The paper introduces the SILK tool-set, a tool-set based on constraint logic programming techniques for the support of application
integration. We focus on the Integrator component of SILK, which provides tools and techniques to support the process of model
evolution: unification of the models of the information sources and their mapping onto the conceptual models of their user-groups.
We present the basic architecture of SILK and introduce the SILK Knowledge Base, which stores the meta-information describing
the information sources. The SILK Knowledge Base can contain both object-oriented and ontology-based descriptions, annotated
with constraints. The constraints can be used both for expressing the properties of the objects and for providing mappings
between them. We give a brief introduction to SILan, the language for Knowledge Base presentation and maintenance. We describe
the implementation status of SILK and give a simple example, which shows how constraints and constraint reasoning techniques
can be used to support model evolution.