Abstract: The support of existing software applications for construction cost estimation (CCE for short hereafter) for the specifications for CCE (CCE specifications for short hereafter) mostly depends on the estimators' manipulation in a large extent. Therefore, the proficiency of the estimators on CCE specifications greatly affects the efficiency and accuracy of CCE. In addition, the existing software applications cannot adapt well to the change in the CCE specification. Ontology provides a potential approach to establish a computerized and flexibly extendable representation of CCE specifications. In this paper, based on the analysis of a typical CCE specification, an ontology-based representation of CCE specifications is established. Then, an ontology-based framework for expressing and automatically utilizing CCE data is formulated and the generality of the framework is illustrated. The representation and framework lay a sound foundation for automatic CCE.