Extensibility and high query performance are important requirements of advanced large scale information systems since complex data analysis often requires the use of application-specific operations that have to be introduced by the user issuing the query. Towards the goal of supporting automatic parallelization of queries containing complex user-defined evaluators in an extensible DBMS, we devised a relevance window model to capture the inherent data lineage characteristics of evaluators on multidimensional data sets. Informally, the relevance window of an evaluator defines the scope of influence input data records have on the value of records in the output data space. An evaluator's relevance window constrains the data partitioning opportunities available for an evaluator.

The ESP2Net project is developing technologies that enable effective collaborative scientific data sharing to support collaboration among scientists, accelerate production of scientific data products, and improve understanding of the science. We have defined a Scientific Experiment Markup Language (SEML) to capture scientific experiments in hypermedia documents as a basic unit of information sharing. A collection of SEML documents can be viewed as an online electronic experiment logbook that captures the entire experiment experience by including the process and interrelationships between experiments to allow an experiment to be re-created. Complementary means of sharing the experiences from scientific experiments (browsing, searching, dissemination, and mining) are provided by integrating OASIS transparent distributed scientific object access, Conquest dynamic distributed query processing services, and active information dissemination services introduced in semantic multicast.

The main concept behind our approach to scientific information sharing is to capture scientific experiments in hypermedia documents as the basic unit of information exchange. We defined SEML (Scientific Experiment Markup Language), based on the XML standard that introduces definitions of tags and links for specific and common information describing scientific experiments. A collection of SEML documents can be viewed as an online electronic experiment logbook that captures the entire experiment. The process and inter-relationships between experiments are modeled to allow an experiment to be re-created, perhaps when input data sets change. We have prototyped ASSISS (Active Semi-Structured Information Sharing System), supporting the browsing, searching and dissemination of XML documents. ASSISS extends scalable active data dissemination technologies developed in the Semantic Multicast Project to provide support for collaborative scientific information dissemination. Within the framework, users' information requests are adaptively clustered. The aggregated information processing and dissemination needs of user groups are then satisfied by a network of dynamic content agents that filters and transforms information in the appropriate manner. SEML is used as the vocabulary against which user profiles are specified, and SEML documents capturing an experiment can be proactively multicasted to groups of users who are interested in some aspect of the activity as the experiments are being conducted.

Massive database sizes and growing demands for decision support and data mining result in long-running queries in extensible object-relational DBMSs, particularly in decision support and data warehousing analysis applications. Parallelization of query evaluation is often required for acceptable performance, yet queries are frequently processed suboptimally due to (1) only coarse or inaccurate estimates of the query characteristics and database statistics being available prior to query evaluation; (2) changes in system configuration and resource availability during query evaluation. In a distributed environment, dynamically reconfiguring query execution plans (QEPs), which adapts QEPs to the environment as well as to the query characteristics, is a promising means to significantly improve query evaluation performance. Based on an operator classification, we propose an algorithm to coordinate the steps in a reconfiguration and introduce alternatives for execution context checkpointing and restoring. A syntactic extension of SQL to expose the relevant characteristics of user-defined functions in support of dynamic reconfiguration is proposed. An example from the experimental system is presented.