In this chapter, we survey and compare different ontology languages and tools with the aid of an evaluation framework. An ontology must be of high quality to enable actors to reach a common understanding of the domain at hand. The notion of “quality” in the context of ontology is discussed, and means to achieve high-quality ontologies are listed. The different quality aspects and means to improve them formulate the template for the comparisons of ontology languages and tools, which are two of the major factors that affect the quality of ontologies. The evaluation is based on both practical experiences and evaluations of existing ontology languages and tools. The authors believe that the discussions and understanding of the quality aspect of ontology will assist in developing high-quality ontologies in various application domains.