The Internet of Things consists of heterogeneous devices from a range of uncoordinated vendors, and this causes an interoperability problem. This thesis studies potential solutions to these challenges on the application layer of the Internet. Different approaches are studied, including, but not limited to: alliances, frameworks, consortia, open source projects, and closed projects. The thesis looks at three different strategies: standardization, code generation, and extending the current web. These strategies are discussed regarding the requirements of the Internet of Things as well as future prospects. Next, the thesis presents four approaches on how to include semantics in order to achieve interoperability. The study reveals that not all approaches are able to solve the interoperability issue, but some can. Based on the study, the thesis presents a tripartite division of the application layer. Protocols, data, and semantics are regarded separate problems that all require solutions in order to achieve an interoperable Internet of Things. This thesis does not provide a common language for the Internet of Things, but discusses the different requirements of such a language. The study provides guidelines on what need to be considered when developing an interoperable Internet of Things.