2877433
Mother, May I? OWL-based Policy Management at NASA
Among the challenges of managing NASA’s information systems is the management (that is, creation, coordination, verification, validation, and enforcement) of many different role-based access control policies and mechanisms. This paper describes an actual data federation use case that demonstrates the inefficiencies created by this challenge and presents an approach to reducing these inefficiencies using OWL. The focus is on the representation of XACML policies in DL, but the approach generalizes to other policy languages.
17574900
Opening, Closing Worlds - On Integrity Constraints
In many data-centric applications it is desirable to use OWL as an expressive schema language where one expresses constraints that need to be satisfied by the (instance) data. However, some features of OWL’s semantics, specifically the Open World Assumption (OWL) and not having a Unique Name Assumption (UNA), make it hard to use OWL for this task. What would trigger a constraint violation in a closed world system like a relational database leads to new inferences in OWL. In this paper, we explore how OWL can be extended to accommodate integrity constraints and discuss several alternatives for the syntax and semantics of such an extension. We primarily focus on applications in the Supply Chain Management (SCM) domain but we are also gathering use cases and requirements from many other application areas to assess which of these alternatives provides the best solution.
9634553
Managing Change: An Ontology Version Control System
In this paper we present the basic requirements and initial design of a system which manages and facilitates changes to an OWL ontology in a multi-editor environment. This system uses a centralized client-server architecture in which the server maintains the current state and full history of all managed ontologies. Clients can access the current ontology version, all historical revisions, and differences between arbitrary revisions, as well as metadata associated with revisions. This system will be used by many other ontology based services, such as incremental reasoning, collaborative ontology development, advanced ontology search, and ontology module extraction. Taken holistically, this network of services will provide a rich environment for the development and management of ontology based information systems. 1 Motivation and Requirements We need for a system that manages access to a changing ontology. This requirement is experienced by a variety applications with different stakeholders. An illustrative use case is presented below. A large distributed organization requires integration and alignment of many heterogeneous data sources and information artifacts. They facilitate such integration by employing one or more expressive OWL ontologies that exist in defined relations to data sources, information artifacts, and an enterprise conceptual model. These ontologies, as a critical infrastructure components, have stakeholders throughout the organization and outside its boundaries. Further, they are developed and maintained concurrently by many parties. Individual stakeholders participate in the ontology engineering process in different ways. Some are primarily consumers, but may make detailed edits to areas of the ontologies critical to them. Others are charged with maintaining high-level ontology coherence and use an integrated ontology development environment, such as Protege-OWL, to collaborate with similar editors in realtime, leveraging tools to maintain a dynamic view of the ontology. All stakeholders rely on the ontologies being available and consistent across the organization. This use case illustrates a set of requirements: Client Performance The network is a potential bottleneck of any distributed or client-server system, but the critical work of ontology development is
18665149
Owlgres: A Scalable OWL Reasoner
We present Owlgres, a DL-Lite reasoner implementation written for PostgreSQL, a mature open source database. Owlgres is an OWL reasoner that provides consistency checking and conjunctive query services, supports DL-LiteR as well as the OWL sameAs construct, and is not limited to PostgreSQL. We discuss the implementation with special focus on sameAs and the supported subset of the SPARQL language. Emphasis is given to the implemented optimization techniques which resulted in significant performance improvement. Based on a confidential NASA dataset and part of the DBpedia dataset, we show a typical use case for Owlgres, i.e. given a terminology and a dataset, Owlgres provides querying on a persistent knowledge base with reasoning at query time in the expressivity of DL-LiteR.
38418561
Cryptographic Information Recovery Using Key Recover
A note to readers: the authors consider that all techniques for key recovery may be viewed as having a position on a broad continuum. The only way to avoid misunderstanding is to identify particular techniques by listing their specific characteristics, rather than using multiply-defined terms. Different characteristics have advantages in different environments, so there is no 'best' key recovery technique. The paper notes some typical advantages and disadvantages of several techniques but should not be construed as an endorsement of any particular technique relative to another. Similarly, the authors recognize that terminology may vary from country to country. Cryptographic information recovery techniques provide for the recovery of plaintext from encrypted data. This (exceptional) need arises when the cryptographic keys involved are not available. For example, data files may have been encrypted using a key derived from a now forgotten or misplaced password. Overlapping and confusing terminology has been applied to the techniques of information recovery, including key escrow, key backup, key recovery, and trusted third party (ttp), all of which refer to methods for retrieving, recovering, or re-constructing keys. Even the underlying concept of 'trust' has broad meaning. Instead of attempting to 'define' these terms precisely, a continuum of functionality is defined. Several generic technologies, together with desirable characteristics of cryptographic information/key recovery techniques, are described.
