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.
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.
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.
10245361
Information systems research at George Mason University
George Mason University began as an independent state university in 1972. Its development has been marked by rapid growth and innovative planning, resulting in an enrollment of more than 24,000 students in 1997. It is located in Fairfax, Virginia—about fifteen miles southwest of Washington, DC—near many governmental agencies and industrial firms specializing in information-intensive products and services.
Information and Software Systems Engineering (ISSE) is one of six departments in GMU's School of Information Technology and Engineering (SITE). Established in 1985, SITE has approximately 90 faculty and ISSE has 13 full time faculty. ISSE is a rapidly growing department with wide-ranging teaching and research interests. The department offers no undergraduate degree programs and Master of Science degrees in Information Systems (MSIS) and Software Engineering (SWSE). MSIS has about 800 students and the SWSE has approximately 400 students enrolled. The MSIS program graduates about 120 students and the SWSE program awards 40 degrees per year. ISSE faculty participate in the SITE doctoral program in Information Technology. ISSE Faculty chair the committees of more than one third of the doctoral students in the SITE program, which currently graduates about 30 PhDs per year.
Two research centers are associated with the department: The Center for Secure Information Systems (Sushil Jajodia, Director) and the Center for Information Systems Integration and Evolution (Larry Kerschberg, Director).
Departmental research in information systems is supported by grants and contracts from several sources. The following awards have been received so far for the academic year 1997-1998 and beyond: Knowledge Rovers: A Family of Intelligent Software Agents for Logistics for the Warrior. Defense Advanced Research Projects Agency (co-PIs: Kerschberg, Gomaa, Jajodia, Motro)
Electronic Commerce for Logistics, Teaming Agreement with American Management Systems for DARPA BAA 95-25 Logistics Research and Development (co-PIs: Kerschberg, Gomaa, Jajodia, Motro)
Linear Constraint Databases, NSF Research Initiation Award (PI: Brodsky)
Linear Constraint Programming, ONR (co-PI: Brodsky with late Kannelakis (PI), Van Hentenryck, and Lassez)
Towards Expressive and Efficient Queries on Sequenced Data, NSF Research Initiation Award (PI: Wang)
Supporting Multiple time granularities in Query Evaluation and Data Mining, NSF (co-PIs: Jajodia, Wang)
Fine Granularity Access Controls in World Wide Web, NSA (PI: Jajodia)
Information Flow Control in Object-Oriented Systems NSA (PI: Jajodia)
Exploring Steganography: Seeing the Unseen, NSA (PI: Jajodia)
Trusted Recovery from Information Attacks, Rome Laboratory (co-PIs: Jajodia, Ammann)
A Unified Framework for Supporting Multiple Access Control Policies, DARPA (PI: Jajodia)

The remainder of this article provides a brief overview of our research followed by a selected list of publications. More detailed information is available at www.isse.gmu.edu.
7081422
Testing complex temporal relationships involving multiple granularities and its application to data mining (extended abstract)
A vacuum cleaner structure wherein a nozzle is mounted on a wheeled carriage, the front portion of the carriage being vertically adjustably positioned relative to the subjacent surface on which the wheels are disposed. Thus, the vacuum cleaner structure is adjustable for use with different height pile carpeting, i.e., from relatively low pile carpeting to deep shag carpeting. The wheel adjusting means includes a control member adjustably carried on the nozzle and means for adjusting the relationship of the front wheels of the carriage to the carriage as a function of adjustment of the control member. The adjustment control may include means for locking the control in different preselected positions of adjustment.
17883462
Redirection policies for mission-based information sharing
When an access decision function denies a data access request by a mission participant in a mission-critical situation, the mission often suffers. In this paper, we propose a sharing control mechanism that computes and executes requests that are mission-related to denied requests. We extend the Flexible Authorization Framework (FAF)with predicates and hierarchies that permit us to specify authorization rules over denied requests and mission-specific relationships. We illustrate our techniques using a prototypical information sharing scenario, namely an emergency first-responder scenario.
32784248
Measuring the effect of commutative transactions on distributed database performance
Abstract In this paper, we consider algorithms that permit every site in a partitioned system to perform new updates. Because this may result in independent updates to items in different partitions, conflicts among transactions are bound to occur. Commutative transactions can be used to reduce the number of these conflicts. We develop a probabilistic model to estimate the possible reduction in conflicts if we incorporate this notion of commutativity. Our results show that the additional efforts to recognize this commutativity are not beneficial unless the number of transactions that commute with each other is significantly large.