Therefore you need to make sure the tools used to facilitate these services are as usable as possible. A usable service will reduce the time you spend describing how to use the service and provide the patron with more time for analysis and synthesis. Consequently, it will reduce your costs as well as your patron's. In turn, this will improve the patron's perception of the library, and you will have time to explore ways to improve other library services. If you want to measure the usability of your library systems, then you first need to create a list of goals or tasks the system is suppose to allow users of the system to accomplish.
Goals are broad objectives broken down into smaller, discrete tasks.
For example, a goal might be for the user to print a list of book titles from your catalog pertaining to a particular subject. The characteristics of your user group can tip the outcomes of the usability study. People with physical impairments of some sort may encounter one set of problems, infrequent users of your system will have other sets of problems, lesser educated people will have yet another set of problems, and last but not least, people of differing cultural backgrounds will uncover further difficulties. It almost seems hopeless. At the same time, understanding all the differences in your user populations will force you to articulate policies and tailor your services accordingly.