Reusability always has been a controversial topic in Digital Library (DL) design. While componentization has gained momentum in software engineering in general, there has not been broad DL standardization in component interfaces. Recently, the Open Archives Initiative (OAI) has begun to address this by creating a standard protocol for accessing metadata archives. We propose that the philosophy and approach adopted by the OAI can be extended easily to support inter-component protocols. In particular, we propose building DLs by connecting small components that communicate through a family of lightweight protocols, using XML as the data interchange mechanism. In order to test the feasibility of this, a set of protocols was designed based on the work of the OAI. Components adhering to these protocols were implemented and integrated into production and research DLs. The performance of these components was analyzed from the perspective of execution speed, network traffic, and data consistency. On the whole, this work has shown promise in the approach of applying the fundamental concepts of the OAI protocol to the task of DL component design and implementation.