Digital library mediators allow interoperation between diverse
information services.  In this paper we describe a flexible and
dynamic mediator infrastructure that allows mediators to be composed
from a set of modules (``blades'').  Each module implements a
particular mediation function, such as protocol translation, query
translation, or result merging.  All the information used by the
mediator, including the mediator logic itself, is represented by an
RDF graph.  We illustrate our approach using a mediation scenario
involving a Dienst and a Z39.50 server, and we discuss the potential
advantages and weaknesses of our framework.