18149163
SMOQE: a system for providing secure access to XML
XML views have been widely used to enforce access control, support data integration, and speed up query answering. In many applications, e.g., XML security enforcement, it is prohibitively expensive to materialize and maintain a large number of views. Therefore, views are necessarily virtual. An immediate question then is how to answer queries on XML virtual views. A common approach is to rewrite a query on the view to an equivalent one on the underlying document, and evaluate the rewritten query. This is the approach used in the Secure MOdular Query Engine (SMOQE). The demo presents SMOQE, the first system to provide efficient support for answering queries over virtual and possibly recursively defined XML views. We demonstrate a set of novel techniques for the specification of views, the rewriting, evaluation and optimization of XML queries. Moreover, we provide insights into the internals of the engine by a set of visual tools.
16011778
A Uniform System for Publishing and Maintaining XML Data
XML has become the prime standard for data exchange on the Web. To exchange data residing in Databases, one needs to publish it in XML. Data publishing is often done with a predefined “schema.” The chapter proposes a new approach for schema-directed publishing of relational data in XML, based on the novel notion of attribute transformation grammars (ATGs). ATGs provide guidance on how to define views conforming to target schemas (DTDs), and automatically ensure schema conformance. The chapter also develops an incremental algorithm for maintaining XML views produced by ATGs, based on new incremental computation techniques that capitalize on the hierarchical structure of XML data and unique features of the ATGs. Taking real-life data from Gene Ontology (GO), this chapter also demonstrates how this system can efficiently publish the GO data in XML with respect to a predefined recursive DTD, and how it incrementally updates the target XML data in response to changes to the underlying GO database.
17179157
Conditional Functional Dependencies for Data Cleaning
We propose a class of constraints, referred to as conditional functional dependencies (CFDs), and study their applications in data cleaning. In contrast to traditional functional dependencies (FDs) that were developed mainly for schema design, CFDs aim at capturing the consistency of data by incorporating bindings of semantic ally related values. For CFDs we provide an inference system analogous to Armstrong's axioms for FDs, as well as consistency analysis. Since CFDs allow data bindings, a large number of individual constraints may hold on a table, complicating detection of constraint violations. We develop techniques for detecting CFD violations in SQL as well as novel techniques for checking multiple constraints in a single query. We experimentally evaluate the performance of our CFD-based methods for inconsistency detection. This not only yields a constraint theory for CFDs but is also a step toward a practical constraint-based method for improving data quality.
15745921
Wireless networks and random geometric graphs
In this paper, mobile ad-hoc networks are studied. Chen and Jia (2001) proposed a routing algorithm by utilizing multiple communication channels and localizing the routing information (routing tables) for mobile stations within the wireless network. The routing algorithm relies on a spanning tree of the underlying network. It is proven that both the construction of the spanning tree and the routing algorithm are efficient. The routing algorithm is also reliable because of the frequent update of the spanning tree which the routing scheme is based on. The underlying network is a random geometric graph G(A,n) formed on a set of uniformly randomly located points in the unit disk, in which two vertices are adjacent if and only if their Euclidean distance is at most A.
2524138
Code synthesis based on object-oriented design models and formal specifications
Presents an approach to synthesizing functional and robust code from object-oriented design models and Z data and operation specifications. The approach used is based on an integrated notation of the Unified Modeling Language (UML) and a slightly extended Z notation to include object-oriented concepts and structures. Our approach generates fully functional code which can be compiled and executed without modifications. The information from object-oriented analysis and design models along with the formal specifications are combined, analyzed and translated into an intermediate representation from which code can be generated. A research prototype has been developed to demonstrate the feasibility and the effectiveness of our approach.
1493304
On random points in the unit disk
Let n be a positive integer and λ > 0 a real number. Let Vn be a set of n points in the unit disk selected uniformly and independently at random. Define G(λ, n) to be the graph with vertex set Vn, in which two vertices are adjacent if and only if their Euclidean distance is at most λ. We call this graph a unit disk random graph. Let λ = c √ lnn/n and let X be the number of isolated points in G(λ, n). We prove that almost always X ∼ n1−c2 when 0 ≤ c < 1. It is known that if λ = √ (ln n + φ(n))/n where φ(n) → ∞, then G(λ, n) is connected. By extending a method of Penrose, we show that under the same condition on λ, there exists a constant K such that the diameter of G(λ, n) is bounded above by K · 2/λ. Furthermore, with a new geometric construction, we show that when λ = c √ lnn/n and c > 2.26164 · · · , the diameter of G(λ, n) is bounded by (4 + o(1))/λ; and we modify this construction to yield a function c(δ) > 0 such that the diameter is at most 2(1 + δ + o(1))/λ when c > c(δ). ∗This is a preprint of an article accepted for publication in Random Structures and Algorithms c ©2005. †Partially supported by NSF grant DMS-9977354. ‡Partially supported by NSF grant DMS-0245526, DMS-0308827 and a Sloan Fellowship. The author is also affiliated with Dalian University of Technology.
42442258
An approach to animating Z specifications
This paper presents the ZANS approach to animating a large subset of Z specifications. Unlike most other animation approaches that are based on functional or logical programming paradigms, the approach presented transforms the specifications into an imperative intermediate language, which can also serve as the basis of code synthesis from Z specifications. ZANS is showing promise of being an effective tool for requirements validation and assisting students learning Z specification languages.
22388831
PROOF: A Parallel Object-Oriented Functional Computation Model
Abstract Despite the rapid development of parallel computer architectures in recent years, software development technology for parallel processing systems is still largely inadequate. An integrated object-oriented and functional computation model, called PROOF, is developed to facilitate the effective development of software for parallel processing systems. It will fully explore the parallelism in software systems and reduce the development effort by supporting software engineering principles, such as information hiding, modularity, modifiability, and reusability. In PROOF, we achieve the coherent integration of (1) parallelism and inheritance of objects and (2) referential transparency and history sensitivity of functions. The major features and the semantics of PROOF are presented. A parallel programming language and a software development approach based on PROOF are under development. Implementation issues are also discussed.