Formal methods have been shown to be beneficial in increasing the quality of, and confidence in software systems. Despite the advantages of using formal methods in software development, the uptake in the commercial industry has been limited where the use of informal and semi-formal notations is favoured. To bridge the gap between the ease-of-use of semi-formal notation and correctness of formal methods, a number of approaches to the formalisation of informal and semi-formal notation have been researched and documented. Two of these approaches are discussed in this dissertation using a medium-sized case study to demonstrate the approaches. It was shown that each approach offered results that differed in terms of levels of abstraction, requisite knowledge of the formal target specification language and potential for automation.