9500647
Querying Multimedia Data from Multiple Repositories by Content: the Garlic Project
We describe Garlic, an object-oriented multimedia middleware query system. Garlic enables existing data management components, such as a relational database or a full text search engine, to be integrated into an extensible information management system that presents a common interface and user access tools. We focus in this paper on how QBIC, an image retrieval system that provides content-based image queries, can be integrated into Garlic. This results in a system in which a single query can combine visual and nonvisual data using type-specific search techniques, enabling a new breed of multimedia applications
5949420
Indexing Alternatives for Multiversion Locking
In this paper, we present several options for extending single-version indexing schemes for use with multiversion two-phase locking. The proposed options are orthogonal to the underlying indexing structure (e.g., hashing or B+ trees). The options differ in where they place references to individual versions; this version selection information is placed either with the data or in the leaf entries of one or more indices. We also briefly summarize the results of a performance study showing that storing version selection information with the data is usually the best option because it keeps indices smaller, thus enabling a larger fraction of the indices to remain cached in the buffer pool.
1009208
Fine-grained sharing in a page server OODBMS
For reasons of simplicity and communication efficiency, a number of existing object-oriented database management systems are based on page server architectures; data pages are their minimum unit of transfer and client caching. Despite their efficiency, page servers are often criticized as being too restrictive when it comes to concurrency, as existing systems use pages as the minimum locking unit as well. In this paper we show how to support object-level locking in a page server context. Several approaches are described, including an adaptive granularity approach that uses page-level locking for most pages but switches to object-level locking when finer-grained sharing is demanded. We study the performance of these approaches, comparing them to both a pure page server and a pure object server. For the range of workloads that we have examined, our results indicate that a page server is clearly preferable to an object server. Moreover, the adaptive page server is shown to provide very good performance, generally outperforming the pure page server, the pure object server, and the other alternatives as well.
16172316
Extending SQL-92 for OODB access: design and implementation experience
This paper describes the design and implementation of a query engine that provides extended SQL-based access to the data managed by an object-oriented database system. This query engine allows extended SQL queries to be embedded in C++ programs or issued interactively as from a command line interface. The language supported by the engine is the complete SQL-92 select statement plus object extensions for navigating along paths and embedded structures, querying nested sets, and invoking member functions. In addition, an object-oriented SQL view facility is provided. Using this view facility, one can define object-oriented views; one can also define views that flatten complex OODB schemas, allowing direct access by existing tools designed to provide remote access to relational databases. The view facility also supports the definition of views that include reference and set-valued columns based on other views, thus allowing entire "view schemas" to be created. This paper describes the SQL-92 query and view extensions and discusses a number of issues that arose on the way to the implementation that is currently running on top of the ObjectStore OODB system.
6255878
Towards heterogeneous multimedia information systems: the Garlic approach
Provides an overview of the Garlic project, a new project at the IBM Almaden Research Center. The goal of this project is to develop a system and associated tools for the management of large quantities of heterogeneous multimedia information. Garlic permits traditional and multimedia data to he stored in a variety of existing data repositories, including databases, files, text managers, image managers, video servers, and so on; the data is seen through a unified schema expressed in an object-oriented data model and can be queried and manipulated using an object-oriented dialect of SQL, perhaps through an advanced query/browser tool that we are also developing. The Garlic architecture is designed to be extensible to new kinds of data repositories, and access efficiency is addressed via a "middleware" query processor that uses database query optimization techniques to exploit the native associative search capabilities of the underlying data repositories.<<ETX>>
7665858
Shoring up persistent applications
SHORE (Scalable Heterogeneous Object REpository) is a persistent object system under development at the University of Wisconsin. SHORE represents a merger of object-oriented database and file system technologies. In this paper we give the goals and motivation for SHORE, and describe how SHORE provides features of both technologies. We also describe some novel aspects of the SHORE architecture, including a symmetric peer-to-peer server architecture, server customization through an extensible value-added server facility, and support for scalability on multiprocessor systems. An initial version of SHORE is already operational, and we expect a release of Version 1 in mid-1994.
16894136
Query processing in main memory database management systems
Most previous work in the area of main memory database systems has focused on the problem of developing query processing techniques that work well with a very large buffer pool. In this paper, we address query processing issues for memory resident relational databases, an environment with a very different set of costs and priorities. We present an architecture for a main memory DBMS, discussing the ways in which a memory resident database differs from a disk-based database. We then address the problem of processing relational queries in this architecture, considering alternative algorithms for selection, projection, and join operations and studying their performance. We show that a new index structure, the T Tree, works well for selection and join processing in memory resident databases. We also show that hashing methods work well for processing projections and joins, and that an old join method, sort-merge, still has a place in main memory.
28682270
Extending and solving a multiperiod congested network flow model
Abstract We consider an existing model for optimizing time-varying flows on a congested network, and extend it so as to improve its accuracy while reducing computation. The model has been developed in a series of articles and has a variety of applications. Solving the model is a significant problem, since it is a non-linear program and can be very large for even small or medium size applications. Hitherto the model has been solved by taking a piecewise linear approximation and solving this as a linear program, perhaps taking advantage of the staircase structure of the constraints. However, this staircase is not available in the extended model. Further, the existing solution methods do not take advantage of the network structure of the problem. Here we show that a piecewise linear version of the model can be stated as a pure processing network (PPN); this allows algorithms for PPNs to be used to solve the model. We also propose a penalty (or barrier) function solution method. This reduces the problem to successively reoptimizing a program equivalent to the well-known static traffic assignment model. The latter is a convex cost, linearly constrained, un capacitated network flow problem. The above solution methods apply both to the basic model and the extended model.
2593477
A Study of Index Structures for a Main Memory Database Management System
One approach to achieving high performance in a database management system is to store the database in main memorv rather than on disk. -One can then design new data structures aid algorithms oriented towards making eflicient use of CPU cycles and memory space rather than minimizing disk accesses and &ing disk space efliciently. In this paper we present some results on index structures from an ongoing study of main memory database management systems. We propose a new index structure, the T Tree, and we compare it to existing index structures in a main memory database environment. Our results indicate that the T Tree provides good overall performance in main memory.
6780360
An exit-flow model used in dynamic traffic assignment
We consider the behaviour of a link exit-flow model that has been used to model link flows in dynamic traffic assignment (DTA) on networks. In particular, we investigate how the model behaves when time and space (the link length) discretised and the discretisation is varied. We present numerical examples based on various inflow patterns and exit-flow functions and draw conclusions for applications of the model in discrete space and in discrete or continuous time. If inflows are always less than capacity and the link is homogeneous, with no obstructions at the exit, then if the discretisation is refined to the continuous limit the model goes to the solution of the well-known LWR model. However, we observe, somewhat counter intuitively, that the usual continuous-time model does not give as good an approximation to the LWR solution as does the discrete-time model: for a best approximation, the discretisation of space and time should be synchronised. We also investigate the 'dip' in outflows, or 'jamming' of outflows, that the model display, if inflows are permitted to exceed a capacity limit (as they sometimes do in published applications of the model) and the exit-flow function has a downward sloping part (which has usually been assumed away in DTA applications). In that case, if the number of spatial segments is increased, or the number of time intervals is reduced, then any dip in outflows occurs sooner and is more pronounced, and leads to earlier jamming. In the continuous limit, the jam occurs at the link entrance, preventing inflows in excess of capacity.