Extendible Array Research Articles

Segment Oriented Compression Scheme for MOLAP Based on Extendible Multidimensional Arrays

Many statistical and MOLAP applications use multidimensional arrays as the basic data structure to allow the efficient and convenient storage and retrieval of large volumes of business data for decision making. Allocation of data or data compression is a key performance factor for this purpose because performance strongly depends on the amount of storage required and availability of memory. This holds especially for data warehousing environments in which huge amounts of data have to be dealt with. The most evident consequence of data compression is that it reduces storage cost by packing more logical data per unit of physical capacity. And improved performance is a net outcome because less physical data need to be retrieved during scan-oriented queries. In this paper, an efficient data compression technique is proposed based on the notion of extendible array. The main idea of the scheme is to compress each of the segments of the extendible array using the position information only. We compare the proposed scheme for different performance issues with prominent compression schemes.

An Efficient Encoding Scheme to Handle the Address Space Overflow for Large Multidimensional Arrays

We present a new implementation scheme of multidimensional array for handling large scale high dimensional datasets that grows incrementally. The scheme implements a dynamic multidimensional extendible array employing a set of two dimensional extendible arrays. The multidimensional arrays provide many advantages but it has some problems as well. The Traditional Multidimensional array is not dynamic extendible. Again, if the length of dimension and number of dimension of a multidimensional array is large then the address space for the array overflows quickly. In this paper, we propose a solution against the essential problem of address space overflow for handling large scale multidimensional datasets using our implementation model. We also propose a record encoding scheme based on our model for representing relational tables using multidimensional array. We evaluate our proposed scheme by comparing with Traditional Multidimensional Array (TMA) for different operations and find a reasonable delay of address space overflow with no retrieval penalty. We also compare the encoded scheme with traditional scheme and find that proposed encoded scheme performs better on range retrieval for sparse array.

A New Parallel Data Cube Construction Scheme

The pre-computation of data cubes is critical for improving the response time of OLAP (On-Line Analytical Processing) systems. To meet the need for improved performance created by growing data sizes, parallel solutions for data cube construction are becoming increasingly important. This paper presents a new parallel data cube construction scheme based on an extendible multidimensional array, which is dynamically extendible along any dimension without relocating any existing data. The authors have implemented and evaluated their parallel data cube construction methods on shared-memory multiprocessors. Given the performance limit, the methods achieve close to linear speedup with load balance. The authors’ experiments also indicate that their parallel methods can be more scalable on higher dimensional data cube construction.

A Labeling Scheme for Dynamic XML Trees Based on History-offset Encoding

This paper presents a novel labeling scheme for dynamic XML trees. The scheme employs history-offset encoding method for multidimensional datasets and takes advantage of this method by embedding an XML tree into a multidimensional extendible array. Even if structural updates are made on the XML tree, no relabeling of nodes is required under the support of extra data structure for preserving the document order. The most significant advantage of our scheme over other existing labeling schemes is that the storage cost for generated labels is very small irrespective of the order and the position of node insertions; in most of our competing schemes, the generated label size would become very large if the insertions occur around the same position. After describing our labeling scheme, label size, total label storage cost and node access performance are examined compared with other sophisticated schemes, such as ORDPATH, QED, DLN and Prime Numbering, and proves that our scheme outperforms these schemes in some criteria.

An Incremental Maintenance Scheme of Data Cubes and Its Evaluation

Data cube construction is a commonly used operation in data warehouses. Since both the volume of data stored and analyzed in a data warehouse and the amount of computation involved in data cube construction are very large, incremental maintenance of data cube is really effective. In this paper, we employ an extendible multidimensional array model to maintain data cubes. Such an array enables incremental cube maintenance without relocating any data dumped at an earlier time, while computing the data cube efficiently by utilizing the fast random accessing capability of arrays. In this paper, we first present our data cube scheme and related maintenance methods, and then present the corresponding physical implementation scheme. We developed a prototype system based on the physical implementation scheme and performed evaluation experiments based on the prototype system.

A Parallel Implementation Scheme of Relational Tables Based on Multidimensional Extendible Array

In this article, an efficient parallel implementation scheme of relational tables is proposed and evaluated. The scheme implements a relational table by employing an extendible multidimensional array. Data allocation is a key performance factor for parallel database systems. This holds especially for data warehousing environments in which huge amounts of data have to be dealt with. In our scheme, an efficient data allocation technique is used, based on the notion of extendible array. The dynamic load balancing is conducted when load on each processor is not uniformly distributed in order to maximize processor utilization.

Folded hydrophone array for narrow marine vehicles

An extendible linear sonar array for an Autonomous Underwater Vehicle (AUV) comprises a linear hydrophone array fixed in the nose of the AUV and two hydrophone array segments mounted at the leading edge of stabilization fins extendible from and retractable into the AUV. The stabilization fins are pivoted to move between extended and retracted positions where, in the extended position, the movable arrays together with the fixed nose array form a linear sonar array with extended width. In the retracted position, the stabilization fins with the hydrophone arrays pivot and fold back into stow channels in the AUV body. The stabilization fins may include movable control surfaces to control the attitude of the AUV, or the stabilization fins can be rotated when in the extended position to provide attitude control.

A storage scheme for extendible arrays

Conventional methods of storing aK-dimensional array allow easy extension only along one dimension. We present a technique of allocating a linear sequence of contiguous storage locations for aK-dimensional extendible array by adjoining blocks of (K−1)-dimensional subarrays. Element access is by determination of the block header location and then the displacement within the block. For cubical and all practical cases of rectangular arrays considered, the storage requirement isO (N) whereN is the array size. The element access cost isO (K) for the 2-step computed access function used.

