A distributed real-time database (DRTDB) is a database distributed over a network on several nodes and where the transactions are associated with deadlines. The issues of concern in this kind of database are data consistency and the ability to meet deadlines. In addition, there is the possibility that the nodes, on which the database is distributed, are heterogeneous. This means that the nodes may be built on different platforms and written in different languages. This makes the integration of these nodes difficult, since data types may be represented differently on different nodes. The common object request broker architecture (CORBA), defined by the Object Management Group (OMG), is a distributed object computing (DOC) middleware created to overcome problems with heterogeneous sites. The project described in this paper aims to investigate the suitability of CORBA as a middleware in a DRTDB. Two extensions to CORBA, Fault-Tolerance CORBA (FT-CORBA) and Real-Time CORBA (RT-CORBA) is of particular interest since the combination of these extensions provides the features for object replication and end-to-end predictability, respectively. The project focuses on the ability of RT-CORBA meeting hard deadlines and FT-CORBA maintaining replica consistency by using replication with eventual consistency. The investigation of the combination of RT-CORBA and FT-CORBA results in two proposed architectures that meet real-time requirements and provides replica consistency with CORBA as the middleware in a DRTDB.

<p>Development of distributed real-time applications, in contrast to best effort applications, traditionally have been a slow process due to the lack of available standards, and the fact that no commercial off the shelf (COTS) distributed object computing (DOC) middleware supporting real-time requirements have been available to use, in order to speed up the development process without sacrificing any quality.</p><p>Standards and DOC middlewares are now emerging that are addressing key requirements of real-time systems, predictability and efficiency, and therefore, new possibilities such as component decomposition of real-time systems arises.</p><p>A number of component decomposed architectures of the distributed active real-time database system DeeDS is described and discussed, along with a discussion on the most suitable DOC middleware. DeeDS is suitable for this project since it supports hard real-time requirements and is distributed. The DOC middlewares that are addressed in this project are OMG's Real-Time CORBA, Sun's Enterprise JavaBeans, and Microsoft's COM/DCOM. The discussion to determine the most suitable DOC middleware focuses on real-time requirements, platform support, and whether implementations of these middlewares are available.</p>

<p>A distributed real-time database (DRTDB) is a database distributed over a network on several nodes and where the transactions are associated with deadlines. The issues of concern in this kind of database are data consistency and the ability to meet deadlines. In addition, there is the possibility that the nodes, on which the database is distributed, are heterogeneous. This means that the nodes may be built on different platforms and written in different languages. This makes the integration of these nodes difficult, since data types may be represented differently on different nodes. The common object request broker architecture (CORBA), defined by the Object Management Group (OMG), is a distributed object computing (DOC) middleware created to overcome problems with heterogeneous sites.</p><p>The project described in this paper aims to investigate the suitability of CORBA as a middleware in a DRTDB. Two extensions to CORBA, Fault-Tolerance CORBA (FT-CORBA) and Real-Time CORBA (RT-CORBA) is of particular interest since the combination of these extensions provides the features for object replication and end-to-end predictability, respectively. The project focuses on the ability of RT-CORBA meeting hard deadlines and FT-CORBA maintaining replica consistency by using replication with eventual consistency. The investigation of the combination of RT-CORBA and FT-CORBA results in two proposed architectures that meet real-time requirements and provides replica consistency with CORBA as the middleware in a DRTDB.</p>

Development of distributed real-time applications, in contrast to best effort applications, traditionally have been a slow process due to the lack of available standards, and the fact that no commercial off the shelf (COTS) distributed object computing (DOC) middleware supporting real-time requirements have been available to use, in order to speed up the development process without sacrificing any quality. Standards and DOC middlewares are now emerging that are addressing key requirements of real-time systems, predictability and efficiency, and therefore, new possibilities such as component decomposition of real-time systems arises. A number of component decomposed architectures of the distributed active real-time database system DeeDS is described and discussed, along with a discussion on the most suitable DOC middleware. DeeDS is suitable for this project since it supports hard real-time requirements and is distributed. The DOC middlewares that are addressed in this project are OMG's Real-Time CORBA, Sun's Enterprise JavaBeans, and Microsoft's COM/DCOM. The discussion to determine the most suitable DOC middleware focuses on real-time requirements, platform support, and whether implementations of these middlewares are available.