The Resources for Processing Bulgarian and Serbian – the brief overview of their Completeness, Compatibility, and Similarities Svetla Koeva, Cvetana Krstev, Ivan Obradoviş, Duško Vitas Department of Computational Faculty of Philology Faculty of Geology and Faculty of Mathematics Linguistics – IBL, BAS University of Belgrade Mining, U. of Belgrade University of Belgrade 52 Shipchenski prohod, Bl. 17 Studentski trg 3 ušina 7 Studentski trg 16 Sofia 1113 11000 Belgrade 11000 Belgrade 11000 Belgrade [email protected] [email protected] [email protected] [email protected] furthermore presupposes the successful Abstract implementation in different application areas as cross- Some important and extensive language resources lingual information and knowledge management, have been developed for Bulgarian and Serbain cross-lingual content management and text data that have similar theoretical background and mining, cross-lingual information retrieval and structure. Some of them were developed as a part information extraction, multilingual summarization, of a concerted action (wordnet), the others were multilingual language generation etc. developed independently. The brief overview of these resources is presented in this paper, with the 2. Electronic dictionaries emphasis on the similarities and differences of the information presented in them. The special 2.1 Bulgarian Grammatical Dictionary attention is given to the similarities of problems The grammatical information included in the encountered in the course of their development. Bulgarian Grammatical Dictionary (BGD) is divided into three types [Koeva, 1998]: category information 1. Introduction that describes lemmas and indicates the words clustering into grammatical classes (Noun, Verb, Bulgarian and Serbian as Slavonic languages show Adjective, Pronoun, Numeral, and Other); similarities in their lexicons and grammatical paradigmatic information that also characterizes structures. At present for both languages some lemmas and shows the grouping of words into equivalent language resources were developed, grammatical subclasses, i.e. — Personal, Transitive, moreover the formal approaches for the organization Perfective for verbs, Common, Proper for nouns, etc.; of those recourses are very similar. The goal of this and grammatical information that determines the paper is briefly to present these similarities while formation of word forms and shows the arranging of describing the integration between electronic words into grammatical types according to their dictionaries and lexical-semantic data bases inflection, conjugation, sound and accent alternations, (wordnets) of both languages. etc. The Bulgarian and Serbian wordnets have been The BGD is a list of lemmas where each entry is initially developed in the framework of the project associated with a label [Koeva, 2004a]. The label itself BalkaNet – a multilingual semantic network for the represents the grammatical class and subclass to which Balkan Languages which has been aimed at the the respective lemma belongs and contains a unique creation of a semantic and lexical network of the number that shows the grammatical type. All words in Balkan languages with a view to their integration in the language that belong to the same grammatical the global WordNet — an extensive network of class, subclass and have an identical set of endings and synonymous sets and the semantic relations existing sound / stress alternations are associated with one and between them in different languages which enables the same label. Each label is attributed with the cross-references between equivalent sets of words with corresponding formal description of endings and the same meaning. alternations — inflectional engine used is equivalent to a stack automaton. Although the existence of some The common origin of Bulgarian and Serbian, the differences in the format, the BGD represents itself a equivalent types of existing electronic resources and kind of DELAS dictionary [Courtois, 1990] and it is application approaches used offer not only the very compiled into a Finite-State Transducer. good basis for the comparative research but 2.2. Serbian Morphological Dictionary V651. The information attached to a lemma in the DELAS dictionary pertains to all forms of that lemma, Electronic dictionaries of Serbian consist of whereas morphological information attached to the morphological dictionaries of general lexica, inflected form in the DELAF dictionary is dictionaries of proper names, and the Serbian wordnet. characteristic for that form only. The system of morphological e-dictionaries of simple words in Serbian has been deveoped according to the 3. Morphological information in LADL model and described, with other types of electronic dictionaries of Bulgarian and dictionaries, in [Vitas & al., 2003]. Following this model the system is based on a dictionary of lemmas Serbian named DELAS. A dictionary of all inflectional forms, Regarding the PoS (part of speech), the Princeton named DELAF, is automatically generated on basis of Wordnet (PWN) and other wordnets that used PWN as morphological information attached to lemmas in a model consist of nouns, verbs, adjectives and DELAS. The most important piece of information adverbs. accompanying a DELAS lemma is the inflectional class it belongs to, which enables the generation of all 3.1. Nouns inflective forms of a lemma with accompanying Nouns in Bulgarian and Serbian are characterized by grammatical information. The information on the the following inflectional categories: inflective class is expressed by a code, e.g. N600 or
