Multisource web news portals provide various advantages such as richness in news content and an opportunity to follow developments from different perspectives. However, in such environments, news variety and quantity can have an overwhelming effect. New-event detection and topic-tracking studies address this problem. They examine news streams and organize stories according to their events; however, several tracking stories of an event/topic may contain no new information (i.e., no novelty). We study the novelty detection (ND) problem on the tracking news of a particular topic. For this purpose, we build a Turkish ND test collection called BilNov-2005 and propose the usage of three ND methods: a cosine-similarity (CS)-based method, a language-model (LM)-based method, and a cover-coefficient (CC)-based method. For the LM-based ND method, we show that a simpler smoothing approach, Dirichlet smoothing, can have similar performance to a more complex smoothing approach, Shrinkage smoothing. We introduce a baseline that shows the performance of a system with random novelty decisions. In addition, a category-based threshold learning method is used for the first time in ND literature. The experimental results show that the LM-based ND method significantly outperforms the CS-and CC-based methods, and categorybased threshold learning achieves promising results when compared to general threshold learning.
IntroductionThe Internet has changed the news industry (The Economist, 2011). Most newspapers and news agencies provide news on their web pages. News portals work as a news aggregator and gather, merge, and organize news articles obtained from various sources. Multisource news portals provide various advantages such as richness in news content and an opportunity to follow event developments from different perspectives. In addition, it is practical to Received May 20, 2011; revised September 12, 2011; accepted September 28, 2011 1 Present address: Computer Science Department, New Jersey Institute of Technology, University Heights Newark, NJ 07102.© 2011 ASIS&T • Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/asi.21697 follow different news sources from a single web page. Google News (http://news.google.com) is a well-known commercial news portal example. It offers many services such as information retrieval, personalized information filtering, and news clustering. Research-oriented examples include NewsBlaster (McKeown et al., 2002) and NewsInEssence (Radev, Otterbacher, Winkel, & Blair-Goldensohn, 2005), each of which provides clustering and summarization services over the news.As the number of sources and events increase, news readers may be overloaded with information and thus may face difficulty in finding news related to their interests. Different organizational techniques have been employed for more effective, efficient, and enjoyable browsing. Studies on new-event detection and topic tracking aim to organize news with respect to events or topics. In topic detection and trackin...