The technology matrix

intro, components, standards, Java workgroup, corba and hush, summary, Q/A, literature

The component technology field is currently dominated by three players: Microsoft (D)COM, OMG CORBA, and (the youngest player) Sun Microsystems Java. When comparing these technologies with respect to attributes such as distribution, mobility, language and platform independence, and reflective capabilities, we see that there are many differences.

	distribution	mobility	language	platform	reflection
COM	--	--	*	--	+/--
DCOM	+	--	*	+/--	+/--
CORBA	+	--	*	*	+/--
Java/Beans	--	classes	Java	*	+
Java/RMI	+	classes	Java	*	+
Voyager	+	objects	Java	*	+

slide: The technology matrix

First of all, notice that component technology does not automatically mean distribution. For example, JavaBeans and Microsoft COM do not support distribution. Secondly, whereas language independence seemed to be of importance in the pre-Java era, that is for (D)COM and CORBA, it is not so for the Java-based solutions. Finally, platform independence is hard to achieve. But, fortunately, it is on the agenda of all three technologies, including (D)COM.

It is worth mentioning that the three major technologies have a rather different origin. Microsoft (D)COM is primarily a desktop technology, with Office as its killer application, whereas CORBA originated from the need to have an enterprise-wide solution for distributed objects. Java is a special case. It started as a Web-based language, but rapidly took position in the desktop and enterprise world as well.

Java distinguishes itself from the other technologies both with respect to mobility and reflection. As a Web-based language, Java allows for downloading code dynamically, that is class descriptions for instantiating new objects. True mobile objects, that is instantiated objects that migrate themselves, are only possible when using a system such as Voyager, or any of the other Java-based agent ORBs. Java also provides a powerful Reflection API, which allows for various kinds of meta-programming, including the creation of new classes. In comparison, meta-programming facilities of the two other technologies are limited to querying the availability and functionality of interfaces, dynamic method invocation and some dynamic typing.

Trends -- interoperability

It is hard to predict the outcome of the `battle of component technologies'. However, one can observe a convergence of technologies, that is bridges between Java and CORBA, CORBA and (D)COM, and Java and (D)COM/ActiveX. Each of these technologies sets a standard for interoperability. So, eventually some new standard may arise that encompasses them all. In the meantime, we may study the strengths of each of these technologies and establish what major challenges lie ahead. For example, Microsoft COM has demonstrated itself in an unescapable way in Microsoft Office. A related technology, OpenDoc, failed to gain a market position, but is nevertheless taken on by the OMG as document-oriented component technology.

An interesting project in this respect is the K-Office project, which aims at developing an Office Application Suite for the Unix/X11 desktop. It is built upon the KDE GUI environment, and employs a CORBA-based component technology, (nick)named KOM, to interconnect (embed and link) the various document components and their associated tools. See koffice.kde.com .