Model-based user interface development environments show promise for improving the productivity of user interface developers, and possibly for improving the quality of developed interfaces. While model-based techniques have previously been applied to the area of database interfaces, they have not been speci®cally targeted at the important area of object database applications. Such applications make use of models that are semantically richer than their relational counterparts in terms of both data structures and application functionality. In general, model-based techniques have not addressed how the information referenced in such applications is manifested within the described models, and is utilised within the generated interface itself. This lack of experience with such systems has led to many model-based projects providing minimal support for certain features that are essential to such data intensive applications, and has prevented object database interface developers in particular from bene®ting from model-based techniques. This paper presents the Teallach model-based user interface development environment for object databases, describing the models it supports, the relationships between these models, the tool used to construct interfaces using the models and the generation of Java programs from the declarative models. Distinctive features of Teallach include comprehensive facilities for linking models, a¯exible development method, an open architecture, and the generation of running applications based on the models constructed by designers.
A Federated Information System requires that multiple (often heterogenous) information systems are integrated to an extent that they can share data. This shared data often takes the form of a federated schema, which is a global view of data taken from distributed sources. One of the issues faced in the engineering of a federated schema is the continuous need to extract metadata from cooperating systems. Where cooperating systems employ an object-oriented common model to interact with each other, this requirement can become a problem due to the type and complexity of metadata queries. In this research, we specified and implemented a metadata software layer in the form of a high-level query interface for the ODMG schema repository, in order to simplify the task of integration system engineers. Two clears benefits have emerged: the reduced complexity of metadata queries during system integration (and federated schema construction) and a reduced learning curve for programmers who need to use the ODMG schema repository.
View mechanisms play an important role in restructuring data for users, while maintaining the integrity and autonomy for the underlying database schema. Although far more complex than their relational counterparts, numerous object-oriented view mechanisms have been specified and implemented over the last decade. These view mechanisms have served different functions: view schemata for object-oriented databases; object views of relational (and other) database systems, and the formation of federated schemata for distributed information systems. In the latter category there is still a significant amount of research required to construct a view language powerful enough to support federated views. Such a language (or set of languages) should support not only object views, but also a wrapper specification language for external information sources, and a set of restructuring and integration operators. Furthermore, with the advent of standard models and technologies such as CORBA for distribution, ODMG for storage, and XML for web publishing, these languages should be based upon, or cooperate with, these standards. In this research, we present a view mechanism which retains the semantic information incorporated in ODMG schemata, provide a set of operators which facilitate the restructuring and integration necessary to merge schemata, and provide wrappers to heterogenous systems such as legacy systems, ODBC databases, and XML data sources.
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