Research is built upon assumptions since not everything needed to move forward is known. "One must assume something to learn something." "The more assumptions or the stronger assumptions that one makes, the more one insures that her analysis will yield clear-cut and interpretable results; at the same time, the researcher, more than the empirical observations or records, is determining these results."
All research is built upon assumptions. We are limited in what we can test at one time. Some variables may not be measurable until later.
An assumption is a realistic expectation. It is something that we believe to be true. However, no adequate evidence exists to support this belief. An assumption is an act of faith. It will not be tested in your research.
If critics can dismiss your assumptions, then your research is not likely to be taken seriously. Thus, assumptions must be identified and considered with care.
Assumptions listed in research papers is often a good source of research topics.
Under the tradition/convention used by researchers, the researcher is responsible for informing the reader of important assumptions made. If the reader cannot accept these assumptions as reasonable, there is little point in reading the rest of the research report.
Only important assumptions are identified and listed. For example, you would not list as an assumption that your statistical software is accurate. Ordinarily, assumptions are simply listed unless they are especially important, controversial, or unusual. In that case, they may be discussed.
In a citation analysis study, you assume that the citation is evidence of use and that use is reflected in the citation. In a user study, you might assume that respondents are truthful and knowledgeable. Or is this so obvious and reasonable, that you don't state this assumption?