We present a general model for classification structures that supports object role modelling. Objects can be associated with many roles simultaneously in a way that provides multiple classification views over objects. Further, objects can change their roles through migration within a classification graph. Object migration is controlled through the structure of the classification graph and the types of the nodes, thereby restricting possible evolution paths. We show how the model can be generalised to classification structures over relationships. In addition, we consider approaches to constraint maintenance in the case of object and relationship evolution. 1 Introduction Entities of application domains change their roles during the course of their lifetime. To reflect these role changes in the corresponding database application system, the system must have mechanisms to support and control the evolution of the objects which represent those entities. Support for object evolution requires...

We present the object-oriented multi-tier application framework OMS Java which is independent of the underlying database management system (DBMS). We detail the storage management component and sketch which part of the framework has to be extended when introducing a new DBMS. We compare versions of OMS Java using the persistent storage engine ObjectStore PSE Pro for Java, the object-oriented DBMS Objectivity/DB, the objectrelational DBMS Oracle and the proprietary DBMS Berkley DB. 1 Introduction Most applications create data that extends the life of an application process making it necessary that application objects can be stored in and retrieved from non-volatile storage. Furthermore, looking at pure object-oriented applications, i.e. applications developed entirely using an objectoriented language environment such as Java [KA96], application objects typically refer to many other application objects resulting in complex object hierarchies. It is therefore crucial to find mechan...

. We showhow model extensibility of object-oriented data management systems can be achieved through the combination of a highlevel core object data model and an architecture designed with model extensibility in mind. The resulting system, OMS#Java, is both a general data management system and a framework for the developmentof advanced database application systems. All aspects of the core model # constructs, query language and constraints # can easily be generalised to support, for example, the management of temporal, spatial and versioned data. Speci#cally,we showhow the framework was used to extend the core system to a temporal object-oriented database management system. 1 Introduction Extensibility has often been considered a purely architectural issue in database management systems #DBMS#. In the 1980s, there was an increase in the various forms of DBMS that appeared --- many of whichwere tailored to speci#c application domains such as Geographical Information Systems or ...

We present an overview of the generic object-oriented data model OM together with a methodology for developing database application systems based on the OM model and its associated system OMS. Fundamental to our approach is a refinement process which retains the same structural model from the conceptual modelling phase through to implementation on one of a variety of implementation platforms. 1 Introduction Ideally, both the development and use of a database application system should be based on a single abstract model of the application domain. This means that the same basic structural model should support all of the development stages from conceptual modelling through to implementation. It follows that the underlying data model should be: ffl semantically expressive for conceptual modelling, ffl independent of the implementation platform, since this is often determined after the initial design phase, ffl supported on a number of implementation platforms including at least one for ...

Operational transformation has been identified as an appropriate approach for consistency maintenance in realtime collaborative editing systems. Various operational transformation algorithms [2,10,16,15,12,19] can be applied only for applications that use a linear representation of the document. We propose a new algorithm called treeOPT (tree OPerational Transformation) that relies on a tree representation of the document. Applications using this algorithm achieve better efficiency, the possibility of working at different granularity levels and improvements in the semantic consistency. Our algorithm applies the same basic mechanisms as the existing operational transformation algorithms recursively over the different document levels.

We present various client-server database architectures in which components of a database system execute on the Web client. The Web components described include a general object browser, cooperative client-server caches, a personal Web assistant and developer tools for database design and prototyping. All of these have been implemented as part of the OMS database development suite. Additionally, we describe a multi-tier architecture in which an entire metadatabase component implemented in OMS Java executes on the Web client in support of intelligent data collection and querying in scientific information systems. 1.

We present an object-oriented data model and system that supports the development of database application systems through a combination of rapid prototyping and refinement. Prototyping is performed on an abstract application model and is independent of any implementation platform -- supporting not only the design stage, but also analysis and requirements modelling. The underlying model, OM, has a two-level structure which reflects the two aspects of object-oriented database application systems -- data modelling and programming. We are therefore able to cleanly integrate ideas from both the database and software engineering communities and achieve compatibility with object models used in both. Keywords: Object-oriented database systems, rapid prototyping, database design. 1 Introduction The design and implementation of object-oriented database application systems presents a software engineering challenge in that it encompasses both application program development and database design. ...

In this paper, we describe an integrated document management system based on the objectoriented database system OMS. The underlying idea is to replace the current vision of a file system with that of a document database system, thereby offering higher-level user support for the management of all forms of computer-stored information and work activities. The objectoriented database system provides access to existing tools such as editors and compilers through object methods, while providing standard database features for managing dependencies between documents, queries and controlled information sharing. In particular, the OMS system supports powerful methods for document classification independent of the type of the documents. This extended database view of a file system allows the users to handle documents at a logical level of abstraction independent of the physical file system. 1 Introduction In most implementations of file systems in modern operating systems, the level of abstracti...

We describe an approach to the coordination of application systems based on the modelling and maintenance of inter-system dependencies expressed as data constraints together with update propagation rules. These dependencies are specified by a Coordination Model which comprises a Coordination Interface for each application system together with a global Coordination View. A Coordination Interface describes local object types relevant for systemwide coordination. The Coordination View describes the subsystems, their globally important object types and the relationships between those object types. Additionally, the Coordination View specifies actions to restore global consistency in the event of constraint violations, thereby providing system coordination. Specifically, we describe how this approach has been adopted in a prototype Computer Integrated Manufacturing (CIM) system based on the coordination of CIM subsystems. In this CIM system, the Coordination Model is specified using the NIA...

We address the issue of how to provide effective access to database systems and their application services on the Internet. To avoid typical Internet delays in downloading data, users may register with a database service to obtain an improved service which ensures that required data is prefetched into their local cache. This service is provided by cooperating server and client agents which use a combination of application and user profiles to determine which information should be prefetched and when. Using this approach, we are developing information services based on the ETH developed object-oriented database system, OMS. As part of this project, we have developed a World-Wide Web Interface to OMS which mimics the standard style of an object-oriented database graphical browser. In particular, we describe how the approach has been used in constructing an integrated information service for snow and avalanche data for Switzerland. 1 Introduction More and more sites are providing Interne...