The majority of the queries/questions that LIS personnel will have to deal with are about subjects. An answer to such a query, in whatever form it may finally be presented to suit the requirements of the reader, will be derived from the subjects embodied in documents. Therefore, the LIS personnel should become familiar with the subjects they have to deal with predominantly. The more intensive the knowledge they have of the subjects, the more helpful it will be in making the information services productive.
Obviously, such a knowledge of all the subjects cannot be acquired by one person. A person with a basic background in a subject - say, at the graduate or post-graduate level - can build upon it through experience, - such as doing research and/or teaching the subject, But the LIS personnel's work does not admit of doing research simultaneously (other than in library and information science). Further, it is not the intensive specialisation in a narrow region of a subject that will be useful in the work of the LIS personnel. What they require is a broad perspective that is, the highways and byways of the different subjects with which their clientele are concerned.