Please wait, while we are loading the content...
Please wait, while we are loading the content...
| Content Provider | ACM Digital Library |
|---|---|
| Author | Rotem, D. |
| Abstract | Access methods for multidimensional data have attracted much research interest in recent years. In general, the data structures proposed for this problem partition the database into a set of disk pages (buckets). Access to the buckets is provided by searching a directory of some type such as a tree directory or inverted index or by computation of a multiattribute hash function. Examples of the first approach are Multidimensional B-trees[Sch82], K-D-B trees[Rob81] (see also [Sam84] for a survey of these methods) whereas multiattribute hashing methods are described for example in [Rot74],[Aho79],[Riv76] and [Ram83]. In addition, there are also hybrid methods which combine hashing with a directory of some type [Ore84],[Nie84], [Fag79].In all the work mentioned above, the performance is measured in terms of the number of disk accesses made to retrieve the answer without distinguishing whether these are sequential or random. We argue that performance measurements must consider this factor in order to be realistic, especially in the single user environment. Some evidence to support this claim is given in [Sal88, pg. 22] with the IBM 3380 disk drive as an example. For this type of disk, a comparison between accessing m blocks randomly and accessing a contiguous cluster of m blocks is made. The results show that for m = 10, the random access is slower by a factor of about 8 than the clustered one whereas for m = 100 it is slower by a factor of 25.Another motivation for this work are optical disks. In this case, there is a big advantage in clustering since the access mechanism on many of these drives is equipped with an adjustable mirror which allows slight deflections of the laser beam. This means that it may be possible to read a complete cluster from a sequence of adjacent tracks beneath the head with a single random seek [Chri88].Our work is inspired by an interesting recent paper [Fal86] which proposes to organize the physical layout of a multiattribute hash file by encoding record signatures using gray code rather than simple binary code. In this way neighboring buckets contain records which differ on a single bit in their signatures. It is then proved that the records which form the answer to a partial match query will tend to be contained in a smaller number of clusters as compared with the binary arrangement. It is also shown that this idea is applicable to many other multiattribute hashing schemes with a small amount of overhead. In addition, it can improve access time to directories of grid type files, extendible hashing and file methods which employ the z-ordering [Ore84]. |
| Starting Page | 225 |
| Ending Page | 234 |
| Page Count | 10 |
| File Format | |
| ISBN | 0897913086 |
| DOI | 10.1145/73721.73744 |
| Language | English |
| Publisher | Association for Computing Machinery (ACM) |
| Publisher Date | 1989-03-29 |
| Publisher Place | New York |
| Access Restriction | Subscribed |
| Content Type | Text |
| Resource Type | Article |
National Digital Library of India (NDLI) is a virtual repository of learning resources which is not just a repository with search/browse facilities but provides a host of services for the learner community. It is sponsored and mentored by Ministry of Education, Government of India, through its National Mission on Education through Information and Communication Technology (NMEICT). Filtered and federated searching is employed to facilitate focused searching so that learners can find the right resource with least effort and in minimum time. NDLI provides user group-specific services such as Examination Preparatory for School and College students and job aspirants. Services for Researchers and general learners are also provided. NDLI is designed to hold content of any language and provides interface support for 10 most widely used Indian languages. It is built to provide support for all academic levels including researchers and life-long learners, all disciplines, all popular forms of access devices and differently-abled learners. It is designed to enable people to learn and prepare from best practices from all over the world and to facilitate researchers to perform inter-linked exploration from multiple sources. It is developed, operated and maintained from Indian Institute of Technology Kharagpur.
Learn more about this project from here.
NDLI is a conglomeration of freely available or institutionally contributed or donated or publisher managed contents. Almost all these contents are hosted and accessed from respective sources. The responsibility for authenticity, relevance, completeness, accuracy, reliability and suitability of these contents rests with the respective organization and NDLI has no responsibility or liability for these. Every effort is made to keep the NDLI portal up and running smoothly unless there are some unavoidable technical issues.
Ministry of Education, through its National Mission on Education through Information and Communication Technology (NMEICT), has sponsored and funded the National Digital Library of India (NDLI) project.
| Sl. | Authority | Responsibilities | Communication Details |
|---|---|---|---|
| 1 | Ministry of Education (GoI), Department of Higher Education |
Sanctioning Authority | https://www.education.gov.in/ict-initiatives |
| 2 | Indian Institute of Technology Kharagpur | Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project | https://www.iitkgp.ac.in |
| 3 | National Digital Library of India Office, Indian Institute of Technology Kharagpur | The administrative and infrastructural headquarters of the project | Dr. B. Sutradhar bsutra@ndl.gov.in |
| 4 | Project PI / Joint PI | Principal Investigator and Joint Principal Investigators of the project |
Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon |
| 5 | Website/Portal (Helpdesk) | Queries regarding NDLI and its services | support@ndl.gov.in |
| 6 | Contents and Copyright Issues | Queries related to content curation and copyright issues | content@ndl.gov.in |
| 7 | National Digital Library of India Club (NDLI Club) | Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach | clubsupport@ndl.gov.in |
| 8 | Digital Preservation Centre (DPC) | Assistance with digitizing and archiving copyright-free printed books | dpc@ndl.gov.in |
| 9 | IDR Setup or Support | Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops | idr@ndl.gov.in |
|
Loading...
|