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Use of XML offers a structured approach for representing information while maintaining separation of form and content. XML information retrieval is different from standard text retrieval in two aspects: the XML structure may be of interest as part of the query; and the information does not have to be text. In this paper, we describe an investigation of approaches to retrieve text and images from a large collection of XML documents, performed in the course of our participation in the INEX 2006 Ad Hoc and Multimedia tracks. We evaluate three information retrieval similarity measures: Pivoted Cosine, Okapi BM25 and Dirichlet. We show that on the INEX 2006 Ad Hoc queries Okapi BM25 is the most effective among the three similarity measures used for retrieving text only, while Dirichlet is more suitable when retrieving heterogeneous (text and image) data. [ABSTRACT FROM AUTHOR]

Two common approaches in retrieving images from a collection are retrieval by text keywords and retrieval by visual content. However, it is widely recognised that it is impossible for keywords alone to fully describe visual content. This paper reports on the participation of the RMIT University group in the INEX 2005 multimedia track, where we investigated our approach of combining evidence from a content-oriented XML retrieval system and a content-based image retrieval system using a linear combination of evidence. Our approach yielded the best overall result for the INEX 2005 Multimedia track using the standard evaluation measures. We have extended our work by varying the parameter for the linear combination of evidence, and we have also examined the performance of runs submitted by participants by using the newly proposed HiXEval evaluation metric. We show that using CBIR in conjunction with text search leads to better retrieval performance. [ABSTRACT FROM AUTHOR]