yosikawaQkyoto-su.ac.jp Abstract: This paper introduces ILOG ( a declarative language in the style of (stratified) datalog ( which can be used for querying, schema translation, and schema augmentation in the context of object-based data models. The semantics of ILOG is based on the use of Skolem functors, and is closely related to semantics for object-based data manipulation languages which provide mechanisms for explicit creation of object identifiers (OIDs). A normal form is presented for ILOG ’ programs not involving recursion through OID creation, which identifies a precise correspondence between OIDs created in the target, and values and OIDs in the source. The expressive power of various sublanguages of ILOG ’ is shown to range from a natural generalization of the conjunctive queries to the object-based context, to a language which can specify all computable database translat.ions (up to duplicate copies). The issue of testing vuliilityof ILOG programs translat.ing one semantic schema to another is studied: cases are presented for which several-validity issues (e.g., functional and/or subset relationships in the

this report, we examine the technical challenges to integration, critique the available tools and resources, and compare the cost and advantages of various methodologies. We begin by analyzing the basic steps in strict and complete integration: 1) transformation of the various schemas to a common data model; 2) matching of semantically related schema objects; 3) schema integration; 4) transformation of data to the federated database on demand; and 5) matching of semantically equivalent data. Some progress has been made on generic problems such as (1) and (3) within the wider database community, but issues of semantics (steps (2) and (5)) have only been dealt with any degree of success by domain experts within the biological community. We then look at the solution space of integration strategies as defined by two axes, the "tightness" of federation and the "degree" of instantiation, discuss where various solutions fall on this plane, and examine their cost and advantages/disadvantages. Finally, we examine technical challenges that are not -3- July 12, 1995

msiegelQsloan.mit.edu In this paper we describe a rule-based ap-proach to semantic specification that can be used to establish semantic agreement be-tween a source and receiver. Query process-ing techniques use these specifications along with conversion routines and query modifi-cation to guarantee correct data semantics. This work also examines the effect of chang-ing data semantics. These changes may oc-cur at the source of the data or they may be changes in the specifications of the dat,a semantics for the application, Methods are described for detecting these changes and for determining if the database can continue to supply meaningful data to the application. These methods for semanlic reconcilia2ion are necessary for determining logical connec-tivity between a data source (database) and a data receiver (application). Though de-scribed in terms of the source-receiver model, these techniques can also be used for seman-tic reconciliation and schema integration for multidatabase systems. Keywords[data dictionaries, heterogeneous databases, metadata, query modification, schema integration, seman-tic conflicts] 1

Service order provisioning is an important telecommunication application that automates the process of providing telephone services in response to the customer requests. It is an example of a multi-system application that requires access to multiple, independently developed application systems and their databases. In this paper, we describe the design and implementation of a prototype system 1 that supports the execution of the Flexible Transactions and its use to develop the service order provisioning application. We argue that such approach may be used to support the development of multi-system, flow-through processing applications in a systematic and organized manner. Its advantages include fast and easy specification of new services, support for testing of the declaratively specified work-flows, and the specification of potential concurrency among the tasks constituting an application.

This paper studies heterogeneous database systems from the multiple (poly) source @rrt) perspective. It aims at addressing issues such as “where is the data from ” and “which intermediate data sources were used to arrive at that data ”- issues which are critical to many users in utilizing information composed from multiple sources. Specifically, it presents a polygen model for resolving the Data Source Tagging and Intermediate Source Tagging problems. Secondly, it presents a data-driven query translation mechanism for mapping a polygen query into a set of local queries dynamically. A concrete example is also provided to exemplify polygen query processing. The significance of this paper lies not only in a precise characterization of a practical problem and a solution per se, but also in the establishment of a foundation for resolving many other critical research issues such as domain mismatch, semantic reconciliation, and data conflict amongst data retrieved from different sources. In a federated database environment with hundreds of databases, all of these issues are critical to their effective USt!. I.

