PDT 2.0 Requirements on a Query Language

Proceedings of ACL-08: HLT, pages 37–45, Columbus, Ohio, USA, June 2008. c⃝2008 Association for Computational Linguistics PDT 2.0 Requirements on a Query Language Jiří Mírovský Institute of Formal and Applied Linguistics Charles University in Prague Malostranské nám. 25, 118 00 Prague 1, Czech Republic mirovsky@ufal.mff.cuni.cz Abstract Linguistically annotated treebanks play an essential part in the modern computational linguistics. The more complex the tree- banks become, the more sophisticated tools are required for using them, namely for searching in the data. We study linguistic phenomena annotated in the Prague Depen- dency Treebank 2.0 and create a list of re- quirements these phenomena set on a search tool, especially on its query lan- guage. 1 Introduction Searching in a linguistically annotated treebank is a principal task in the modern computational lin- guistics. A search tool helps extract useful infor- mation from the treebank, in order to study the lan- guage, the annotation system or even to search for errors in the annotation. The more complex the treebank is, the more so- phisticated the search tool and its query language needs to be. The Prague Dependency Treebank 2.0 (Hajič et al. 2006) is one of the most advanced manually annotated treebanks. We study mainly the tectogrammatical layer of the Prague Depen- dency Treebank 2.0 (PDT 2.0), which is by far the most advanced and complex layer in the treebank, and show what requirements on a query language the annotated linguistic phenomena bring. We also add requirements set by lower layers of annotation. In section 1 (after this introduction) we mention related works on search languages for various types of corpora. Afterwards, we very shortly in- troduce PDT 2.0, just to give a general picture of the principles and complexion of the annotation scheme. In section 2 we study the annotation manual for the tectogrammatical layer of PDT 2.0 (t-manual, Mikulová et al. 2006) and collect linguistic phe- nomena that bring special requirements on the query language. We also study lower layers of an- notation and add their requirements. In section 3 we summarize the requirements in an extensive list of features required from a search language. We conclude in section 4. 1.1 Related Work In Lai, Bird 2004, the authors name seven linguis- tic queries they consider important representatives for checking a sufficiency of a query language power. They study several query tools and their query languages and compare them on the basis of their abilities to express these seven queries. In Bird et al. 2005, the authors use a revised set of seven key linguistic queries as a basis for forming a list of three expressive features important for lin- guistic queries. The features are: immediate prece- dence, subtree scoping and edge alignment. In Bird et al. 2006, another set of seven linguistic queries is used to show a necessity to enhance XPath (a standard query language for XML, Clark, DeRose 1999) to support linguistic queries. Cassidy 2002 studies adequacy of XQuery (a search language based on XPath, Boag et al. 1999) …

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