- In the bilateral exchange model, materials are exchanged between two participating libraries. In practice, where such an exchange is found, the exchange rate is usually calculated upon a proportional basis, according to some agreed-upon value (e.g. one of one, two for one).
- The second model is a multilateral development of the first, and can be called, for convenience, the poling model. In this model, more than two libraries contribute to the draw from, a pool of materials.
- The third is called dual-service model. It is one in which two or more participating libraries take advantage of the facilities of one of the participants to produce a common output-for instance, a union list. The term “dual-service” is proposed both to distinguish this model from the next, and to emphasize the fact that all participants, including the facilitator, contribute to the common output.
- The last model is known as Service Center. The model is one in which a number of libraries employ the services of a facilitating participants to input the process materials for individual purpose rather than to the end of a common output. Hence, it is called the service-center model.
While the facilitator may be merely a service bureau, and not otherwise employ its own facilities, the model holds under the pricing conditions which will be stipulated for this type of co-operation.
Reference: Sujatha, G. (1999). Resource Sharing and Networking of University Libraries. Ess Ess Publications.