Procedures for managing extendible array files

AbstractVarieties of files are reviewed and the notion of a file space is discussed. A number of properties which characterize file spaces are listed. This modest theoretical framework has a clarifying influence on the subject of files. Certain file‐system primitives are introduced which are similar to those in most commonly‐known operating systems, and then these primitives are used in constructing a collection of routines for reading and writing extedible arrays. Extendible arrays are based on fixed page size randomly‐accessible files and they are a useful universal input/output (I/O) structure for many different storage and retrieval schemes. The routines for managing such files are similar to the mechanisms used in handling a paged address space in a virtual memory system. The contribution of this paper lies in the detailed implementation which is presented; these routines are well understood in principle, but tricky to construct in practice. Finally, these routines are used in a practical example which provides for managing a variable blocksize free space list within a extendible array.

On storing concatenable arrays

Previous studies of extendible array storage mappings (esm's) have envisioned arrays as expanding via a sequence of adjunctions of rows and/or columns. Another mechanism for array expansion is the successive (row-wise or column-wise) concatenation of already stored arrays. This type of expansion is facilitated if the addresses of positions of the resultant composite arrays can be obtained easily and systematically from the addresses of positions of the constituent arrays. A property of esm's, termed translatability , is introduced and is argued intuitively to guarantee easy concatenation of stored arrays. The class of persistent two-dimensional translatable esm's is shown to be a one-parameter family of esm's whose initial member is the familiar diagnonal pairing function. The derived explicit form of these esm's permits one to argue algorithmically that they afford one easy concatenation of stored arrays.

Storage schemes for boundedly extendible arrays

The high costs of extendibility in array realizations can be reduced dramatically by placing a bound on how big the arrays of interest will grow. Whereas extendible array realizations require order of p · log p storage locations to store two-dimensional arrays having p or fewer positions, boundedly extendible array realizations (with a bound of p) can store these same arrays in precisely p locations. Moreover, boundedly extendible realizations can be designed to afford one additive traversal of both the rows and columns of the stored arrays, albeit at the cost of very inefficient storage utilization (order of p 3/2 locations are needed to store arrays having p or fewer positions); extendible array realizations cannot yield such bidirectional additive traversal, irrespective of the price one is willing to pay. Moreover, if one can specify that the smallest array of interest is of shape h × w, then the p 3/2 cost of storage utilization can be improved to roughly p · (p/hw)1/2 but no further.

On Preserving Proximity in Extendible Arrays

A. L. Rosenberg [4] has shown that fully extendible array storage schemes cannot preserve proximity of array positions in any global sense but only in a local sense. The purpose of this note is to consider two problems suggested in [4]. Our first result shows that, for any k array positions of an extendible array, there is a storage scheme which stores array elements that are “close to” the given k positions optimally “close” to each other. The “local diameter of preservation” of a storage scheme is essentially the cardinality of the smallest set of contiguous locations assigned to array positions in a “neighborhood” of a given array position. Our second result shows the nonexistence of “almost everywhere” polynomial bounds of a certain type for local diameters of preservation.

Preserving Proximity in Arrays

Efficiency of storage management in algorithms which use arrays is often enhanced if the arrays are stored in a proximity-preserving manner; that is, array positions which are close to one another in the array are stored close to one another. This paper is devoted to studying certain qualitative and quantitative questions concerning preservation of proximity by array storage schemes (or,realizations). It is shown that fully extendible array realizations cannot preserve proximity in any global sense, not even proximity along a single direction (say, along rows). They can, however, preserve proximity in certain local senses; and realizations which are optimal in various senses of local preservation are exhibited. Partially extendible array storage schemes can preserve proximity in a global way; bounds on their “diameters of preservation” are derived, and optimal schemes are exhibited.

Managing Storage for Extendible Arrays

Schemes which allocate storage for extendible arrays cannot utilize storage as efficiently as can their nonextendible counterparts. Relative to formal notions of array scheme and (extendible) array realization, a formal way of gauging efficiency of storage utilization by extendible array realizations is proposed; a lower bound of $O(p \cdot (\log p)^{d - 1} )$, where p is the array size and d the dimensionality, is derived for this measure; and an extendible allocation scheme which achieves this lower bound is exhibited. Certain seminorms on Euclidean spaces can be used to construct extendible array realizations. It is shown that for realizations so constructed, the lower bound on storage utilization efficiency is $O(p^d )$. In the opposite direction, certain restrictions on the patterns of expansions of arrays can be used to circumvent the lower bound: When arrays are constrained to expand according to some fixed finite set of patterns, then one can devise extendible realizations which (a) utilize storag...

Investigation of the Applications of Advanced Communications Satellites

An experimental communications satellite will be launched later this year to flight-test various subsystems and to investigate the applications throughout society. By agreement in 1971 between Canadian and U.S.A. agencies, Canada is responsible for designing and building the spacecraft and the U.S.A. for supplying the high-power traveling-wave tube, launch vehicle and environmental test and operational support. The investigation will (1) flight-test and evaluate a traveling-wave tube with an efficiency greater than 50% and a saturated power output of 200 W at a frequency of 12 GHz; (2) flight-test a lightweight extendible solar array with an initial power output greater than 1 kW; (3) flight-test a 3-axis stabilization system; and (4) experiment with the use of the 12- and 14-GHz bands. Almost a score of agencies, universities and hospitals will participate in this experiment.