  XML Schema is the language used to define the structure of messages exchanged
between OGC-based web service clients and providers. The size of these schemas
has been growing with time, reaching a state that makes its understanding and
effective application a hard task. A first step to cope with this situation is
to provide different ways to measure the complexity of the schemas. In this
regard, we present in this paper an analysis of the complexity of XML schemas
in OGC web services. We use a group of metrics found in the literature and
introduce new metrics to measure size and/or complexity of these schemas. The
use of adequate metrics allows us to quantify the complexity, quality and other
properties of the schemas, which can be very useful in different scenarios.
