Implementation of a geometric hashing technique and it\u27s application to 3D molecular structure search

This paper proposes the application of a geometric hash technique to the searching of 3D chemical structures. Chemical structures are represented in global XYZ coordinate format. An algorithm is applied to the substructures within the existing chemical structures to hash them into hash tables on disk. A query substructure is then hashed to find matches (hits) of the existing hash tables. The entries in the matching hash tables are compared to the query substructure to find the existing substructures that are an approximate match. The result is a technique which allows existing substructures to be compared to a (new) query substructure and matches found in the case of rotation, atom insertion/deletion, and small differences in precision of the XYZ coordinates

Query processing of geometric objects with free form boundarie sin spatial databases

The increasing demand for the use of database systems as an integrating factor in CAD/CAM applications has necessitated the development of database systems with appropriate modelling and retrieval capabilities. One essential problem is the treatment of geometric data which has led to the development of spatial databases. Unfortunately, most proposals only deal with simple geometric objects like multidimensional points and rectangles. On the other hand, there has been a rapid development in the field of representing geometric objects with free form curves or surfaces, initiated by engineering applications such as mechanical engineering, aviation or astronautics. Therefore, we propose a concept for the realization of spatial retrieval operations on geometric objects with free form boundaries, such as B-spline or Bezier curves, which can easily be integrated in a database management system. The key concept is the encapsulation of geometric operations in a so-called query processor. First, this enables the definition of an interface allowing the integration into the data model and the definition of the query language of a database system for complex objects. Second, the approach allows the use of an arbitrary representation of the geometric objects. After a short description of the query processor, we propose some representations for free form objects determined by B-spline or Bezier curves. The goal of efficient query processing in a database environment is achieved using a combination of decomposition techniques and spatial access methods. Finally, we present some experimental results indicating that the performance of decomposition techniques is clearly superior to traditional query processing strategies for geometric objects with free form boundaries