CATEGORY BULGARIAN SERBIAN Gender masculine, feminine, neutral Number singular, plural, counting form singular, plural, paucal Case vocative nominative, genitive, dative, accusative, vocative, instrumental and locative Definiteness definite, indefinite, definite - full form, definite - short form Animateness animate, inanimate Table 1. Grammatical features of nouns morphemes for masculine which specify the syntactic Bulgarian nouns are divided into grammatical functions – subject and others. subclasses with respect of their type (Common, Proper, Singularia tantum, Pluralia tantum) and Bulgarian masculine non-animate nouns after counting Gender. The category Gender with Bulgarian nouns is numerals and quantifiers are used in plural in a a lexical-semantic category, which means that a given counting form – (five textbooks), noun does not possess different word forms expressing (ten pine-trees). masculine, feminine and neuter although the noun In Serbian, nouns are morphologicaly realized in lemmas can be grammatically classified into the three seven cases. The category Gender is in Serbian classes: (chair) - masculine, (table) – inflectional category: for instance papa (pope) is feminine, and (dog) - neuter. masculine but its plural form pape is feminine. The category Case has lost its morphological Besides two main categories for number, singular and realization in the system of Bulgarian nouns and only plural, Serbian nouns also have the so called “paucal” vocative against nominative is kept with proper and form which represents a synthetic category of number common nouns (masculine and feminine) denoting and gender that is used with small numbers (two, three persons. Some concrete nouns also allow potential four): jedan lep zec (one pretty rabbit), dva lepa zeca generation of vocative in metaphorical usage. (two pretty rabbits), pet lepih zećeva (five pretty rabbits). Animatness is also the inflectional category The category Definiteness is realized by means of for masculine gender nouns: the form of the accusative indefinite and definite forms that incorporate the case is equal to the genitive case for the animate nouns definite morpheme into the word end. Special feature and to the nominative case for the inanimate nouns. of Bulgarian is the existence of two definite
Noun lemmas in the Serbian DELAS dictionary are the relative pronoun in plural both as a noun of marked with markers which sometimes determine the feminine gender (Izbeglice (f) koje (f) su juće stigle (f) noun in a more precise manner. For example, pluralia su izjavile (f)… – The refugees that arrived yesterday tantum is marked with the marker +PT as in pantalone said…) and as a noun of masculine gender (UNHCR denoting the concept lexicalized in PWN as şe pružiti pomoş za izbeglice (f) koji (m) žele da se {trousers:1, pants:1} and in the Bulgarian wordnet as integrišu u lokalnu sredinu – UNHCR will provide { :1, :1}. The markers +MG +FG help for refugees that want to integrate into the local are used to mark the natural male and female gender society). Finally, the marker +Pl marks a noun in (or sex) which does not necessarily match the singular which denotes a natural plural: braşa grammatical gender and which is important for (brothers) is inflected as a noun of feminine gender in agreement. This is the case, for example, with the singular and agrees as noun both with singular and noun izbeglica (refugee), which denotes persons of plural: Njena (s) braşa (s) su (p) dolazila (s) svaki dan both male and female sex. This noun is inflected as a (her brothers came every day). noun of feminine gender, agrees with the adjective as a noun of feminine or masculine gender in singular (za 3.2. Verbs svakog (m) izbeglicu (f) – for every refugee) and as a Verbs in Bulgarian and Serbian are characterized by noun of feminine gender in plural, and can agree with the following inflectional categories and their values: CATEGORY BULGARIAN SERBIAN Person first, second, third first, second, third Number singular, plural singular, plural Tense present, aorist, imperfect present, aorist, imperfect, future Mood indicative, imperative infinitive, imperative Participles present active, aorist active, imperfect past active, past passive active, past passive Voice active, passive active, passive Definiteness definite, indefinite, definite – full form, definite - short form Gender masculine, feminine, neuter masculine, feminine, neuter Gerund past active present active, past active Table 2. Grammatical features of verbs se, lexicalized in PWN as {dissolve:9, thaw:1, Bulgarian Verbs are classified in subclasses with unfreeze:1, unthaw:1, dethaw:1, melt:2} an in the respect of Transitivity (transitive and intransitive), Bulgarian wordnet as { :1, :1, Perfectiveness (perfective and imperfective), and :1, :1, :1, Personality (personal, third personal and impersonal), :1}. Lexical reflexivity in