The use of the Unified Modelling Language (UML) during systems development has been growing in scale and complexity, often resulting in inconsistent specifications. In this paper we present a knowledge base goal-driven approach for consistency management of UML specifications represented as axioms, which define goals. We propose an inference procedure as a flexible pattern-based abduction used to build and morph paths based on the specifications. The approach involves a two-step interaction process between the specifications: observation and comparison. Prototypes of the knowledge base engine and of a tool to map UML specifications in XMI format to the knowledge base have been developed to demonstrate and evaluate the approach.