It is widely recognized that the proliferation of annotation schemes runs counter to the need to re-use language resources , and that standards for linguistic annotation are becoming increasingly mandatory . To answer this need , we have developed a representation framework comprised of an abstract model for a variety of different annotation types ( e.g. , morpho-syntactic tagging , syntactic annotation , co-reference annotation , etc . ) , which can be instantiated in different ways depending on the annotator s approach and goals . In this paper we provide an overview of our representation framework and demonstrate its applicability to syntactic annotation . We show how the framework can contribute to comparative evaluation and merging of parser output and diverse syntactic annotation schemes . It is widely recognized that the proliferation of annotation schemes runs counter to the need to re-use language resources , and that standards for linguistic annotation are becoming increasingly mandatory . In particular , there is a need for a general framework for linguistic annotation that is flexible and extensible enough to accommodate different annotation types and different theoretical and practical approaches , while at the same time enabling their representation in a pivot format that can serve as the basis for comparative evaluation of parser output , such as PARSEVAL ( Harrison , et al . , 1991 ) , as well as the development of reusable editing and processing tools . To answer this need , we have developed a representation framework comprised of an abstract model for a variety of different annotation types ( e.g. , morpho-syntactic tagging , syntactic annotation , co-reference annotation , etc . ) , which can be instantiated in different ways depending on the annotator s approach and goals . We have implemented both the abstract model and various instantiations using XML schemas ( Thompson , et al . , 2000 ) , the Resource Definition Framework ( RDF ) ( Lassila and Swick , 2000 ) and RDF schemas ( Brickley and Guha , 2000 ) , which enable description and definition of abstract data models together with means to interpret , via the model , information encoded according to different conventions . The results have been incorporated into XCES ( Ide , et al . , 2000a ) , part of the EAGLES Guidelines developed by the Expert Advisory Group on Language Engineering Standards ( EAGLES ) 1 . The XCES provides a ready-made , standard encoding format together with a data architecture designed specifically for linguistically annotated corpora . In this paper we provide an overview of our representation framework and demonstrate its applicability to syntactic annotation . The framework has been applied to the representation of terminology ( Terminological Markup Framework2 , ISO project n.16642 ) and computational lexicons ( Ide , et al . , 2000b ) , thus demonstrating its general applicability for a variety of linguistic annotation types . We also show how the framework can contribute to comparison and merging of diverse syntactic annotation schemes . The XCES framework for linguistic annotation is built around some relatively straightforward ideas : separation of information conveyed by means of structure and information conveyed directly by specification of content categories ; development of an abstract format that puts a layer of abstraction between site-specific annotation schemes and standard specifications ; and creation of a Data Category Registry to provide a reference set of annotation categories . The emergence of XML and related standards such as RDF provides the enabling technology . We are , therefore , at a point where the creation and use of annotated data and concerns about the way it is represented can be treated separately that is , researchers can focus on the question of what to encode , independent of the question of how to encode it . The end result should be greater coherence , consistency , and ease of use and access for annotated data .

Challenge: The proliferation of annotation schemes calls for a need for flexible and extensive general annotation schemes which can accommodate different annotation types and approaches.
Approach: They propose a representation framework with an abstract model for different annotation types which can be instantiated in different ways depending on needs.
Outcome: They apply the proposed framework to representations of terminology and computational lexicons and show its applicability and how it can compare and merge annotation schemes.