17466351
Aristotle: a system for development of program analysis based tools
Aristotle provides program analysis information, and supports the development of software engineering tools. Aristotle's front end consists of parsers that gather control flow, local dataflow and symbol table information for procedural language programs. We implemented a parser for C by incorporating analysis routines into the GNU C parser; a C++ parser is being implemented using similar techniques. Aristotle tools use the data provided by the parsers to perform a variety of tasks, such as dataflow and control dependence analysis, dataflow testing, graph construction and graph viewing. Most of Aristotle's components function on single procedures and entire programs. Parsers and tools use database handler routines to store information in, and retrieve it from, a central database. A user interface provides interactive menu-driven access to tools, and users can view results textually or graphically. Many tools can also be invoked directly from applications programs, which facilitates the development of new tools. To assist with system development and maintenance, we are also creating support tools for managing bug and test suite databases.
29590207
Combining spatial and scale-space techniques for edge detection to provide a spatially adaptive wavelet-based noise filtering algorithm
New methods for detecting edges in an image using spatial and scale-space domains are proposed. A priori knowledge about geometrical characteristics of edges is used to assign a probability factor to the chance of any pixel being on an edge. An improved double thresholding technique is introduced for spatial domain filtering. Probabilities that pixels belong to a given edge are assigned based on pixel similarity across gradient amplitudes, gradient phases and edge connectivity. The scale-space approach uses dynamic range compression to allow wavelet correlation over a wider range of scales. A probabilistic formulation is used to combine the results obtained from filtering in each domain to provide a final edge probability image which has the advantages of both spatial and scale-space domain methods. Decomposing this edge probability image with the same wavelet as the original image permits the generation of adaptive filters that can recognize the characteristics of the edges in all wavelet detail and approximation images regardless of scale. These matched filters permit significant reduction in image noise without contributing to edge distortion. The spatially adaptive wavelet noise-filtering algorithm is qualitatively and quantitatively compared to a frequency domain and two wavelet based noise suppression algorithms using both natural and computer generated noisy images.
11798209
A Hardware-Assisted Tool for Fast, Full Code Coverage Analysis
Software reliability can be improved by using code coverage analysis to ensure that all statements are executed at least once during the testing process. When full code coverage information is obtained through software code instrumentation, high runtime performance overheads are incurred. Techniques that perform deferred or selective code instrumentation have shown success in reducing run-time overheads; however, the execution profile remains distorted. Techniques have been proposed that use internal processor hardware during the data gathering process, e.g. program counter logging. These approaches have been shown to reduce overheads; but currently trade swift execution for sparse code coverage. By combining the branch-vector hardware designed for debugging modern embedded processors with on-demand code coverage analysis, we have developed a new tool which provides full code coverage, while minimizing performance distortions. Experimental results show a performance impact of only 8 - 12%, while still providing 100% code coverage information.
167449
Rigorous specification and conformance testing techniques for network protocols, as applied to TCP, UDP, and sockets
Network protocols are hard to implement correctly. Despite the existence of RFCs and other standards, implementations often have subtle differences and bugs. One reason for this is that the specifications are typically informal, and hence inevitably contain ambiguities. Conformance testing against such specifications is challenging.In this paper we present a practical technique for rigorous protocol specification that supports specification-based testing. We have applied it to TCP, UDP, and the Sockets API, developing a detailed 'post-hoc' specification that accurately reflects the behaviour of several existing implementations (FreeBSD 4.6, Linux 2.4.20-8, and Windows XP SP1). The development process uncovered a number of differences between and infelicities in these implementations.Our experience shows for the first time that rigorous specification is feasible for protocols as complex as TCP@. We argue that the technique is also applicable 'pre-hoc', in the design phase of new protocols. We discuss how such a design-for-test approach should influence protocol development, leading to protocol specifications that are both unambiguous and clear, and to high-quality implementations that can be tested directly against those specifications.