A posting from Kiril Simov of the BulTreeBank Project announces the Version 2.0 release of CLaRK, an XML-based System for Corpora Development. The principal aim of the CLaRK system design is minimization of human intervention during the creation of language resources. It incorporates several XML-based technologies, including a Unicode XML Editor, XPath Engine, XSLT Engine, XML Constraints, and XML Cascaded Regular Grammar Engine. The basic mechanism of CLaRK for linguistic processing of text corpora is the cascaded regular grammar processor. The main challenge to the grammars in question is how to apply them on XML encoding of the linguistic information. The system offers a solution using an XPath language for constructing the input word to the grammar and an XML encoding of the categories of the recognised words. Several mechanisms for imposing constraints over XML documents are available. The constraints cannot be stated by the standard XML technology. The following types of constraints are implemented in CLaRK: (1) Regular expression constraints: additional constraints over the content of given elements based on a context; (2) Number restriction constraints: cardinality constraints over the content of a document; (3) Value constraints: restriction of the possible content or parent of an element in a document based on a context." The CLaRK system is implemented in Java and is available for download.

Uses of the CLaRK System

• Corpora markup. Users work with the XML tools of the system in order to mark-up texts with respect to an XML DTD. This task usually requires an enormous human effort and comprises both the mark-up itself and its validation afterwards. Using the available grammar resources such as morphological analyzers or partial parsing, the system can state local constraints reflecting the characteristics of a particular kind of texts or mark-up. One example of such constraints can be as follows: a PP according to a DTD can have as parent an NP or VP, but if the left sister is a VP then the only possible parent is VP. The system can use such kind of constraints in order to support the user and minimize his work.

• Dictionary compilation for human users. The system will support the creation of the actual lexical entries whose structure will be defined via an appropriate DTD. The XML tools will be used also for corpus investigation that provides appropriate examples of the word usage in the available corpora. The constraints incorporated in the system will be used for writing a grammar of the sublanguages of the definitions of the lexical items, for imposing constraints over elements of lexical entries and the dictionary as a whole.

• Corpora investigation. The CLaRK System offers a rich set of tools for searching over tokens and mark-up in XML corpora, including cascaded grammars, XPath language. Their combinations are used for tasks such as: extraction of elements from a corpus - for example, extraction of all NPs in the corpus; concordance - for example, give me all NPs in the context of their use ordered by a user defined set of criteria. [see the project web page]