The Prague Dependency Treebank

 Introduction | PDT as a project | Text Sources | Inner Format | PDT 1.0 | Future | Support | References

(abridged version of the part of paper:  E. Hajicova. Dependency-Based Underlying-Structure Tagging of a Very Large Czech Corpus, see References)

Since the very first step in the formulation of the Praguian project of Czech National Corpus  by a group of Czech linguists (Institute of Formal and Applied Linguistics, Institute of Theoretical and Computational Linguistcs) from Charles University  in Prague and Masaryk University  in Brno, it has been quite clear to all of us that for the outcome of our project to have a boarder relevance and a manysided use we cannot confine ourselves to a mere compilation of a very large corpus of Czech texts. We have been aware that in order to make the corpus really useful for future users, be they linguists or developers of natural language processing systems of any kind, we have to design annotation schemes and develop tools that would allow us to add as much linguistic information as possible. Having the advantage of a long and fruitful tradition of theoretical and computational linguistics and inspired by the research resulting the  Penn Treebank, the project group has decided to build so-called Prague Dependency Treebank (PDT).

The following three points are characteristic for the theory underlying the PDT, fully visible at the highest, tectogrammatical level:

(i) Its theoretical background is a dependency-based syntax (handling the sentence structure as concentrated around the verb and its valency, but containing a further dimension, namely coordination); among the reasons for the choice of a dependency based syntax we would like to stress first of all its relative economy and its perspicuous, immediate correspondence to the empirical data.

(ii) The nodes of the dependency tree (more exactly, of a more-dimensional network) are labeled by complex symbols (consisting of lexical, morphological and syntactic parts). Thus, the label of every node contains symbols expressing all the information contained in the grammatical position of this word and relevant for a semantic (more exactly, semantico-pragmatic) interpretation. This makes the output representations, or the trees of our treebank, useful not only for practical applications such as parsing, but also for its inclusion into an integrated theoretical description encompassing all layers from the outer (phonetic or graphemic) shape of the sentence to its semantico-pragmatic representation, be it in the form of truth-conditionally based intensional semantics, or in that of a framework paying more attention to the embedding of the sentence in context.

(iii) The dependency tree is understood as projective, and its relationships to the morphemic representation of the sentence (a string of symbols, the order of which corresponds to the surface word order) are handled by means of specific rules.

Prague Dependency Treebank as a project

The Prague Dependency Treebank (PDT) is a long-term project with two major phases. In the first phase (1996-2000), the morphological and syntactic analytic  layers of annotation have been completed and made together with the preview of tectogrammatical layer annotation available as  PDT 1.0. During the second phase (2000 - 2004, Center for Computational Linguistics), the tectogrammatical layer of annotation will proceed and the PDT 2.0 will be available in the end.

The structure of Prague Dependency Treebank (PDT) corresponds to a three-layer structure annotated corpus of  Czech as a representative of inflectionally rich free-word-order languages:

  • morphological layer (lowest)- full morphological annotation
  • analytic  layer (middle) - superficial (surface) syntactic annotation using dependency treebank; level conceptually close to the syntactic annotation used in the Penn Treebank
  • tectogrammatical layer (highest) - level of linguistic meaning

  • Text Sources

    The electronic text sources have been provided by the Institute of the Czech National Corpus.The text material contains samples from the following sources:

    1. Lidové noviny (daily newspapers), 1991, 1994, 1995
    2. Mladá fronta Dnes (daily newspapers), 1992
    3. Ceskomoravský Profit (business weekly), 1994
    4. Vesmír (scientific magazine), Academia Publishers, 1992, 1993

    Inner format of PDT

    There are two internal formats employed in PDT: FS and CSTS. The former is an older format, still heavily used by some treebank tools. The latter, more general SGML-based encoding, is meant as the main PDT format (in the future, it will be followed by an XML version, probably already for PDT 2.0). See the description of the FS file format and documentation of the CSTS document type definition (csts.dtd).

    Prague Dependency Treebank version 1.0

     PDT 0.5  ("half through") has been released in 1998 and it contains 456,705 tokens (words and punctuation) in 26,610 sentences. PDT 1.0 contains about three times more tokens and sentences than PDT 0.5 (see  PDT 1.0 characteristics ) completetely manually annotated on the morphological and analytical levels and includes the preview of tectogrammatically annotated data as well.


    The Prague Dependency Treebank version 2.0 will add the tectogrammatical layer of annotation to PDT 1.0. It will be available with a reduced amount of data as preliminary "version 1.5" during 2002, and the final data volume will be reached at the end of 2004.


    The PDT 1.0  has been supported by the following grants and projects

    The PDT 2.0 will be supported by the project


    See documents about PDT here.