We address the problem of providing integrated access to diverse and dynamic information sources. We explain how this problem differs from the traditional database integration problem and we focus on one aspect of the information integration problem, namely information exchange. We define an object-based information exchange model and a corresponding query language that we believe are well suited for integration of diverse information sources. We describe how, the model and language have been used to integrate heterogeneous bibliographic information sources. We also describe two general-purpose libraries we have implemented for object exchange between clients and servers.

The goal of the Tsimmis Project is to develop tools that facilitate the rapid integration of heterogeneous information sources that may include both structured and unstructured data. This paper gives an overview of the project, describing components that extract properties from unstructured objects, that translate information into a common object model, that combine information from several sources, that allow browsing of information, and that manage constraints across heterogeneous sites. Tsimmis is a joint project between Stanford and the IBM Almaden Research Center.

Wrappers provide access to heterogeneous information sources by converting application queries into source specific queries or commands. In this paper we present a wrapper implementation toolkit that facilitates rapid development of wrappers. We focus on the query translation component of the toolkit, called the converter. The converter takes as input a Query Description and Translation Language (QDTL) description of the queries that can be processed by the underlying source. Based on this description the converter decides if an application query is (a) directly supported, i.e., it can be translated to a query of the underlying system following instructions in the QDTL description; (b) logically supported, i.e., logically equivalent to a directly supported query; (c) indirectly supported, i.e., it can be computed by applying a filter, automatically generated by the converter, to the result of a directly supported query. 1 Introduction A wrapper or translator [C + 94, PGMW95] is a s...

Mediators are used for integration of heterogeneous information sources. We present a system for declaratively specifying mediators. It is targeted for integration of sources with unstructured or semi-structured data and/or sources with changing schemas. We illustrate the main features of the Mediator Specification Language (MSL), show how they facilitate integration, and describe the implementation of the system that interprets the MSL specifications.

The goal of the Tsimmis Project is to develop tools that facilitate the rapid integration of heterogeneous information sources that may include both structured and unstructured data. This paper gives an overview of the project, describing components that extract properties from unstructured objects, that translate information into a common object model, that combine information from several sources, and that allow browsing of information.

. This paper presents a framework for data integration that is based on using "Squirrel integration mediators" that use materialization to support integrated views over multiple databases. These mediators generalize techniques from active databases to provide incremental propagation of updates to the materialized views. A framework based on "View Decomposition Plans" for optimizing the support of materialized integrated views is introduced. The paper describes the Squirrel mediator generator currently under development, which can generate the mediators based on high-level specifications. The integration of information by Squirrel mediators is expressed primarily through an extended version of a standard query language, that can refer to data from multiple information sources. In addition to materializing an integrated view of data, these mediators can monitor conditions that span multiple sources. The Squirrel framework also provides efficient support for the problem of "object matchin...

s Service (CAS) registry number (7439-97-6), "raw" CAS number (dashes removed---7439976), and common name ("quicksilver "). Within an ontology, each class has one or more slots, where each slot has a conceptual domain name with a canonical value domain over which all agents communicate when referring to that slot. This mapping problem has several manifestations, which we relate roughly in the order they have been addressed in the literature (insofar as they are addressed at all): ffl Traditional: Mapping between schemas can take place by imposing a view on that information and/or defining functions to translate the data from one value domain to another, as is currently done in relational databases, e.g., [9]. This type of mapping provides little support for semantics, but rather relies on the structure of the data. ffl Ontology-based: A common ontology is defined with well-specified semantics for the concepts it describes. Mapping between a schema and an ontology is done on a semantic...

An increasing number of business users and software applications need to process information that is accessible via multiple diverse information systems, such as database systems, file systems, legacy applications or web services. We describe the Enosys XML Integration Platform (EXIP), a commercial XQuery-based data integration software platform that provides a queryable integrated view of such information. We describe the platform architecture and describe what the main principles and challenges are for the query engine. In particular, we discuss the query engine architecture and the underlying semistructured algebra, which is tuned for enabling query plan optimizations. 1

Access control is a fundamental concern in any system that manages resources, e.g., operating systems, file systems, databases and communications systems. The problem we address is how to specify, enforce, and implement access control in distributed environments. This problem occurs in many applications such as management of distributed project resources, e-newspaper and payTV subscription services.

During the last years our research efforts were inspired by two different needs. On one side the number of non-expert users accessing databases is largely growing. On the other side, information systems will be no longer composed by a single centralised architecture, but rather by several heterogeneous component systems. In order to address such needs we have designed a new query system, having both user-oriented and multidatabase features. The system main components are an adaptive visual interface, providing the user with different and interchangeable interaction modalities, and a "translation layer", which creates and offers to the user the illusion of a single homogeneous schema out of several heterogeneous components. Both components are founded on a common ground, i.e. a formally defined and semantically rich data model, the Graph Model, and a minimal set of Graphical Primitives, in terms of which general query operations may be visually expressed. The Graph Model has...