There is increasing interest in having software systems execute and interoperate over the Internet. Execution and interoperation at this scale imply a degree of loose coupling and heterogeneity among the components from which such systems will be built. One common architectural style for distributed; loosely-coupled, heterogeneous software systems is a structure based on event generation, observation and notification. The technology to support this approach is well-developed for local area networks, but it is illsuited to networks on the scale of the Internet. Hence, new technologies are needed to support the construction of large-scale, event-based software systems for the Internet. We have begun to design a new facility for event observation and notification that better serves the needs of Internet-scale applications. In this paper we present results from our first step in this design process, in which we defined a framework that captures many of the relevant design dimensions. Our framework comprises seven models-an object model, an event model, a naming model, an observation model, a time model, a notification model, and a resource model. The paper discusses each of these models in detail and illustrates them using an example involving an update to a Web page. The paper also evaluates three existing technologies with respect to the seven models.

Persistent, dynamic references (or links) to remote documents are an essential part of an online library. This thesis examines two distributed database systems, X.500 and the Domain Name System (DNS), upon which to build dynamic references. DNS was chosen and was used to design a model and build a sample dynamic reference system. This system seems to exhibit the scalability, robustness, usability, and efficiency necessary for building global distributed online libraries.