Using Text and Image Retrieval Systems. Lic2m experiments at ImageCLEF 2006

In the ImageCLEF 2006 campaign, the LIC2M participated in the imageclefphoto ad hoc task. We perform experiments on merging the results of two independent search systems: a cross-language information retrieval system exploiting the text part of the query and a content-based image retrieval system exploiting the example images given with the query. The merging is performed a posteriori using a weighted sum of the scores given by each system. This kind of merging can improve the results, but gain in the submitted runs remains quite small, comparatively to our experiments of last campaigns. This is due to the relatively poor results of the CBIR part. A first analysis give some hints on possible improvements: example images are often chosen to be visually different to show several aspects of possible relevant images for the chosen topic, therefore the merge of CBIR results for each example image can be irrelevant. However, using only one example image (provided we can choose the best one), or using CBIR results for each example image, but only in correspondence with text results can improve the results.