The wide adoption of the Z39.50 protocol from the Libraries exposes their abilities to participate in a distributed environment. In spite of the specification of a unified global access mechanism from the Z39.50 protocol, unsupported Access Points result to query failures and/or inconsistent answers. A challenge to this issue is to substitute an unsupported Access Point with others, so that the most similar semantics to the original Access Point can be obtained. In this paper we present the zSAPN (Z39.50 Semantic Access Point Network), a system which enhance the interoperability of the library search systems, by exploiting the semantics from the Bib-1 Access Point official specification of the Z39.50 information retrieval protocol. zSAPN substitutes each unsupported Access Point with a set of other supported ones, whose appropriate combination would either broaden or narrow the initial semantics, according to the user's choice.