Abstract
In multimedia systems we usually need to retrieve DB objects based on their similarity to a query object, while the similarity assessment is provided by a measure which defines a (dis)similarity score for every pair of DB objects. In most existing applications, the similarity measure is required to be a metric, where the triangle inequality is utilized to speedup the search for relevant objects by use of metric access methods (MAMs), e.g. the M-tree.
A recent research has shown, however, that non-metric measures are more appropriate for similarity modeling due to their robustness and ease to model a made-to-measure similarity. Unfortunately, due to the lack of triangle inequality, the non-metric measures cannot be directly utilized by MAMs.
From another point of view, some sophisticated similarity measures could be available in a black-box non-analytic form (e.g. as an algorithm or even a hardware device), where no information about their topological properties is provided, so we have to consider them