Network-Based Interaction
Alan Dix

Note to The Reader from Alan
I am a terrible scholar in the sense that I remember things, but often not where they come from. If you know of key references (paper or electronic) to things covered in this outline, please let me know.

1. Introduction

   In some ways this chapter could be seen as redundant in a HCI book - surely networks are just an implementation mechanism, a detail below the surface, all that matters are the interfaces that are built on them. On the other hand, networked interfaces, especially the web, but increasingly also mobile devices, have changed the way we view the world and we view society. Even those bastions of conservatism, the financial institutions have found themselves in sea-change and a complete re-structuring of the fundamentals of businesses ... just an implementation detail.

   structure

   The chapter will begin with a brief overview of types of networks and then deal with network-based interaction under four main headings:

   • networks as enablers
     things that are only possible with networks
   • networks as mediators
     issues and problems because of networks
   • networks as subjects
     understanding and managing networks
   • networks as platforms
     algorithms and architectures for distributed interfaces

   In addition, there will be a section taking a broader view of the history and future of network interaction and the societal effects and paradigm changes engendered, especially by more resent developments in global and wireless networking.

2. About Networks

   This section will briefly review the types of network currently used and coming on stream. As an aid to seeing the broader issues surrounding potentially ephemeral technologies, it will use the following two dimensions to classify them:

   • global vs. local
     How spatially distant are the points connected - ranging from machines in the same room (IrDa, bluetooth), through those in a building/site (LAN) to global networks (Internet, mobile phone networks)
   • fixed vs. flexible
     This is almost, but not entirely terrestrial vs. wireless (fixed networks increasingly involve wireless links). More a matter of the mobility of devices and the rate of reconfiguration of the network.

   On the whole we have seen in the last 10 years the main focus of network-based interaction has moved anti-clockwise in this picture from fixed/local networks (mainly LAN), through fixed global networks (the Internet and web explosion), through global mobile networks (mostly phone-based, but including WAP, i-mode etc.) and moving towards flexible local connections between devices.

3. Networks as Enablers
   things that are only possible with networks

   It can be the case that the network is no more than an implementation detail - for example, using a networked disk rather than a local one. However, there are also many applications which are only possible because the network is there, for example video-conferencing. The key feature of networks is the access to remote resources of some kind or other.

   remote resources

   Four kinds of remote things made accessible by networks:

   • people
     networks means we access, synchronously or asynchronously other people, either directly (e.g. email, video-conferencing,) or indirectly (e.g. recommender systems)
   • physical things
     We can also view and control remote things (e.g., web-cams on public places, remote control of telescopes in tropics (see HCI'94))
   • data
     Sometimes, data is stored remotely purely for convenience, but often data is necessarily stored remotely: because it is shared by many remote people, because reasons of control, security or privacy demand remote storage, because it is used by a single user at different locations (web email), or because it is too extensive to be stored remotely (e.g. large databases and fat client/server)
   • computation
     Sometimes it is remote computational resources accessed over the network as in thin client and ASP (application service provider) applications.

   applications

   Application areas enabled by networking will mainly be covered in other chapters. Where this is the case, this chapter will merely identify them and any specific network related features and cross-reference to relevant chapter.

   Applications include: groupware, mobile computing, ASP/thin client, global information/the web, e-commerce, virtual organisations, telecommuting, network community, e-democracy. [[reader: tell me more!!]]

4. Networks as Mediators
   issues and problems because of networks

   This section takes as a starting point that an application is networked and looks at the implications this has for the user interface. This is most apparent in terms of timing problems of various kinds. This section is really about when the network is largely not apparent except for the unintended effects it has on the user!

   network properties

   bandwidth, latency, set-up time etc
   reliability, buffering, cost
   connection-based vs. datagram
   QoS, jitter, compression, loss

   These are quite technical issues and will be dealt with briefly, but in sufficient detail to allow the appreciation of their user interface implications.

   UI properties

   network transparency ... general concept ... good or bad (e.g. CSCW critique)

   delays and time - reference out to literature on temporal issues and other chapters where these get covered. literature on web delays, estimation of delays for progress feedback etc.

   effects on spoken conversation of long delays, half-duplex channels etc.

   consistency (and lack of it!), race conditions

   timeliness of feedback/feedthrough

   awareness of other people

   media issues

   delay/dropped packets: different seriousness of this for sound/video

   broadcast vs. interaction: pre-processing, jitter/buffering/delay tradeoff

   examples: streaming video/audio, web-radio, video-conferencing

5. Networks as Subjects
   understanding and managing networks

   Here we look at issues that arise in the explicit management of the network and issues that arise due to its intrusion and 'breakdown' situations.

   network models

   This parallels the 'network properties' part of the preceding section, again covering technical issues at a level sufficient to understand their effect on the user.

   The chapter will look at layers (reference OSI, but use Internet as better known example), addressing, 'yellow/white pages' issues, routing and concepts of internetworks in general as well as the Internet

   network management

   large scale network management - briefly mention, this is a specialised and complex area, but relatively understudied in the HCI literature [[reader tell me if you know good examples]]

   small-scale/end-user management - e.g. location manager in Mac, networked printers etc. [[reader: I'm aware of studies of user models of networked printers etc., if you know where thus is reported please tell me!!]]

   network awareness

   understanding costs, etc.

   network/resource awareness

   feature interaction (doesn't really fit here, but not quite sure where to put it!!)

6. Networks as Platforms
   algorithms and architectures for distributed interfaces

   user interfaces are hard enough to construct on a single machine, concurrent access by users on networked machines is a nightmare!

   Appropriate algorithms, architectures, toolkits and frameworks can help ... a bit.

   locking

   traditional and more lightweight forms applied in groupware

   optimistic concurrency

   algorithms for distributed (text) editing dOPT etc.,

   asynchronous replication mechanisms (Notes etc.)

   architectures for networked systems

   web arch, mobile arch, PoP

   supporting infrastructure

   awareness servers, notification servers, event/messaging systems

   discovery (JINI, UPaP)

   mobile code, intelligent networks etc.

7. History, Futures and Paradigm Shifts

   [[possibly history ought to go earlier in chapter?]]

   history

   development of the Internet and web

   early applications NLS etc.

   paradigm shift

   global village, trans-national markets, popular views of cyberspace

   differences between countries and cultures

   effects of charging models (e.g. mobile phones: US vs. UK vs. Japan)

   permanent connectivity - being connected vs. becoming connected (I've previously called this PopuNET)

   futures (near)

   short range networking - ubiquitous networks

   next-generation networks - support for media & data

   IP-vX or mobile standards on fixed lines?

   plus ....