Service interface description is one of the most important problems in service-oriented software architecture, and formal description methods are considered to be a promising approach for service interfaces. However, the existing interface models do not support transaction information description. By extending the model of Web Service Interface, this paper presents an interface model that can capture transaction information by means of fault handling and compensation. In this model, service interfaces can be specified at the signature, conversation and protocol levels. At each level, the compatibility and substitutivity are described formally. Furthermore, the interface specifications and corresponding verification methods are also presented at the conversation and protocol levels. The model supports precise transaction information description as well as flexible and effective verification for interface specifications.