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Proper Nouns in Czech Corpora

Proper Nouns in Czech Corpora

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Proper Nouns in Czech Corpora

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  1. Proper Nouns in Czech Corpora Magda Ševčíková sevcikova@ufal.mff.cuni.cz Institute of Formal and Applied Linguistics Faculty of Mathematics and Physics Charles University in Prague Czech Republic

  2. Outline • Introduction • Proper nouns in corpora of Czech: current state • Corpus SYN2000 • Prague Dependency Treebank 2.0 • Proposal of a complex proper noun annotation within the Prague Dependency Treebank 2.0 • Final remarks sevcikova@ufal.mff.cuni.cz

  3. Introduction • proper nouns • lacking a generic meaning • denoting individuals, institutions etc. • identifying them as unique items • proper nouns in NLP • question answering • information extraction • machine translation • pan Zelenýshould not be translated into Mr Green • Frankfurt am Main or Frankfurt nadMohanem, but not a combination of both (e.g., Frankfurt nad Main) • explicit annotation of proper nouns needed sevcikova@ufal.mff.cuni.cz

  4. Proper nouns in corpora of Czech: current state • two large corpora of Czech as sources of proper nouns: • SYN2000 • 100 million tokens • morphological annotation • morphological lemmas and positional tags • no explicit annotation of proper nouns • Prague Dependency Treebank 2.0 (PDT 2.0) • morphologically and syntactically annotated • very basic annotation of proper nouns • at the morphological layer • at the deep-syntactic (tectogrammatical) layer sevcikova@ufal.mff.cuni.cz

  5. Proper nouns in SYN2000http://ucnk.ff.cuni.cz • proper nouns were not marked • other characteristics used for searching for proper nouns • capitalization • only proper nouns capitalized in Czech (in comparison, e.g., to German) • however, it is not a sufficiently distinctive feature (sentence beginnings) • context patterns • for instance, Mr Xxx / President Xxx sevcikova@ufal.mff.cuni.cz

  6. sevcikova@ufal.mff.cuni.cz

  7. Proper nouns in PDT 2.0http://ufal.mff.cuni.cz/pdt2.0/ • basic annotation of proper nouns • at the morphological layer • each token was assigned a morphological lemma and a positional tag • lemma flag for marking of proper nouns • at the tectogrammatical layer • each sentence represented by a labeled dependency tree structure (consisting of nodes and edges) • special means for annotation of selected phenomena concerning proper nouns sevcikova@ufal.mff.cuni.cz

  8. PDT 2.0: Morphological layer • proper noun type indicated by a value of a special flag which was attached to lemmas of proper nouns by a separator • Jan_;Y, Zelený_;S • seven flag values • first names, surnames, inhabitant names, geographical names, institution names, product names, other names • convenient for annotation of one-word proper nouns • insufficient for more complex proper nouns • misinterpretations: • Frankfurt_;G nad Mohanem_;G • Vysoký_;K škola ekonomická (University of Economics) sevcikova@ufal.mff.cuni.cz

  9. PDT 2.0: Tectogrammatical layer • no complex annotation of proper nouns • annotation means for selected phenomena only • person names • node attribute is_name_of_person • non-inflected street names, book titles etc. accompanied by a generic noun • functor ID • book titles etc. which have a form of a prepositional group and are not accompanied by a generic noun • an ‘artificial’ node with lemma #Idph • besides these individual cases, proper nouns were treated as common parts of a sentence sevcikova@ufal.mff.cuni.cz

  10. (a) (b) (a) person name Klára Nováková Malá (b)V sobotu v poledne je hezký film (lit.: ‘On Saturday at Noon’ is a nice film) (c)Šli jsme ulicí Spálená (We walked through the street.instr Spálená.nom) (d)Šli jsme ulicí Spálenou(We walked through the street.instr Spálená.instr) (e)Šli jsme Spálenou(We walked through Spálená.instr) (instr for instrumental case, nom for nominative case) (c) (e) (d) sevcikova@ufal.mff.cuni.cz

  11. Proposal of a complex proper noun annotation within PDT 2.0 • proper noun type defined at each proper noun • proper noun classification • annotation of one-word proper nouns as well as more complicated proper noun structures • four structure types to be annotated • the inner structure of more complex proper nouns described as a non-dependency relation • tectogrammatical layer sevcikova@ufal.mff.cuni.cz

  12. Proper noun classification for Czech • two-level classification • 1st level: five super-types of proper nouns • personal names, geographical names, institution names, artefact names, media names • (+ two more types: temporal expressions, numerical expression occurring in postal addresses) • 2nd level: proper noun types • e.g., types of geographical names: street/square names, city/town names, state names etc. • underspecification allowed • each type encoded by a unique two-character tag • gs for street/square names, gu for city/town names • g_ for a geographical name of an unknown type sevcikova@ufal.mff.cuni.cz

  13. Structure types to be annotated (i) one-word proper nouns • John (ii) multi-word proper noun expressions • Vysoká škola ekonomická(University of Economics) (iii) complex proper noun expressions • Frankfurt nad Mohanem (iv) containers • Jan Zelený sevcikova@ufal.mff.cuni.cz

  14. (i) Annotation of one-word proper nouns • proper noun type indicated at each proper noun • new node attribute: NE_roles • value set corresponds to all proper noun type tags (and container tags) • substitutes the current is_name_of_person attribute sevcikova@ufal.mff.cuni.cz

  15. (ii) Annotation of multi-word proper noun expressions • every constituent of a multi-word proper noun expression has a node of its own • at all nodes, the same value of the NE_roles attribute occurs • edges in the sub-tree labeled with a new functor NEPART • syntactic function of the whole expression indicated by the functor of the governing node Vyučuje na Vysoké škole ekonomické (He teaches at University of Economics) sevcikova@ufal.mff.cuni.cz

  16. (iii) Annotation of complex proper noun expressions • every constituent has a node of its own • a main part (Frankfurt) and an embedded part (Mohan) • type of the embedded part indicated by the value of the NE_roles attribute at the embedded part, type of the whole expression at the main part • relation between the main and the embedded part labeled with the NEPART functor Navštívil Frankfurt nad Mohanem (He visited Frankfurt am Main) sevcikova@ufal.mff.cuni.cz

  17. (iv) Annotation of containers • the #Idph node as the governing node of the whole container • container type indicated by the value of the NE_roles attribute at the #Idph node • proper noun types of the constituents defined by the values of their belonging NE_roles attributes • relations between the #Idph node and constituents labeled with the NEPART functor Novým ředitelem je Jan Zelený (Jan Zelený is the new director) sevcikova@ufal.mff.cuni.cz

  18. Final remarks • annotation of proper nouns in corpora • linguistic research • NLP subtasks • complex proper noun annotation within PDT 2.0 • tectogrammatical layer more convenient than the morphological one • annotation means and rules proposed • future work • further elaborate the proposed means and rules • manual annotation of sample data • development of automatic annotation tools sevcikova@ufal.mff.cuni.cz