Protocols for Integrity Constraint Checking in Federated Databases

A federated database is comprised of multiple interconnected database systems that primarily operate independently but cooperate to a certain extent. Global integrity constraints can be very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. This paper presents a threefold contribution to integrity constraint checking in federated databases: (1) The problem of constraint checking in a federated database environment is clearly formulated. (2) A family of protocols for constraint checking is presented. (3) The differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed by the protocols, and processing and communication costs. Thus, our work yields a suite of options from which a protocol can be chosen to suit the system capabilities and integrity requirements of a particular federated database environment

Integrity Constraint Checking in Federated Databases

A federated database is comprised of multiple interconnected databases that cooperate in an autonomous fashion. Global integrity constraints are very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. The paper presents a threefold contribution to integrity constraint checking in federated databases: (1) the problem of constraint checking in a federated database environment is clearly formulated; (2) a family of cooperative protocols for constraint checking is presented; (3) the differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed, and costs involved. Thus, we provide a suite of options with protocols for various environments with specific system capabilities and integrity requirement

Validating constraints with partial information: research overview

We are interested in the problem of validating the consistency of integrity constraints when data is modified. In particular, we consider how constraints can be checked with only "partial information". Partial information may include: (1) the constraint specifications only, (2) the constraint specifications and the modified data, or (3) the constraint specifications, the modified data, and portions ofthe existing data. Methods for constraint checking with partía! ínformation can be much more efficient than traditional constraint checking methods ( e.g. because work is done at compile time, or because less data is accessed). Partial information methods also enable constraint checking in scenarios where tradítíonal constraint checking methods fail (e.g. in distributed environments where not all data is accessible). We explain how existing methods and results for query containment and for independeñce can be applied to problems (1) and (2) above, and we give an overview of our research into problem (3)

Adaptive Filters for Continuous Queries over Distributed Data Stream

We consider an environment where distributed data sources continuously stream updates to a centralized processor that monitors continuous queries over the distributed data. Significant communication overhead is incurred in the presence of rapid update streams, and we propose a new technique for reducing the overhead. Users register continuous queries with precision requirements at the central stream processor, which installs filters at remote data sources. The filters adapt to changing conditions to minimize stream rates while guaranteeing that all continuous queries still receive the updates necessary to provide answers of adequate precision at all times. Our approach enables applications to trade precision for communication overhead at a fine granularity by individually adjusting the precision constraints of continuous queries over streams in a multi-query workload

Implementing Parameterized Range Types in an Extensible DBMS *

Abstract A parameterized type defines a family of related types. For example, a single parameterized type ARRAY provides a common definition for array of INTEGER, array of FLOAT, and array of rows of a certain row type. SQL3 proposes support for user-defined parameterized types (or UDPTs for short), but we have yet to see any full implementation in a commercial DBMS. In this paper, we show how we implemented UDPTs Range and RangeSet using the DataBlade and Fastpath extensibility features of Informix. We also describe the application of these UDPTs in building a temporal database with TSQL2-like features. We found that implementing temporal database primitives using UDPTs required much less development effort and is more flexible than our earlier approach that used regular, non-parameterized user-defined types. We report some lessons learned in the implementation process, and propose a "wish list" of DBMS extensibility features required for full support of UDPTs. Although our implementation is based on Informix, we expect our experience and findings to be relevant to anyone implementing UDPTs in an extensible DBMS