Service Level Agreement (SLA) is gaining more and more interest since the dynamic aspect of the cloud computing can adversely influence the guarantee of the Quality of Service (QoS). Proving an SLA violation is considered to be a complex operation to the cloud consumer. This task gets more and more difficult to the consumers as they use services from multiple providers, each with its own monitoring policies. In order to implicitly help the consumer monitor the SLA and detect violations, it is necessary to implement some advanced SLA management strategies. Ontological representation and reasoning techniques in SLA management may be beneficial to the evaluation of the QoS. In this regard, we propose a monitoring approach with a new semantic SLA modeling for cloud computing. Our approach aims to help cloud consumers monitor the SLA documents and detect violations by considering the semantic meaning of SLA concepts and taking profit from the power of reasoning techniques. This maintains a reliable QoS and respects the SLA parameters. The efficiency and effectiveness of the proposed approach is demonstrated in this paper through a simulation and a case study.