24298643
Translation of entity-relationship diagrams into relational structures
Abstract An entity-relationship diagram (ERD) is considered to have two conceptual domains: its upper and lower conceptual domains. The semantic properties intrinsic in the upper conceptual domain were studied recently by Lien. In this paper, we discuss the properties inherent in the lower conceptual domain. We show that the latter contains a significant portion of the semantic information of an ERD and helps determine its data representation power. We develop the notions of fundamental functional dependencies (FDs) which can be readily recognized for the lower conceptual domain of an ERD, and regular ERDs which are ERDs such that all the FDs present among their attributes can be derived from their fundamental FDs. Then we give conditions under which a large number of ERDs are equivalent to their underlying relational structures.
17317346
Representative instances and γ-acyclic relational schemes
In this paper, we study under what conditions will a pairwise inconsistent relational database ≪R,r≫ have a universal/representative instance L. If R is γ-acyclic and r satisfies all existence constraints, then it is possible to construct a universal instance L, using unmarked nulls, whose total projections onto R yield exactly the relations in r. We show that L would actually be a representative instance under a set of functional dependencies if R satisfies the additional mild condition: for any functional dependency X → A where A is a single attribute, whenever XA is contained in two relation schemes R and R' of R, it follows that R ∩R' is a relation scheme of R, having X as one of its keys.
13942242
A Scheme of Parallel Processing for MIMD Systems
This paper presents a recognition procedure for parallel tasks in the user program written in a conventional programming language. To establish our program model, it describes the parallelism of the program in tenns of a process flow graph in which the relationships among processes are of predecessors and successors. And finally it presents a parallel processing scheme which realizes automatically the recognition of parallel tasks and schedules these tasks for parallel execution.
45139817
Alternative methods for the reconstruction of trees from their traversals
It is well-known that given the inorder traversal of a binary tree's nodes, along with either one of its preorder or postorder traversals, the original binary tree can be reconstructed using a recursive algorithm. In this short note we provide a short, elegent, iterative solution to this classical problem.
18022126
Construction of Universal Instances for Loop-Free Network Databases Using a Join-Like Operation
In this paper, we give a polynomial-time method to construct effectively the unique universal instance, using as few nulls as possible, from any loop-free network database, via a "minimal information" extension of natural join. Our results can be seen as concretely and quickly implementing the universal relation view for databases which are not pairwise consistent.
120699
Enhancements to the Voting Algorithm
There are several consistency control algorithms for managing replicated files in the face of network partitioning due to site or communication link failures. In this paper, we consider the popular voting scheme along with three enhancements: voting with a primary site, dynamic voting, and dynamic voting with linearly ordered copiee. We develop a stochastic model which compares the file availabilities afforded by each of these schemes. We show that in this model dynamic voting with linearly ordered copies provides the greatest availability.
17662117
Fingerprinting relational databases: schemes and specialties
In this paper, we present a technique for fingerprinting relational data by extending Agrawal et al.'s watermarking scheme. The primary new capability provided by our scheme is that, under reasonable assumptions, it can embed and detect arbitrary bit-string marks in relations. This capability, which is not provided by prior techniques, permits our scheme to be used as a fingerprinting scheme. We then present quantitative models of the robustness properties of our scheme. These models demonstrate that fingerprints embedded by our scheme are detectable and robust against a wide variety of attacks including collusion attacks.
2187643
Enhancing the Controlled Disclosure of Sensitive Information
The so-called “aggregation problem” is addressed, where the issue is how to release only a limited part of an information resource, and foil any attacks by users trying to aggregate information beyond the preset limits. The framework is that of relational databases, where sensitive information can be defined flexibly using view definitions. For each such view, the tuples that have already been disclosed are recorded intensionally rather than extensionally, that is, at each point, sub-view definitions are maintained that describe all the sensitive tuples that have been released to each individual. While our previous work foiled sequences of single-query attacks attempted by individual users, it did not consider multi-query attacks, where a combination of queries is used to invade the sensitive information. In this study we enhance our previous solutions to guard the sensitive information against two kinds of multi-query attacks: join attacks, and complement attacks. We then argue that the enhanced algorithm renders the sensitive information immune to attacks.
286417
Practical broadcast authentication in sensor networks
Broadcast authentication is a critical security service in sensor networks; it allows a sender to broadcast messages to multiple nodes in an authenticated way. /spl mu/TESLA and multi-level /spl mu/TESLA have been proposed to provide such services for sensor networks. However, none of these techniques are scalable in terms of the number of senders. Though multi-level /spl mu/TESLA schemes can scale up to large sensor networks (in terms of receivers), they either use substantial bandwidth and storage at sensor nodes, or require significant resources at senders to deal with DOS attacks. This paper presents efficient techniques to support a potentially large number of broadcast senders using /spl mu/TESLA instances as building blocks. The proposed techniques are immune to the DOS attacks. This paper also provides two approaches, a revocation tree based scheme and a proactive distribution based scheme, to revoke the broadcast authentication capability from compromised senders. The proposed techniques are implemented, and evaluated through simulation on TinyOS. The analysis and experiment show that these techniques are efficient and practical, and can achieve better performance than the previous approaches.
40808730
Dealing with Granularity of Time in Temporal Databases
A question that always arises when dealing with temporal information is the granularity of the values in the domain type. Many different approaches have been proposed; however, the community has not yet come to a basic agreement. Most published temporal representations simplify the issue which leads to difficulties in practical applications. In this paper, we resolve the issue of temporal representation by requiring two domain types (event times and intervals), formalize useful temporal semantics, and extend the relational operations in such a way that temporal extensions fit into a relational representation. Under these considerations, a database system that deals with temporal data can not only present consistent temporal semantics to users but perform consistent computational sequences on temporal data from diverse sources.
16610756
High assurance discretionary access control for object bases
Discretionary access control, based on checking access requests against users' authorizations, does not provide any way of restricting the usage of information once it has been “legally” accessed. This makes discretionary systems vulnerable to Trojan Horses maliciously leaking information. Therefore the need arises for providing additional controls limiting the indiscriminate flow of information in the system. This paper proposes a message filter complementing discretionary authorization control in object-oriented systems to limit the vulnerability of authorization systems to Trojan Horses. The encapsulation property of the object-oriented data model, which requires that access to objects be possible only through defined methods, makes information flow in such systems have a very concrete and natural embodiment in the form of messages and their replies. As a result, information information flow can be controlled by mediating the transmission of messages exchanged between objects. The message filter intercepts every message exchanged between objects to ensure that information is not leaked to objects accessible by users not allowed for it.