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Hierarchical Cellular Tree
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    Hierarchical Cellular Tree (HCT)

      HCT is a dynamic, parameter independent and flexible cell (node) sized indexing structure, which is optimized to achieve as focused cells as possible using the (sub-optimum) visual and aural descriptors.

      Basic Features
    • By means of the flexible cell size property, one or minimum number of cell(s) are used to store a group of similar items, which in effect reduces the degradations caused by "crowd effect" within the HCT body.
    • During their life-time the cells are under the close surveillance of their levels in order to enhance the compactness using mitosis operations whenever necessary to rid of the dissimilar item(s) from the cell. Furthermore, for the item insertions, an optimum cell search technique (Pre-emptive) is used to find out the most suitable (similar) cell in each level.
    • HCT is also intrinsically dynamic, meaning that the cell and level parameters and primitives are subject to continuous upgrade operations to provide most reliable environment. For example a cell nucleus item is changed whenever a better candidate is available and once a new nucleus item is assigned, its owner cell in the upper level is found after a cell search instead of using the old one's owner cell. Such a dynamic internal behavior keeps the HCT body intact by preventing the potential sources of corruption.
    • By means of MST within each cell, the optimum nucleus item can be assigned whenever necessary and with no cost. Furthermore the optimum split management can be done when the mitosis operation is performed. Most important of all, MST provides a reliable compactness measure via "cell similarity" for any item instead relying on only to a single (nucleus) item.
      HCT in a Nutshell:

      • Flexible Cell Size
      • Cell Maturity Level
      • In-built Minimum Spanning Tree
      • 2 Black Boxes:
          - (Dis-) Similarity Distance Calculation
          - Compactness Feature (only for mature cells)
      • Dynamic Events:
          - Mitosis (Cell Split)
          - (Incremental) MST Construction
          - Nucleus Assignment
    HCT Browsing

    • Supports 3 types of Navigations:
        - Inter-level
        - Inter-cellular
        - Random Access
    • The user is guided at each level by the nucleus items and several hierarchic levels of summarization help the user to have a "mental picture" about the entire database.
    • Each inter-cellular trip is a "summarisation" of the database, and the level of summarisation is simply the "height" of the naviagation (i.e. the owner level)

      An HCT Browsing Example

      For complete reference download our paper
      PQ over HCT

        PQ operation over HCT is executed synchronously over two parallel processes: HCT tracer and a generic process for PSQ formation using the latest QP segment. HCT tracer is a recursive algorithm, which traces among the HCT levels in order to form a QP (Query Path) for the next PSQ update. When the time allocated for this operation is completed, this process is paused and the next PSQ retrieval result is formed and presented to the user.

        QP Formation from HCT: Starting from the top level, HCT tracer algorithm recursively traces among the levels and their cells according to the similarity of the cell nucleuses.
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Release Date: 01.03.2006
Last Update: 10.09.2013
Copyright 2013 MUVIS