This thesis introduces similarity measures to be used by comparing XML workflows and RDF or OWL structures. These structures are accessed and converted into a generic graph representation. Two graphs are compared by a measure to conclude in a single value indicating the similarity of the graphs. Similarity is calculated by two different similarity measures, the graph isomorphism measure and the subgraph isomorphism measure. The graph isomorphism measure detects structurally identical graphs and calculates the similarity upon the nearness of the node labels. Structurally different graphs are compared by the subgraph isomorphism measure to find matching parts. The size and the label similarity of the nodes of a matched part contribute to its similarity based upon the compared graphs. The highest similarity value of all parts is defined to be the similarity of the two graphs. Performance improvements were developed and implemented which led to a decreasing runtime. Further improvements were analyzed and proposed to be implemented at a later date.