Henry F. Korth’s research while affiliated with Lehigh University and other places

This paper presents some preliminary results concerning a new user-friendly operating system interface based on the relational data model that is currently under development at the University of Texas at Austin. The premise of our work is that a relational model of the operating system environment wil produce a user and programmer interface to the system: is easier to use, is easier to learn, and allows greater portability as compared with existing operating system interfaces. Our approach is to model elements of the operating system environment as relations and to model operating system commands as statements in a relational language. In adapting the relational model to an operating system environment, we found it necessary to extend the model and improve existing relational languages. The extensions to the relational model are designed to allow a more natural representation of elements of the environment. Our language extensions exploit the universal relation model and utilize the graphical capabilities of modern workstations. The nature of our investigations is ranging from practical implementation issues to the more theoretical questions of modeling and language semanties.

Underlying the structure of a database is the concept of a data model. Modeling is done at three levels of abstraction: physical, logical, and view. The physical level describes how data are stored at a low level and captures implementation details that are not covered in this chapter. The logical level describes the real-world entities to be modeled in the database and the relationships among these entities. The view level describes only a part of the entire database and serves the needs of users who do not require access to the entire database. Typically in a database, the same data model is used at both the logical and the view levels. Data models differ in the primitives available for describing data and in the amount of semantic detail that can be expressed.

A payment system for accessing Internet content is located within an Internet service providers network. The system includes an access controller (106) and a payment authority (108). When an end-user makes a request for a URL, the access controller terminates the request and determines whether the requested URL is one for which a charge for accessing the content referenced by that URL is required. That determination is made by comparing the requested URL with a set of rules that are supplied by all the content providers for which the service provider supports payment. If no match is found, the request is forwarded to the content provider. If a rule is found that matches the requested URL, the end-user is identified and the request is forwarded to the payment authority where a payment policy associated with the matched rule is applied. If the end-user fulfills the requirements of this payment policy, then access to the content is granted. The end-user may fulfill the requirements of the payment policy, for example, through a current subscription to a content provider's site, through an auto-payment agreement in which all charges of less than an agreed upon amount are automatically accepted, or by specifically accepting and agreeing to pay an indicated charge for accessing the requested content. In accepting any such payment arrangement, the end-user's account with the service provider is debited for the appropriate charge and the content provider's account is credited for the end-user's access.

In order for a large dataset of documents to be usable by document analysts, the dataset must be searchable on doc-ument features and on the results of prior analytic work. This paper describes a work-in-progress to develop such a document repository. We describe the types of data we plan to maintain regarding both the documents themselves and analyses performed on those documents. By storing the provenance of all metadata pertaining to documents, the repository will allow researchers to determine dependency relationships among document analyses. Our ultimate goal is to enable geographically separated teams of researchers to collaborate in large document analysis efforts.

A group of database researchers, architects, users, and pundits met in May 2008 at the Claremont Resort in Berkeley, CA, to discuss the state of database research and its effects on practice. This was the seventh meeting of this sort over the past 20 years and was distinguished by a broad consensus that the database community is at a turning point in its history, due toboth an explosion of data and usage scenarios and major shifts in computing hardware and platforms. Here, we explore the conclusions of this self-assessment. It is by definition somewhat inward-focused but may be of interest to the broader computing community as both a window into upcoming directions in database research and

This paper presents an optimistic approach to transaction management for replicated databases. We propose a new transaction management protocol that guarantees global serializability and freedom from distributed deadlocks without relying on any properties of the DBMSs running at the local sites. In comparison to prior protocols, this protocol reduces the communication required to coordinate transactions by a factor of r, where r is the average number of operations per transaction. We also consider implementation issues in reducing message overhead and discuss failure recovery.

At the 2008 Computing Research Association Conference at Snowbird, the authors participated in a panel addressing the issue of paper and proposal reviews. This short paper summarizes the panelists' presentations and audience commentary. It concludes with some observations and suggestions on how we might address this issue in the near-term future.

Multi-core and multithreaded processors present both op- portunities and challenges in the design of database query processing algorithms. Previous work has shown the poten- tial for performance gains, but also that, in adverse circum- stances, multithreading can actually reduce performance. This paper examines the performance of a pipeline of hash- join operations when executing on multithreaded and multi- core processors. We examine the optimal number of threads to execute and the partitioning of the workload across those threads. We then describe a buer-management scheme that minimizes cache conflicts among the threads. Additionally we compare the performance of full materialization of the output at each stage in the pipeline versus passing pointers between stages.

As the performance gap between main memory and modern processors widens, database algorithms must be adapted to be "architecture-aware" for optimal performance. We address this issue using the computation of hash join, one of the most important operations in database query processing, to study the impact of simultaneous multithreading (SMT) and main-memory latency (cache misses) on performance.Prior work [8] has studied cache misses on a simulation based on the Compaq ES40. Our results are obtained by measuring the performance of actual hardware (Intel Pentium and Xeon, and AMD Opteron) first for the single-threaded version of the hash-join algorithm used in the prior work and a new version designed for multiple threads.We found that hardware prefetching from main-memory data into CPU cache as implemented in the architectures we tested significantly reduces the real-world benefit of software prefetching (contrary to prior work on simulated systems). We found that SMT achieved significant speedup for our thread-aware hash join algorithm when compared with a single-threaded execution on the same single processor. Software prefetching also proved beneficial in this environment.