This makes the vast existing literature on information retrieval, its techniques and human factors, relevant to the net. However, this addresses only one aspect of computer-mediated communication, neglecting its function of supporting discourse within communities. Computer-based discovery, indexing and retrieval systems have a major role to play in that community, but are only one aspect of Internet information systems. These are complementary perspectives on the net in terms of its technological infrastructure, its communities of users, and their access to resources, respectively. At the top level the major net services are characterized in terms of their utility for access to resources or awareness of resources.
Access is sub-classified as to discourse, publications or services.
Asynchronous community discourse is sub-classified by whether the channel is slow or fast, and whether the community is centrally registered or not. Services are sub-classified by whether they are text or rich media. Web browsers such as Netscape are interesting in providing a single tool accessing nearly all the services shown except talk and chat. 4 A Punctuated Discourse Model of Computer-Mediated Communications Figure 1 presents a conventional model of Internet services in terms of their utility, but it does not provide an integrative model of the way in which they support communities. Such a model can be developed by noting that what distinguishes discourse from publication is that in discourse it is expected that the recipient responds to the originator, whereas publication is generally a one-way communication.