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<Paper uid="P01-1040">
  <Title>A Common Framework for Syntactic Annotation</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
2 Current Practice
</SectionTitle>
    <Paragraph position="0"> At the highest level of abstraction, syntactic annotation schemes represent the following kinds of information: * Category information: labeling of components based on syntactic category (e.g., noun phrase, prepositional phrase), syntactic role (subject, object), etc.; * Dependency information: relations among components, including constituency relations, grammatical role relations, etc. For example, the annotation in Figure 1, drawn from the Penn Treebank II3 (hereafter, PTB), uses LISP-like list structures to specify constituency relations and provide syntactic category labels for constituents. Some grammatical roles (subject, object, etc.) are implicit in the structure of the encoding: for instance, the nesting of the NP the front room implies that the NP is the object of the prepositional phrase, whereas the position of the NP him following and at the same level as the VP node implies that this NP is the grammatical object. Additional processing (or human intervention) is required to render these relations explicit. Note that the PTB encoding provides some explicit information about grammatical role, in that subject is explicitly labeled (although its relation to the verb remains implicit in the structure), but most relations (e.g., object ) are left implicit. Relations among non-contiguous elements demand a special numbering mechanism to enable crossreference, as in the specification of the NP-SBJ of the embedded sentence by reference to the earlier NP-SBJ-1 node.</Paragraph>
    <Paragraph position="1"> Although they differ in the labels and in some cases the function of various nodes in the tree, most annotation schemes provide a similar constituency-based representation of relations among syntactic components (see Abeille, forthcoming, for a comprehensive survey of syntactic annotation schemes). In contrast, dependency schemes (e.g., Sleator and Temperley, 1993; Tapanainen and Jarvinen, 1997; Carroll, et al., forthcoming) do not</Paragraph>
  </Section>
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