Virtual OPACs versus union database: two models of union catalogue provision

Z39.50 is often put forward as a means of providing a virtual union catalogue without the need for a physical union database. This paper considers some of the major technical and organisational issues involved in virtual catalogue production, contrasting them with the traditional union catalogue approach exemplified by COPAC. A way of integrating these two models of the union catalogue is suggested, which would allow effective service provision in the immediate future.