In this paper we focus on the formalization of componentbased architecture self-reconguration as an action associated to qualityof-service (QoS) contracts violation. With this, we aim to develop on the vision of the component-based software engineering (CBSE) as a generator of software artifacts responsible for QoS contracts. This formalization, together with a denition of a QoS contract, forms the basis of the framework we propose to enable a system to preserve its QoS contracts. Our approach is built on a theory of extended graph (e-graph) rewriting as a formalism to represent QoS contracts, component-based architectural structures and architecture reconguration. We use a rule-based strategy for the extensible part of our framework. The reconguration rules are expressed as e-graph rewriting rules whose left and right hand sides can be used to encode design patterns for addressing QoS properties. These rules, given by a QoS property domain expert, are checked as safe, i.e., terminating and conuent, before its application by graph pattern-matching over the runtime representation of the system.