Abstract
Although the process of semantic annotation of Arabic Web content is essential for the realization of the Semantic Web, the process of semantic annotation cannot be performed without an ontology suitable for the task. In this paper, we describe the design, implementation and evaluation of the SemTree ontology for lexical semantic relations. The ontology was evaluated for usefulness using a prototype system for lexical semantic annotation of Arabic text. Results of the evaluation indicate that the ontology was fit for the purpose of semantic annotations with lexical relations. The evaluation also reveled important recommendations for designing Arabic semantic annotation tools.