Jiri’s Notepad

When reading Jon Udell, I am sometimes surprised by ease with which he can explain very complex topics. Like in the following article excerpt on SOA an metadata:

As we weave more and better metadata into software, documents, Web sites, and file systems, the information stored in these various containers will become more available, more cohesive, and therefore more useful. The next challenge is how — in this new era of interconnected systems, people, and business processes — to unite these separate realms.

The solution is a complex recipe, but we can find many of the ingredients at work in the emerging discipline of SOA (service-oriented architecture). We use metadata to describe the interfaces to services and to define the policies that govern them. The messages exchanged among services carry metadata that interacts with those policies to enable dynamic behavior and that defines the contexts in which business transactions occur. The documents that are contained in those messages and that represent those transactions will themselves also be described by metadata.

There’s no overarching schema for the metadata that flows through the service network, touching routers, registries, security gateways, databases, and end-user applications. And, in view of its many forms and uses, it’s not clear that convergence on a single standard is necessary or even desirable. What is necessary is that within each metadata domain we strike healthy balances between the constraints we apply to metadata vocabularies and the evolutionary freedom we allow them. Across domains, we’ll speak the lingua franca of data and metadata, namely XML.