| Abstract [eng] |
Hierarchy (hierarchical tree) is a special graphical constract that fulfils the following conditions: Absence of cycles in the structure; Any of two nods are connected only on one path; A number of edges are lesser by one unit than the number of nods. Hierarchical structures are encountered in a lot of areas of human activities. For example, in family genealogy to make a detailed picture of cognate relations among different family members, geneologists design a family tree with its stirps; in publishing to make it easier to find appropriate information in a piece of work, publishers create a table of contens with its headings and subheadings; or even human thinking proceeds on basis of hierarchical sturcture when the mind generates abstracts which are arranged in a hierarchical manner, enabling a person to remember things better (Boyle M.H., Willms J.D., 2001). Similarly, hierarchical trees are widely used in almost all fields of Computer Science, e.g. framing a operaing sistem, programers make up a file system with its file arrangements to easy the user's work with data on the computer. The object of the work is to compare two methods that allow to store hierarchical structures in DBMS, and to evaluate their characteristics by experiment. To achieve the object, the following objectives have been realized: 1. The comparison of some methods which enable to store trees in RBDVS has been made; 2. The reusable components which work on a number of different methods have been designed and implimented; 3. The experiment has been carried out. |
