Data CORBA

The call back queries used in these steps are not purely queries to source databases. For example, the needed simulation results of the reactor are results of an aggregation function. In this sense the results are the results of a (highly complex) query on the data warehouse store. As simulating is a time consuming and expensive task we also store the results in the data warehouse for reuse. To gain access to the units the DB trader contains meta information about the CAPE-OPEN components. As a result of the usage of the CAPE-OPEN compliant units we do not need to handle very different simulators such as Aspen Plus, Pro/II or gPROMS, but only have to create the CAPE-OPEN objects used by the units. This especially concerns the material object for each substance contained in the input ports of the unit. The process data warehouse produces these CORBA objects and is then able to start the simulation of the unit. 

The data transfer in CORBA is realized by the ORB which transmits requests... 

As all communication was envisaged to be based on CORBA, the first step was an investigation of data transfer methods provided by CORBA, to find out if the communication mechanisms are suitable for the application domain. 

The CORBA implementation Orbix from IONA Technologies [750] was used in the project. Yet, before implementing all project software on top of Orbix, it was examined with regard to performance in data transmission [447]. Orbix is a fairly efficient implementation. It implements large parts of the CORBA specifications, and has a very broad installation base in companies. Another important criterion was Orbix provision of extended features that support object and communication management. Although it had a number of deficiencies at the time of decision making, it was clear that it was rapidly developed further [421]. 

Studies on Orbix (version 2.3 later a transition to a newer version was made) consisted of the analysis of the influence of different hardware architectures on communication in CORBA, the overhead produced by communication operations, a comparison between different modes of data transfer, the applicability of updating methods, and the realization of multicast communication. Synchronous, oneway, deferred synchronous, and the use of the CORBA Event Service for asynchronous communication were investigated. The data transferred in each experiment were strings, due to the lack of container objects in CORBA. 

Relatively low data transfer rates of some Kbyte/s reduce the usefulness of CORBA. Even if concrete values depend on server and network infrastructure, the general conclusion is that CORBA should not be used for transmission of continuous data streams like e.g. video or audio. 

These results had shown that it is not recommended to do all data transfer via CORBA. For certain data types, e.g. video and audio data, other transfer mechanisms had to be integrated. Nevertheless, for small amounts of data, especially control information and for monitoring purposes, it was decided to use CORBA because of its ability to handle heterogeneity. 

Thifien, D., Linnhoff-Popien, C., Lipperts, S. Can CORBA fulfill data transfer requirements of industrial enterprises In Proceedings of the U International Enterprise Distributed Object Computing Workshop, Gold Coast, Australia, pp. 129-137. IEEE Computer Society Press, Los Alamitos (1997)... 

This provides much more flexibility, as the data objects returned by the object loader can be passed to other programs, such as those written in C, C++, Java Perl or Python, passed over the Internet via a CORBA server or used to create more interesting views, such as a view including an image made from data in the object (an example of this can be seen in Figure 1.11 further in this Chapter). 

Because there are different aspects to interoperability standards and because there has been standardization interest in this area for over a decade, the result is a plethora of APIs, data formats, and standards bodies targeted at a number of technologies, including C, Java, CORBA, XML, and SOAP. The more recent interest in modeling and standardizing business-to-business processes has made the situation even more confusing, with considerable debate around the overlap between workflow and business processes and whether the pre-existing workflow standards are even appropriate for peer-to-peer business processes [WS6]. 

Needless to say, there are other ways to exchange data like the Common Object Request Broker Architecture (CORBA) (15). This standard provides an intermediary object-oriented layer that handles access to the data between server and client. Another recently emerging way to exchange data is web services (16), which will be described later. 

Mailing J, Figusch V, Corba J, Hanic F (1974) Crystal data on calcium borate chloride, CajBOaCl. 7 402... 

Figure 5.1. Main data mining approaches and supporting technologies (abbreviations ILP — inductive logic programming, MLPs — multilayer perceptrons, RBF — radial basis functions networks, ARTMAP — adaptive resonance theory mapping networks, DOOT — distributed object-oriented technologies, CORBA — common object request broker, RMI — remote method invocation).

Trends in open-source middleware suggest the Distribution Data Service (DDS) [33] is the natural successor of CORBA for the domains where CORBA is applied. It is also from OMG (2003) and although it is more than 10 years old, changes in these markets are not introduced at the same speed as other sectors (e.g. Internet technologies) and DDS is only now being introduced in some of them. 

DDS shares much of the philosophy of CORBA but is centered on data. In fact, it resembles the real-time event service of TAO [34]. DDS is designed to support heterogeneity, dynamism, different systems Systems-of-Systems programming. 

CORBA data objects are managed in a very flexible fashion. At the most basic level, CORBA is a standard for distributed objects. CORBA allows an application to request an operation to be performed by a distributed object and arranges for the results of the operation to be returned back to the application... 

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