External query expansion in the blogosphere

We describe the participation of the University of Amsterdam’s ILPS group in the blog track at TREC 2008. We mainly explored different ways of using external corpora to expand the original query. In the blog post retrieval task we did not succeed in improving over a simple baseline (equal weights for both the expanded and original query). Obtaining optimal weights for the original and the expanded query remains a subject of investigation. In the blog distillation task we tried to improve over our (strong) baseline using external expansion, but due to differences in the run setup, comparing these runs is hard. Compared to a simpler baseline, we see an improvement for the run using external expansion on the combination of news, Wikipedia and blog posts.