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While many organisations are re-engineering their architecture to exploit web services, few have yet moved on to build composite applications. This involves taking services from several sources and packaging them together as if they were applications in their own right.

A composite application can smoothly automate an end-to-end process, overcoming functional, departmental and technical boundaries. But they are difficult to build. Process-oriented integration companies such as Crossworlds (now part of IBM) and Asera (sold by its investors to Seec) had very limited succcess in the 1990. And while more standard EAI tools have also been used for this purpose, these are usually difficult, bespoke projects.

But the SOA now promises to provide an open, flexible platform for the creation of such applications. And suppliers such as See Beyond, BEA and IBM have all implemented successful customer projects.

Even so, most suppliers admit it is early days. Before any of this can happen on a large and cost-effective scale, suppliers of software packages must open up their processes - or their interfaces - in such a way that a composite application builder can make use of them.

This means two things: first, all existing, external interfaces must be 'wrapped' up as web services. This is a big job when there are hundreds of interfaces involved in even one module of an application.

And second, many previously internal processes, operating at a more granular level, also need to be exposed as services. This is a huge task, but until it happens, the range of composite applications that can be built will be limited.

"More than 90% of enterprise applications are monolothic. Their business logic is not externally accessible in a modular form that allows easy reuse in other applications," Gartner analyst David McCoy told the recent European Gartner Spring Symposium.

"Application vendors must open up their applications and interfaces more. But they are not holding back deliberately. It's market driven and it's in their interests," says Christopher Daerr, marketing manager for IBM's WebSphere products in Europe.

All the major suppliers have promised that this is happening, creating what has been called the SOBA (service-oriented business application). But how fast?

Of all the application suppliers, SAP has been the most vocal and active in its support for the SOA. Even so, says SAP's UK chief technology officer Simon Harrison, "Opening up SAP will take two, three, five, maybe even 10 years."

In spite of this, there is already something of a market in packaged composite applications. In 2003, for example, IBM announced five 'packaged' processes, customised for 12 different industries. These include, for example, managing accounts and transactions for retail banks and elecommunications companies.

"This is an automated process that sits on top of the underlying applications - it's a like a template," says Christopher Daerr of IBM. But is it really a package? For IBM, it is also an opportunity to sell the integrating middleware, such as WebSphere, and provide systems integration support. SAP, too, sells packaged composite applications in the form of xApps. These are automated, cross-application processes that run on Netweaver and make use of the underlying functions in MySAP, its business suite. So far, it has announced three xApps, with at least 10 more on the way.

Other suppliers have set out to build and sell similar composite applications - among them Commerce One and Siebel. But many of these automated processes are currently based on specific underlying packages, and might be perceived as packaged up best-practice from repeated systems integration engagements, rather than as standard packaged products.

For an independent market in packaged composite applications to become established, it may be necessary for these to become genuinely portable across different integration platforms and products. That means that the SOA platform itself must conform to open standards and all participating applications must only use standard web services interfaces. So far, few suppliers can demonstrate portability.

But the demand for packaged composite applications is unclear. Many will not want to use the same processes as a rival. Ram Menon of Tibco, for example, does not think there will be a market for packaged composite applications. "Is there a business for composite packaged applications? Yes - where government mandates processes that are simple. But I don't think there will be over a broad palate."