The Medium Is the MessageEnterprise messaging offers useful alternatives for integrating enterprise applications
By Greg Barish
The Market and Its PlayersThe market for MOM is made up of a number of vendors, including IBM, Mercator Software Inc., Microsoft, New Era of Networks Inc. (recently acquired by Sybase), Progress Software Corp., Talarian Corp., and Tibco Software Inc. Most analysts agree that IBM is the Goliath of messaging, controlling more than 70 percent of the current market share. The others have their niche, but the IBM MQSeries product family cannot be ignored, and industry players related to the messaging market are nearly always are forced to reckon with it. Still, recent Java technology introduced by Sun Microsystems may shake up the market to some degree, as I describe a bit later. Interestingly, some integration between market players does exist. For example, Tibco offers "adapters" - including ones for the MQSeries - as a means to achieve enterprise integration. Also, IBM works with Mercator to route messages between publishers and subscribers through Mercator software. The Java FactorThe Java Message Service (JMS) API does for messaging vendors what the JDBC API does for database vendors; it provides a standard interface for incorporating messaging into Java applications. As Figure 2 shows, the JMS acts as a wrapper around messaging vendor technology, allowing developers to focus on coding - not the particulars of one vendors' API. In addition to basic messaging functionality, the JMS works with other Java technologies, such as the Java Transactions API, to provide features like distributed transaction support. However, JMS does not provide other features, like load balancing, fault tolerance, security, or quality of service guarantees. JMS supports two general messaging scenarios, point-to-point and publish-and-subscribe. Point-to-point is generally used when messaging occurs between a single producer and a single consumer. Under this scheme, a synchronous form of messaging is actually possible. With publish-and-subscribe, it is possible to have a single producer associated with multiple consumers and to enable a multicast style of communication. Standards like JMS force the industry to ensure that it supports the fundamental features of a messaging service. JMS has been implemented by a number of vendors, including BEA Systems Inc., IBM, Oracle, and Progress. Other companies, including Novell Inc., Tibco, and Sybase, have also endorsed JMS, and some open-source efforts are underway. The emphasis on JMS in this article is not meant to imply that it is the only solution out there. However, it cannot be ignored and, given that many other vendors (including market-leader IBM) are involved in shaping it, this technology is important to underscore. For an example of a typical messaging scenario, see the sidebar A Messaging Solution." And the Message Is ...The intention here is not to say that messaging will solve all enterprise integration issues. It is unquestionably useful and even essential in some contexts. And for many people used to RPC-style distributed system integration, it represents an alternative. Most likely, as enterprise systems continue to integrate, a healthy mix of both synchronous and asynchronous modes of communication will exist. However, as systems become increasingly integrated, at finer and finer levels, the risk of system unavailability looms even greater. For any company, being at the mercy of a downed system you've never heard of is especially alarming. The advantage of asynchronous messaging here is undeniable. What may eventually evolve is a landscape where enterprises rely on messaging as a primary integration technology and only fall back on synchronous-style integration when they really need it. RESOURCESIBM
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