A core challenge of SOA, after all, is building for change. If you had good reason to believe today's requirements were permanent, you probably wouldn't bother with the expense and complexity of SOA.
What, then, is your metarequirement of agility? As we also detail in our book, it doesn't make sense to expect that the IT organization would be capable of building systems that could deal with entirely arbitrary change, since such a requirement would be prohibitively expensive to satisfy. Instead, each organization will have to decide for itself precisely how much they can invest in order to achieve the level of flexibility they require their SOA implementation to have. While deciding on your agility metarequirement is an essential part of your SOA planning, even more important for the long-term success of your SOA initiative is in ensuring that your SOA implementation conforms to that metarequirement over time. In other words, guaranteeing that your SOA meets the needs of the business over time is a core measure of quality, and as such, SOA quality assurance must address the metarequirement of agility.
