8323337
Modeling Functional Data Sources as Relations
In this paper we present a model of functional access to data that, we argue, is suitable for modeling a class of data repositories characterized by functional access, such as web sites. We discuss the problem of modeling such data sources as a set of relations, of determining whether a given query expressed on these relations can be translated into a combination of functions defined by the data sources, and of finding an optimal plan to do so.
7447998
Semiorder database for complex activity recognition in multi-sensory environments
A prototype semiorder database used for activity recognition in multi-sensory monitoring environments is described. Activities are spatio-temporal compositions of events, which are a type of atomic semantic units for such compositions. The focus is on the temporal composition of activities from events in the presence of bounded duration of temporal uncertainty in an event occurrence. Such temporal uncertainty forces the concurrency between event occurrences to be intransitive. Under certain assumptions, a subclass of partial orders, known as semiorders, models such intransitive concurrency appropriately. The semiorder database stores events and their semiorder temporal order of occurrences. A semiorder data model and the corresponding query language that embeds a semiorder pattern language are the main constituents of the semiorder database. We demonstrate this database and queries for activity recognition in a real time environment. The demonstration also includes a transducer subsystem for detection of events.
19099120
An Extended Object-Oriented Data Model for Large Image Bases
This paper presents an object-oriented data model for an image database. The formal presentation of the model stems from an analysis of the domain of remotely sensed radar images of the Arctic ice. The data model maintains the distinction between generic spatial attributes and representation dependent spatial attributes. This results in a four-layer network of objects, attributes, relations, events and representations. In the representation level, the data model is very close to a functional data model. The model serves as the formal foundation of the VIMSYS (Visual Information Management SYStem) project, which aims to perform content and similarity based query processing of large image repositories.
18656965
Integrating GIS and Imagery Through XML-Based Information Mediation
In this paper, we investigate a mediation-based approach to integrating information from geospatial information sources such as GIS's and databases of geo-referenced imagery. This approach is based on the use of XML to represent the information at the sources, by exporting XML Document Type Definitions (DTD's) associated with each source, and employing XML-based query languages to query integrated views of information at the mediator. Our goal is to enable users to issue a single query to the mediator, and provide the capability to return a result that seamlessly combines information from multiple sources. This paper describes issues in designing such a mediated system for geospatial data. Our notion of mediation for geospatial data is the "logical integration" of data achieved by creating correspondences between related spatial information, similar to the way mediation is done in "standard" databases. Thus, this notion of mediation does not depend on the development of spatial algorithms that operate on images or vector data and achieve "physical integration" through techniques such as image conflation. However, the mediator architecture does allow for the integration of physical integration techniques. The paper discusses issues related to wrapping of GIS and other geospatial sources and issues in querying such sources using an XML-based query language.
17115672
Emergent Semantics through Interaction in Image Databases
In this paper, we briefly discuss some aspects of image semantics and the role that it plays for the design of image databases. We argue that images don't have an intrinsic meaning, but that they are endowed with a meaning by placing them in the context of other images and by the user interaction. From this observation, we conclude that, in an image, database users should be allowed to manipulate not only the individual images, but also the relation between them. We present an interface model based on the manipulation of configurations of images.
10822035
An extensible information model for shared scientific data collections
An information model is defined to support sharing of composite-media scientific data. The model consists of data objects and links. Data objects are associated with descriptorswhich contain all the metadata related to the object. A novel aspect of the information model is that both the data and metadata associated with a data object can be in structured or semistructured form. The links in the model are typed, and contain several built-in types such as resolution and derivation link types, to adequately model object relationships in scientific data. The model is extensible in the sense that users are allowed to define new object types and new link types. At the San Diego Supercomputer Center, we are currently investigating issues in providing the necessary infrastructure to implement this model. ©1999 Elsevier Science B.V. All rights reserved.
42435460
Embeddings of k-connected graphs of pathwidth k
We present O(n^3) embedding algorithms (subgraph isomorphism and its generalizations) for classes of graphs of bounded pathwidth, where n is the number of vertices in the graph. These include the first polynomial-time algorithm for minor containment and the first O(n^c) algorithm (c a constant independent of k) for topological embedding of graphs from subclasses of partial k-trees, as well as an O(n^2) algorithm for subgraph isomorphism. Of independent interest are structural properties of k-connected graphs of bounded pathwidth on which our algorithms are based. We also describe special cases which reduce to various generalizations of string matching, permitting more efficient solutions. Finally, we describe n^k^+^O^(^1^) algorithms for solving these problems on arbitrary graphs of pathwidth at most k.
14070074
Stream processing of XPath queries with predicates
We consider the problem of evaluating large numbers of XPath filters, each with many predicates, on a stream of XML documents. The solution we propose is to lazily construct a single deterministic pushdown automata, called the XPush Machine from the given XPath fllters. We describe a number of optimization techniques to make the lazy XPush machine more efficient, both in terms of space and time. The combination of these optimizations results in high, sustained throughput. For example, if the total number of atomic predicates in the filters is up to 200000, then the throughput is at least 0.5 MB/sec: it increases to 4.5 MB/sec when each fllter contains a single predicate.
19362396
Finding Largest Common Embeddable Subtrees
We consider the problem of determining the largest tree embeddable in two labeled trees T and T′, where the embedding relation is one of subgraph isomorphism or topological embedding. This problem is a generalization of classical tree pattern matching where the problem is to determine if one labeled tree is isomorphic to a subgraph of another. In this paper, we present a general framework for the variations on the problem, for the two embedding relations and for different assumptions about labeling of nodes in the trees. Our general paradigm provides sequential and parallel algorithms for the various subproblems, many of which have no other known solutions.
1412337
Simpler and better approximation algorithms for network design
We give simple and easy-to-analyze randomized approximation algorithms for several well-studied NP-hard network design problems. Our algorithms improve over the previously best known approximation ratios. Our main results are the following.We give a randomized 3.55-approximation algorithm for the connected facility location problem. The algorithm requires three lines to state, one page to analyze, and improves the best-known performance guarantee for the problem.We give a 5.55-approximation algorithm for virtual private network design. Previously, constant-factor approximation algorithms were known only for special cases of this problem.We give a simple constant-factor approximation algorithm for the single-sink buy-at-bulk network design problem. Our performance guarantee improves over what was previously known, and is an order of magnitude improvement over previous combinatorial approximation algorithms for the problem.
17407466
Point-Based Approaches to Qualitative Temporal Reasoning
We are interested in the problem of qualitative, point-based temporal reasoning. That is, given a set of assertions concerning the relative positions of points in time, we are interested in compiling the assertions into a representation that supports efficient reasoning, determining consistency, computing the strongest entailed relation between any two points and updating the set of assertions. We begin by considering a general set of operations and their corresponding algorithms, applicable to general point-based temporal domains. We also consider special-purpose reasoners, which may be expected to perform well in an application domain with a restricted structure. Lastly we consider reasoners which incorporate restricted structures into a more general reasoning framework. Finally, we present instances of each such approach and give a comparison of their performance on random data sets.