We envisage an architecture for the NII, shown in Figure 2 that builds applications on top of general (multi-use) services, which themselves ride on a collection of technologies, and middleware, which we term generically WebWindows, and discuss in Section 3.
Figure 2: A layered view of Web (NII) software building applications on
top of generic services that are in turn built on pervasive
technologies
In Table 2, we list some important pervasive technologies that will be critical building blocks of the future NII. This includes the basic hardware architecture where there is general agreement on the importance of ATM. Currently, ISDN is being deployed quite widely, and it will be important to see if this performance (128 Kbits/second) is sufficient to enable many NII applications. One to two megabits/second performance is needed for NTSC quality digital video with MPEG compression. However, either better compression (such as Wavelet) or quality reduction (smaller images) is sufficient for many applications, such as education (where small clips---not two hour movies are needed) and collaboration. The latter illustrates a typical NII/Web issue. There are several excellent video conferencing systems, such as Intel's Proshare for the PC. However, a good collaboration environment requires not just video exchange of the participants, but also common whiteboards and other text and graphics information exchange. The latter are clearly best implemented with Web technology, and I see that the days of stand alone collaboration systems are numbered---video conferencing will be integrated with the Web and then will evolve to a full televirtual environment embodying such technologies as VRML and MOO's---the most elegant multi-user virtual worlds. Other integration challenges are seen in the message passing arena where we should reconcile parallel processing technologies, such as MPI and PVM with MIME and HTTP of the WWW. Again, current relational database systems and the powerful but less structured WWW search engines have complementary strengths, which need to be integrated [8].
Table 2: Some important real world technologies that are (to be)
incorporated into the WWW.