both languages while the Serbian verbs are classified according to the is expressed by the lexical particle se (and si for first two features. Bulgarian). Formally identical verbs can also express Verb lemmas in Serbian are characterized by the either transitive or intransitive meaning, such as following markers: for aspect imperfective +Imperf {svirati:1b} denoting the concept lexicalized in PWN and perfective +Perf, for reflexiveness reflexive +Ref as {play:3} and in the Bulgarian wordnet as {:3} and irreflexive +Iref, and for transitivity transitive +Tr as intransitive verb (The band played all night long), and intransitive +It. or {svirati:1a} denoting the concept lexicalized in Many verbs in the two languages can be both PWN as {play:7} and in the Bulgarian wordnet as He plays the flute imperfective and perfective, such as and { :1} as transitive verb ( ). adresirati which denote the concept lexicalized in Synsets that contain the same verb, in one case as PWN as {address:3, direct:12}. Many formally equal reflexive and in the other as irreflexive are often cause / caused verbs can express both reflexive and irreflexive linked by the relation. The transitive / meaning, such as {topiti:1a} lexicalized in PWN as intransitive forms have to have separate meanings in {melt:1, run:39, melt down:1} and in the Bulgarian PWN. This is not the case with the aspect – perfective wordnet as { :1, :1, :1, verbs which were not generated by prefixing should be :1, :1, :1} and topiti in the same synset with the imperfective verb. Bulgarian imperative has two declined forms - 2nd perfect, pluperfect, future (past and perfect), and person singular and plural, in comparison with Serbian conditional. where three declined forms: 2nd person singular, 1st Infinitive in Serbian and Gerunds in both languages and 2nd person plural, are realized. are indeclinable. Bulgarian participles are specified for aspect and decline according to number, gender and definiteness. 3.3. Adjectives Serbian participles are specified for aspect and decline The realized categories with adjectives in Bulgarian according to number: singular or plural, and gender: and Serbian are similar too – main differences are masculine, feminine, or neutral. observed with categories Case and Animateness. Adjectives are characterized by the following Participles in both languages are used to form morphological categories and their members: compound tenses, both in active and passive voice: CATEGORY BULGARIAN SERBIAN Gender masculine, feminine, neutral masculine, feminine, neutral Number singular, plural singular, plural, paucal nominative, genitive, dative, accusative, vocative, Case instrumental, and locative definite, indefinite, definite - full Definiteness definite, indefinite form, definite - short form Comparison positive , comparative, superlative positive, comparative, superlative Animateness animate, inanimate Table 3. Grammatical categories with adjectives 3.4. Adverbs Adverbs in traditional Bulgarian and Serbian In order to merge the language data existing in BulNet grammars are considered as indeclinable word types, and BGD a solution was accepted to assign an although for many of them comparison exists: for additional grammatical note to each literal thus linking example, , brzo (rapidly), - , brže (more it with the BGD lemma's label [Koeva, 2004b]. All rapidly) and - , najbrže (the most rapidly). labels for BGD entry forms that are found in the These are usually treated as separate lemmas but a BulNet have been entered as values of the LNOTE paradigmatic analisys in the scope of the grammatical tag in the XML format. Most of the morphological category Comparison is also literals which were not recognized are either acceptable. There is another level of comparison for specialized terms that have no place in a grammatical adjectives and adverbs in Serbian which is realized by dictionary of the common lexis (often written in Latin) the prefix po- and superlative: ponajbrže, which or compounds. The contradictory cases where two or relativizes the superlative and denotes, in this case, the more labels were associated with one and the same fastest way among the slow ways. literal were solved manually. 4. Language resources integration 4.2. Serbian resources 4.1. Bulgarian resources The Serbian wordnet is less developed: it covers at present approximately one fifth of the Serbian general There are three large Bulgarian resources: Bulgarian lexicon, but it is constantly being developed [Krstev & WordNet (BulNet) which covers approximately one al., 2004a]. In the course of its development it has third of the general Bulgarian lexicon [Koeva & al., been enriched with information that pertains to 2004], BGD - encoding lemmas and corresponding inflexion of literals – simple words. A software tool inflection types and Bulgarian Frame Lexicon - specially designed for this purpose is used which encoding the arguments of the verbs and their enables automatic transfer of all information on the semantic features. The combination of these resources inflectional class of a literal from the morphological results in their mutual enhancement, their expansion dictionary into the wordnet where it becomes the and reliable validation. content of the