This document specifies a web service interface based on JSON [1] and XML [2] for transporting over the Internet or an extranet network a set of ontological data conformant to IEC 62656-1. This web service allows an exchange of data parcel(s) between a parcel server and a parcel client or between parcel servers. The data parcel(s) used therein comprises one of the parcel ontology layers, i.e., Axiomatic Ontology layer (AO), Meta-ontology layer (MO), Domain Ontology layer (DO) or Domain Library layer (DL), the detail of which is defined in IEC 62656-1. This interface comprises three basic services, registration service, resolution service and subscription service. With respect to query, the query language for a data parcel will be a subject of another part of IEC 62656. Consequently, the web service interface specified in this document includes the following; detailed specification of the three basic services; transport methods of data parcel(s) used in ontology data communication. The following items are outside the scope of this document. user identification and authorization query language; data and communication security techniques.