<?xml version="1.0" standalone="yes"?>
<Paper uid="N03-3008">
  <Title>Investigations on Event Evolution in TDT</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> A fairly novel area of retrieval called topic detection and tracking (TDT) attempts to design methods to automatically (1) spot new, previously unreported events, and (2) follow the progress of the previously spotted events (Allan et al., 1998c; Yang et al., 1998).</Paragraph>
    <Paragraph position="1"> Our contribution deals with three problems in TDT.</Paragraph>
    <Paragraph position="2"> Firstly, we present a new definition for a topic that would model the event evolution, i.e., the changing nature of a topic. The previous event definitions do not really lend themselves to this change. Secondly, we investigate an approach suggested by Makkonen, Ahonen-Myka and Salmenkivi (2002). They partitioned the termspace into four semantic classes and represented each class with a designated vector. Unlike the term-weighting model of Yang et al. (2002) this approach enables the use of introduction of different similarity measures for each semantic class. We formalize the comparison method and suggest a a0 NN approach based on this formalization. Thirdly, we suggest the use of dynamic hierarchies in a TDT system that would decrease the exhaustive computation of the first story detection. In practice this means that we import text categorization on top of TDT. The purpose of this paper is to outline the main aspects of our ongoing and future work. As this is mainly work-in-progress, we do not have empirical motivation for our work.</Paragraph>
    <Paragraph position="3"> This paper is organized as follows: We will discuss the problems of TDT in Section 2 In Section 3 we examine the definitions of an event and a topic. Section 4 presents a novel event representation and an approach to measure the similarity of such elements. In Section 5 we deal with dynamic hierarchies. In Section 6 we discuss our conclusions. null</Paragraph>
  </Section>
class="xml-element"></Paper>