Provides the strategies for developing a valid subject heading structure in an online public access catalogue that relies on the machine-readable Library of Congress subject headings. The book is aimed at cataloguing specialists wishing to relate local solutions to the broader movement of information technology that aims to improve subject access to technical and scholarly material. Major issues of online authorities are raised: functions of a subject authority file; integration of LCSH-MR records into the local authority file; and accessibility of the multiple-subject heading arrays directed to users.