Service-oriented architectures become popular by promoting the
use of web services for systems integration, but do not address the
issue of exporting semantically meaningful database functionality.
Existing solutions simply associate with each exported query a web
service with typed input and output parameters. The Query Set
Specification Language (QSSL) publishes web services, which expose a
set of supported queries against a database, as well as the schema
they are executed against, in a concise specification. QSSL describes
large sets of parameterized tree pattern (subset of XPath) queries,
without requiring exhaustive enumeration of them. QSSL enriches a WSDL
specification to form a specialized type of web services.
QSSL is particularly useful in integration scenarios, where
participating sources typically export limited query capabilities,
either for business reasons, security constraints, or technology
limitations. Moreover, QSSL makes the relationship between the input
and output types explicit by exporting the query statements and the
underlying schema, thus facilitating mediators that exploit the
capabilities of the underlying sources to answer user queries.