With the development of information science and information society, an increasing number of information on the internet is stored in XML format. Given the fact that XML is becoming the standard in exchanging and representing data, how to extract accurate information in an effective and efficient way from XML documents has become an important issue arousing much interest of researchers. For any research oriented novel effort, the analysis of existing systems and respective in depth knowledge exploration is of great significance. The number of research methods are implemented in the field of information retrieval for keyword search on semi-structured data and these researches possesses certain strengths as well as limitation. Hence, understating the existing research for its respective strengths as well as weaknesses, the scholar can get better insight of the technologies and approaches to achieve optimal solution. Thus, taking into consideration of these requirements, in this chapter of the presented thesis, a number of literatures have been explored and studied for keyword search on semi-structured data.