Software companies have typically used Fully-Exposed APIs and customized, proprietary solutions to try and achieve this integration.
This makes perfect business sense: The tighter the integration, the harder it is to replace the software. Furthermore, this is usually just the first step. Once integrated, software companies will always try to move further up the customers value chain. In the SOA landscape, this presents a real dilemma. As Joe McKendrick at ZDNet points out:
How do vendors sell a concept that will make it easier for customers to drop their products? What's in it for them? The benefit of SOA is that services can be swapped out almost on demand. This, of course, is one of the conundrums vendors face, especially those pushing SOA in a big way. (Of course, all vendors say they are about "SOA" these days, right?)This is a pretty interesting point. If loose-coupling is perfectly achieved, the software becomes perfectly replaceable.
For software consumers, this is great news. It means that companies will need to compete on features and price rather than on how well they can entrench themselves in our landscapes.
For those of us in software, it means we'll have to step up our games and learn to compete in the SOA environment.