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- Tomás Skopal
- EDBT
- 2006

The retrieval of objects from a multimedia database employs a measure which defines a similarity score for every pair of objects. The measure should effectively follow the nature of similarity, hence, it should not be limited by the triangular inequality, regarded as a restriction in similarity modeling. On the other hand, the retrieval should be as… (More)

- Tomás Skopal
- ACM Trans. Database Syst.
- 2007

In multimedia systems we usually need to retrieve database (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… (More)

- Tomás Skopal, Jaroslav Pokorný, Václav Snásel
- ADBIS
- 2004

In this paper we introduce the Pivoting M-tree (PM-tree), a metric access method combining M-tree with the pivot-based approach. While in M-tree a metric region is represented by a hyper-sphere, in PM-tree the shape of a metric region is determined by intersection of the hyper-sphere and a set of hyper-rings. The set of hyper-rings for each metric region is… (More)

- Tomás Skopal, Benjamin Bustos
- ACM Comput. Surv.
- 2011

The task of similarity search is widely used in various areas of computing, including multimedia databases, data mining, bioinformatics, social networks, etc. In fact, retrieval of semantically unstructured data entities requires a form of aggregated qualification that selects entities relevant to a query. A popular type of such a mechanism is similarity… (More)

- Benjamin Bustos, Tomás Skopal
- Multimedia Information Retrieval
- 2006

An important research issue in multimedia databases is the retrieval of similar objects. For most applications in multi-media databases, an exact search is not meaningful. Thus, much effort has been devoted to develop efficient and effective similarity search techniques. A recent approach, that has been shown to improve the effectiveness of similarity… (More)

- Tomás Skopal, Jaroslav Pokorný, Václav Snásel
- DASFAA
- 2005

We introduce a method of searching the k nearest neighbours (k-NN) using PM-tree. The PM-tree is a metric access method for similarity search in large multimedia databases. As an extension of M-tree, the structure of PM-tree exploits local dynamic pivots (like M-tree does it) as well as global static pivots (used by LAESA-like methods). While in M-tree a… (More)

- Tomás Skopal, David Hoksza
- ADBIS
- 2007

The M-tree and its variants have been proved to provide an efficient similarity search in database environments. In order to further improve their performance, in this paper we propose an extension of the M-tree family, which makes use of nearest-neighbor (NN) graphs. Each tree node maintains its own NN-graph, a structure that stores for each node entry a… (More)

- Tomás Skopal, Jaroslav Pokorný, Michal Krátký, Václav Snásel
- ADBIS
- 2003

The M-tree is a dynamic data structure designed to index metric datasets. In this paper we introduce two dynamic techniques of building the M-tree. The first one incorporates a multi-way object insertion while the second one exploits the generalized slim-down algorithm. Usage of these techniques or even combination of them significantly increases the… (More)

- Jakub Lokoc, Magnus Lie Hetland, Tomás Skopal, Christian Beecks
- SISAP
- 2011

The <i>signature quadratic form distance</i> has been introduced as an adaptive similarity measure coping with flexible content representations of multimedia data. While this distance has shown high retrieval quality, its high computational complexity underscores the need for efficient search methods. Recent research has shown that a huge improvement in… (More)

- Tomás Skopal, Michal Krátký, Jaroslav Pokorný, Václav Snásel
- Inf. Syst.
- 2006

In multi-dimensional databases the essential tool for accessing data is the range query (or window query). In this paper we introduce a new algorithm of processing range query in universal B-tree (UB-tree), which is an index structure for searching in multi-dimensional databases. The new range query algorithm (called the DRU algorithm) works efficiently,… (More)