The sort of conference control system we are addressing here cannot be:
- Centralised. This will not scale.
- Fixed Policy. This would restrict the applicability. The important
point here is that only the users can know what the appropriate policies a
meeting may need.
- Application Based. It is very likely that separate applications will
be used for different media for the foreseeable future. We need to be able
to switch media applications where appropriate. Basing the conference
control in the applications prevents us changing policy simply for all
applications.
- Heterogeneity. Most existing systems have been fairly homogeneous. An
increasing requirement is for different systems to interwork. There needs
to be some basis for this interworking, at both the media data stream
level and at the conference control level.
- Difficult to get right. Writing distributed group applications that
interwork and tolerate network failures is difficult to get right.
Generally application writers either start from scratch, which means
re-implementing stock algorithms, or base their
applications on a scheme that promises to do everything, but in practice
turns out to be too inflexible.