The extent to which the literature is identified and reviewed depends very much on the nature of the research. In a piece of higher degree research it is expected that no significant work will have been omitted from the candidate’s discussion of the literature and any such omission might seriously jeopardize a submission’s chance of success. It is therefore imperative that a full and thoughtfully designed search for literature be carried out. Masters dissertations are usually expected to cover all of the major work in a particular field and undergraduate research would be expected to discuss all the most prominent research. Professional research may not always need to cover the literature to same extent, it may be sufficient to provide context to the research by presenting the current situation. This will depend very much on the purpose and the audience of your research