Interoperability: You can count on MOM for message delivery

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When companies want reliable message delivery among applications, they turn to MOM - message-oriented middleware.

Message-oriented middleware (MOM) is a type of connectivity software that helps integrate applications by passing messages among them.

MOM is critical for large, distributed companies that need to link multiple internal applications, or in any company that's trying to communicate with suppliers and customers and needs to hook up with their systems. MOM is an important infrastructure in the world of B2B commerce. And most of the application integration players incorporate MOM into their server platforms.

Sally Hudson, an analyst who covers middleware and other types of integration technologies for consulting firm IDC in Framingham, Mass., explains more about MOM.

Q: What's your definition of MOM?

A: It's a way of communicating among applications - a request for information, a request for action. Applications make requests by passing messages directly to the middleware. MOM inherently supports an event-driven mode of processing, and communication may be synchronous or asynchronous. Event-driven is another term for action item or function call. Let's say you work in a bank, and you put in a request for a loan approval. Events will take messages to several places: They send off a request for the person's credit history, which in turn generates an event and kicks off credit check. Another request might look for the person's current accounts at the bank or check on the applicant's current employment. Another example is that you can say that every time the Dow goes up to a certain level, get me the top 10 companies in terms of volume. MOM can also do publish-and-subscribe: I want to be notified every time a certain vendor has a sale on red swimsuits. The event becomes the red swimsuit sale, which in turn triggers the message.

Q: What are the general advantages and disadvantages to the technology?

A: MOM is an older technology, so there aren't a lot of bugs to be worked out. There's nothing sexy about MOM. It's plumbing - but you can't live in a house without plumbing. Usually customers are looking to augment MOM with other types of application integration activities. The fundamental beauty of MOM is reliable message delivery. It's the foundation infrastructure for most messaging solutions.

Q: Remote procedure call (RPC) also allows one program to communicate with another in a network. What are MOM's advantages and disadvantages versus remote procedure call?

A: RPC is good for straight, inside types of departmental applications because RPC is inherently synchronous. MOM is inherently asynchronous, which makes it much better than RPC for distributed computing. What this means is that MOM will store a message in a queue, and hold it to be delivered if the recipient application is down or otherwise not ready to receive the message. With RPC, you have to be ready to accept the message the moment it's sent. If there's any break in the action, the message is gone. Disadvantages to MOM can come in the data transformation stage - to translate the message from one application to another. This is usually done through adapters or other component technologies. This problem will likely be obviated by upcoming Web services such as J2EE, SOAP and others. MOM will still be an important foundation to enable these services.

Q: What types of MOM products are available?

A: Products range from simple to complex, and companies can apply one or more, depending on their needs. It's fairly common for the largest companies, especially, to mix and match different middleware products for different needs. There can be standalone MOM, or MOM that's bundled in with an integration platform. If you're doing sophisticated business process management or if you want to implement B2B successfully across multiple organizations, you need a very robust messaging infrastructure such as IBM's MQ Series or Tibco's ActiveExchange or ActiveEnterprise. In Europe, Software AG's EntireX is very popular. Some messaging products are folded into more complete application integration solutions where you can do both messaging and data transformation. Products here are available from WebMethods, SeeBeyond (formerly STC) and Vitria.

Q: Where are the issues, problems or hot spots with MOM?

A: Middleware can be expensive, and not everybody's skilled at working with infrastructure products. Implementing MOM takes thought - you have to have some systems architecture design up front. Training internally is a good idea. Once it's up and running, it's okay. But it's not something you can buy off the shelf and snap in. To figure out how heavy or lightweight a solution you need, you need to have a good idea of what applications are in your enterprise and what's going to be added to your enterprise through acquisition or collaborative working arrangements.

Ambrosio is a freelance writer in Marlborough, Mass. Reach her at jambrosio@mediaone.net.