Directory Tree Research Articles

The average height of a node in the BANG abstract directory tree

The abstract logical data structure for the BANG file directory is a multiway tree structure with one node for each bucket in the file. Under assumptions of “perfect hashing” or “growth on data principle”, we model the growth of the tree. The average cost for search and insertion is found to be logarithmic in the file size. The order constant is small and depends on the capacity of a bucket. Simulation confirms the analytic results. Similar assumptions should be applicable to the analysis of other multi-dimensional file structures.

Experiences in providing a white pages directory service based on the X.500 standard

Abstract This paper is based on the author's experience of designing a white pages user interface to the X.500 Directory. The paper examines two issues. First, a number of problems arose during the design process which are perceived as being due to inadequacies in the 1988 protocol and service interface. In cases where these issues have been addressed in the 1992/3 standard, the proposed remedies are noted. Second, whilst access to an X.500 directory service is by protocols which have been standardised, the environment in which it runs can vary in many ways: hardware and network infrastructure; directory information tree structure; naming policies; access policies; data coverage and management; effort required for system management. However, new users of the Directory have no knowledge of this lack of uniformity, and often, quite reasonably, expect a fully populated Directory with all information accessible at high-speed. The paper suggests a range of approaches to help the directory user cope with this diversity: some of the recommendations require service agreements and coordination, whilst others have implications for user interface design.

Aesthetic layout of generalized trees

AbstractResearch on the aesthetic layout of trees has been largely concerned with the special case of binary trees with small constant‐sized nodes. Yet, without otherwise requiring the power of general graph‐layout algorithms, many layout problems involve n‐ary trees with variable‐sized nodes. This paper addresses the general issue of the aesthetic layout of such trees. Two algorithms are presented for the layout of generalized trees, and general issues, such as appropriate aesthetics, are discussed. The algorithms described are suitable for such tasks as the layout of class hierarchies, directory trees and tableau‐style proofs.

Nomenclator descriptive query optimization for large X.500 environments

Nomenclator is an architecture for providing efficient descriptive (attribute-based) naming in a large internet environment. As a test of the basic design, we have built a Nomenclator prototype that uses X.500 as its underlying data repository. X.500 SEARCH queries that previously took several minutes, can, in many cases, be answered in a matter of seconds. Our system improves descriptive query performance by trimming branches of the X.500 directory tree from the search. These tree-trimming techniques are part of an active catalog that constrains the search space as needed during query processing. The active catalog provides information about the data distribution (meta-data) to constrain query processing on demand. Nomenclator caches both data (responses to queries) and meta-data (data distribution information, tree-trimming techniques, data access techniques) to speed future queries. Nomenclator relieves users of the need to understand the structure of the name space to locate objects quickly in a large, structured name environment. Nomenclator is a meta-level service that will eventually incorporate other name services in addition to X.500. Its techniques for improving performance should be generally applicable to other naming systems. hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh Research supported in part by an AT&T Ph.D. Scholarship, National Science Foundation grants CCR8703373 and CCR-8815928, Office of Naval Research grant N00014-89-J-1222, and a Digital Equipment Corporation External Research Grant.

Structure of a directory space: a case study with a UNIX operating system

The subjects of this study are the structure of directory spaces and users' search behaviors in a UNIX operating system environment. Protocol analyses, questionnaires and surveys were conducted with users of the CAD-VAX and SPICE-VAX computers in the Architecture and Computer Science departments at Carnegie Mellon University. Findings indicate that most directories studied were organized hierarchically (tree structure) but with few levels. Some nodes were specialized as file storage areas (the leaves of the tree) and others as switch nodes that were used primarily during search. Depth first search characterized both the organization of the directories and the behavior of the users. Single-step as opposed to multiple-step traversal of the directory tree was also prevalent. Recommendations for system friendliness in terms of reusability, orientation, robustness, and consistency are discussed.

Liver biopsy: techniques, clinical applications, and complications.

<h3>Abstract</h3> We have developed pISA-tree, a straightforward and flexible data management solution for organisation of life science project-associated research data and metadata. It enables <i>on-the-fly</i> creation of enriched directory tree structure (project/Investigation/Study/Assay) via a series of sequential batch files in a standardised manner based on the ISA metadata framework. The system supports reproducible research and is in accordance with the Open Science initiative and FAIR principles. Compared with similar frameworks, it does not require any systems administration and maintenance as it can be run on a personal computer or network drive. It is complemented with two R packages, <i>pisar</i> and <i>seekr</i>, where the former facilitates integration of the pISA-tree datasets into bioinformatic pipelines and the latter enables synchronisation with the FAIRDOMHub public repository using the SEEK API. Source code and detailed documentation of pISA-tree and its supporting R packages are available from https://github.com/NIB-SI/pISA-tree.