Returning to Web software architecture of Figure 1, we now discuss services and applications. These are not clearly defined for services are essentially generic applications, and most applications are complex metaproblems [27] built recursively from services and ``sub-applications.'' Thus, there is a grey fuzzy line distinguishing services and applications. For this paper, we have chosen seven applications discussed in Sections 4.2 and 4.3, which we relate to the five services described below.
This includes all the base WebWindows functionalities that we have already discussed.
This includes base database storage, management, query, and dissemination of the full range of multimedia archives of the World's distributed digital libraries. As already discussed, we can expect hundreds of Terabytes of available information dominated by video data. Note simulation---such as access on demand to a weather model---is included in this service.
This collection of services enables electronic commerce, including on-line banking and shopping. These services are also essential for the use of the WWW for processing and exchange of proprietary data.
This includes desktop video conferencing, three-dimensional graphics MOOs, geographically distributed CAVEs leading to full televirtual interactions. As discussed earlier, a wide variety of other types of interactive information exchange is necessary. This underlies the concepts of collaboratories (virtual research groups or scientific laboratories), and the virtual company of the next century's agile manufacturing environment. In the more static mode, we see workflow and configuration control (cf. Figure 12, which allows tightly integrated projects, such as those to build a complex system such as an aircraft (see Section 4.3) or a large software module with a distributed team (Section 4.2(f)).
This service can be used to control remote medical and scientific instruments; search the world for information; or link computers in different companies for a multi-disciplinary optimization of a new vehicle.
Some services listed above can be already prototyped in terms of today's Web technologies, for example base WebTop or early Collaboration services. Some other services are still waiting for their pervasive enabling technologies, such as physical infrastructure that will enable InfoVISiON or security that will enable Internet Commerce. Finally, the computationally extensive NII services, characaterized above broadly as ``Metacomputing'' require a major extension of the whole Web paradigm, currently still focused on static page services, but already gradually expanding towards computation and interactive simulation via technologies such as Java, or WebWork discussed in Section 3.4. Based on current and emergent Web technologies discussed in Section 3, we can start looking into the future to envision the coming generation of critical NII applications and high level services discussed in the following section.