OpenLogos, which can be downloaded from mats are supported for the import and export of http://logos-os.dfki.de/. user dictionaries. Th e focus is on the linguistic Fig. 3: @Promt Dictionary Editor Band 21(1) – 2006 29 Geldbach quality of the lexicographical data, i.e. the question whe- ther the exchanged entries are complete or whether impor- tant linguistic information has to be recoded by hand. In or- der to test the linguistic quali- ty the import and export test fi les also contained potentially diffi cult examples such as re- fl exive verbs, verbs with com- plex subcategorization or ho- monyms. 3.1 @Promt Expert 7.0 Promt user dictionaries are created and maintained with the help of the Dictionary Editor which guides the user through the coding process. After entering the source language word the user Fig. 4: SL-TL mappings in the Dictionary Editor has to select part of speech (it is possible to code nouns, verbs, adjective and adverbs), infl ection Promt off ers, however, an add-on for the au- type, translation and grammatical information, tomatic creation of dictionaries which enables notably semantic and government information. the user to import glossaries stored as tab-deli- Th e user has the choice between two coding le- mited text fi les (TXT) into the user dictionary vels, beginner and professional. Some informa- which is explained in the ADC User Guide. Im- tion such as government can only be defi ned at port fi les have to be written in a specifi c notation the professional level. which is shown in Figure 2. Th e location of dictionary fi les in the fi le sys- Th e only obligatory fi elds are the key, i.e. the tem is controlled by Promt and not revealed source language (SL) word, and its respective to the user. A dictionary may be accessed as a translation in the target language (TL). In order fi le only when it is saved to a dictionary archi- to improve the import result following fi elds can ve using the so-called Promt Backup. Dictio- be added: nary archives, which are stored in a proprietary format with the extension ADC, can be used as PartOfSpeech: the part of speech of the key. It is backup copies or for copying user dictionaries to possible to choose between verbs (v), adjecti- other Promt users; they cannot be imported into ves (a), nouns (n) and adverbs (adv). other MT systems, however. At present, Promt InProp: gender and number of the SL word. Fol- off ers no possibilities of exporting user dictiona- lowing values are possible: masculine (m), fe- ries which limits the integration of Promt user minine (f), neuter (n), plural (pl), masculi- dictionaries into other MT systems. ne plural (mpl), feminine plural (fpl), neuter plural (npl). 30 LDV FORUM Lexicon Exchange in MT OutProp: gender and number of the TL word. selected the frame for the second reading OutComment: comments and domain defini- of bestehen as in (2) the Dictionary Editor tions. changed the frame of the first reading (see Fig. 4) to aus jmdm(etwas) bestehen / to insist Diff erent translations of homonymous SL words, of smbd(smth) and added a further transitive e.g. Mutter or bestehen, are separated by semi- frame, presumably taken from the reading colons. bestehen / to pass. The information given by Th e glossary as shown in Figure 2 can be impor- the user was ignored. As a result, Promt failed ted into an existing user dictionary using either in- in disambiguating the different readings of teractive or fully automatic mode. Th e import result the German sample sentences and produced of the sample fi le is shown in Figure 3. the following translations for (1) and (2): Th e symbol «u» marks entries which have not been verifi ed yet, which means their grammatical (3) The politician insists{consists} on his{its} information has been computed by the system suggestion{proposal}. and should be checked by the user. Th e exclama- (4) The soup insists{consists} of water. tion mark (!) signals which part of the entry, i.e.