This paper investigates the evolution of the end-to-end data system and in particular what constitutes a data system in today's rapidly evolving environment of distributed data system components. Particular attention is devoted to the role of the data system integrator, a computer program or set of programs that may run on the user's computer or at a remote site. By integrating data discovery and delivery with the user's analysis environment, the data system integrator provides the user with seamless access to remote data archives from his or her visualization or analysis program. The data system integrator is the component that effectively defines the data system in an environment in which system components are being produced independently by a broad range of data and service providers. What makes the data system integrator possible is the adoption of a relatively small number of data access protocols, metadata descriptions and data set directories. At the same time, the lack of convergence on one data access protocol, one directory access protocol, and one metadata standard is what necessitates the data system integrator. The data system integrator provides the multiprotocol glue necessary to achieve interoperability over a broad range of service providers. The OPeNDAP Data Connector (ODC) is discussed in detail as an example of a data system integrator designed to run on the user's computer. The requirements of the various functional elements of the system integrator are described, and it is shown that the system integrator is by necessity a multiprotocol program.