The end of the tunnel is actually here! Now is the time to start the next stage, and I would like to do so by first recognizing the people that made the difference throughout my Ph.D. study years. First and foremost I must thank Nauro, my better half, for always being there, making it all possible and worthwhile. This whole process has brought us even closer. Both of our families deserve recognition for caring, cheering, and trying to understand the various stages involved. Barry Boehm, my advisor, has been a very special person to me. Not only has he supported me throughout the years, mentoring me when I needed, but he has also been a good friend. I deeply appreciate that. My committee members Dave Wile and Eb Rechtin must also be acknowledged. I must thank Dave for his deep involvement, actually bringing up new ideas and helping me evolve them, as well as for the occasional pub stops during various workshops. Dr. Rechtin was probably the most involved and knowledgeable outside committee member in history. He not only devoted his time to reading the material I gave him, but always

Today's networked software engineering environment is characterized by a multitude of autonomous, heterogeneous information repositories, a variety of incompatible user interfaces, diverse, unconventional data types, including text, graphics, and possibly video and sound, rapid change, both in structure and content, and multiple ways of viewing relationships among the same information items. Existing information storage mechanisms fail to combine diverse data types/models, complex objects and storage structures, personal views and organizations of shared objects, access to distributed, heterogeneous repositories, and ease of evolution. This paper examines these issues and describes a Distributed Hypertext architecture that provides transparent access to autonomous, heterogeneous software object repositories, resulting in both a powerful organizational tool and a simple yet effective integration mechanism. Keywords: Hypertext, Distributed Systems, Heterogeneous Distributed Object Manage...

Abstract. Most virtual database systems are suitable for environments in which the set of member information sources is small and stable. Consequently, present virtual database systems do not scale up very well. The main reason is the complexity and cost of incorporating new information sources into the virtual database. In this paper we describe a system, called Autoplex, which usesmachine learning techniques for automating the discovery of new content for virtual database systems. Autoplex assumes that several information sources have already been incorporated (\mapped") into the virtual database system by human experts (as done in standard virtual database systems). Autoplex learns the features of these examples. It then applies this knowledge to new candidate sources, trying to infer views that \resemble " the examples. In this paper we report initial results from the Autoplex project. 1

A method for integrated concurrency control and recovery, applicable to heterogeneous multidatabase systems is proposed 1 . The role of the participant in the two-phase commit protocol is laid on an entity called 2PC Agent associated with the local database system. The main importance of the method is in preserving global serializability in the presence of unilateral aborts and site failures. The method requires the participating database systems to use the strict two-phase locking or a comparable rigorous concurrency control policy. Introduction There has recently been much interest in integrating pre-existing databases managed by heterogeneous database management systems (DBMS). This is understood to be caused by the need to eliminate "islands of information" [11] and, generally, the necessity to improve the interoperability of database systems [23]. There are various architectures supporting these objectives. The multidatabase architecture [25] is characterized by preserving vari...

The integration of information from multiple databases has been an enduring subject of research for almost 20 years, and many di erent solutions have been attempted or proposed. Missing from this research has been a uniform framework. Usually, each solution develops its own ad-hoc framework, designed to address the particular aspects of the problem that are being attacked and the particular methodology that is being used. To address this situation, in this paper we de ne a formal model for multidatabases, which we call Multiplex. Multiplex is a simple extension of the relational model, which may serve as a uniform abstraction for many previous ad-hoc solutions. Multiplex is based on formal assumptions of integrability, which distinguish between scheme and instance reconcilability among independent databases. Multiplex supports database heterogeneity, and it provides several degrees of freedom that allow it to model actual situations encountered in multidatabase applications. In addition, in situations in which a single answer is not obtainable (either because the global query is not answerable, or there are multiple candidate answers), Multiplex de nes approximative answers. Finally, Multiplex provides a practical platform for implementation. A prototype of such an implementation is described brie y.