FUCHS@EMBL.BITNET (Rainer Fuchs (EMBL)) (09/21/89)
(I repost the following because our Bitnet connection might have been down
the first time; so excuse me if you get this twice)
We are interested in installing some kind of conferencing/news system at our
site, but need some more information about the different programs available.
We currently have News v5.6 but what we miss is a topic/reply system for
easily following the course of a discussion (like in VAX notes).
So my questions is:
Do the newer versions (>5.6) have such feature? And generally, what
are the differences to v5.6 (only bug fixes or new features) ?
Thanks
Rainer Fuchs
EMBL Data Library
European Molecular Biology Laboratory
Heidelberg, FRG
Bitnet/EARN: fuchs@emblgih900@UUNET.UU.NET (Geoff Huston) (09/22/89)
Rainer Fuchs writes:...
>We currently have News v5.6 but what we miss is a topic/reply system for
>easily following the course of a discussion (like in VAX notes).
>So my questions is:
>Do the newer versions (>5.6) have such feature?
This is probably worth a few paragraphs explaining how NEWS works and why
topic/reply systems are very difficult under the USENET system.
Firstly a few words about VAXnotes: VAXnotes is a centralized system. When a
user opens a VAXnotes conference on a local system the VAXnotes application
opens a DECnet connection to the nominated (single) server for that conference,
and all items are passed across the wires on demand to the reader. All postings
made into that conference are fed into the server for that conference. With
this model, when a read session is opened, then the reader is able to view all
postings made into that conference up to that point in time. All postings as
replies are tacked onto the end of a linear reply list in time order. The
problem with this model in the larger network environment is the absolute
reliance on the availability of the server and the availability of the network
to allow the live connection from the user to the server.
The USENET news model is fundamentally different. NEWS uses a flooding
mechanism to deliver postings to every site receiving the conference. The
reading operation is now NOT a network tyransaction: the items are stored
locally, and all postings are made into the local system. The NEWS transport
system is responsible for flooding all local postings to its neighbours, who
flood in turn to their neighbours, etc. The outcome of this mechanism is that
readers on two different systems will NOT see the same time ordering of items,
due to the propagation dealys inherant in this flooding technique.
The impact of this flooding on the topic / reply system is that conversations
are no longer a linear chain of topic and a list of replies in time order (and
with the additional assumption that a reply within the list has been made after
the reader has viewed all previous reply notes before making the next posting
into the conversation). The USENET model is much closer to a tree structure,
where conversations tend to widen out as a number of readers all make replies
to a single item, and so on.
As well as this alteration of a linear list into a tree there is also the
context information within the posting which sites the item into a particular
position in a conversation tree. The USENET standard includes the use of the
References: line which is a list of the message ids of the parent item to which
the posted item is posted as a reply, concatenated with the parent's reference
chain. In essence the tree as presented to the news system is a tree
constructed by BACKWARD pointers. An additional complication is that the tree
may not be complete - NEWS systems retire and delete old messages as a
continual operation, and often replies arrive on a system before the item
referred to by the reply, so the tree is not only a backward pointer tree, but
nodes within the tree may be missing. Just to further add to the problem whan a
newsgroup also has an associated mailing list, many postings within the
newsgroup, although they are replies to previously posted items, do NOT contain
the References: header line of backward pointers.
Now the reader of NEWS would like to view each conversation as a linear chain
of topic and posted replies / followup messages. The issue is how to convert a
backward referenced tree into a forward singly linked list, and also how to
sensibly make automatic decisions that an item which does not include backward
references is actually a logical component of a conversation stream.
I have mucked around with this for some time, and have come up with prototype
solutions which are invariably very complex, and consume large amounts of CPU
time, both in the initial inclusion of an item into the local database, and on
the part of the reader.
The current NEWS facilities are backward chain following (READ/PARENT) and
forward conversation selection (READ/FOLLOWUP). To make the execution of these
commands realtively efficient, the backward movement is based on a lookup of
the item referenced through the References: header, but the forward movement is
made by a simple textual comparision of Subject: headers.
To summarize this area, you cannot reproduce the Topic/reply model of VAXnotes
in a reliable and useable manner unless you also adopt the model of centralized
(single) network servers for each newsgroup. Within the USENET this simply is
not feasible. (I must make a reference to a gateway that exists between a
USENET conference and VAXnotes which I have used in the past - the way in which
the gateway handeled the Topic/Reply problem was to eliminate replies
altogether, and make each USENET posting a new topic.)
So in answer to the original question - no - NEWS is not going to do much more
than it does at present in the topic/reply area. If thats what you are after -
then buy VAXnotes!
Geoff Huston
gih900@csc.anu.oz.auMats.Sundvall@bmc.uu.se (09/25/89)
In article <8909212313.AA14866@uunet.uu.net>, munnari!csc.anu.oz.au!gih900@UUNET.UU.NET (Geoff Huston) writes: > Rainer Fuchs writes:... > > > Firstly a few words about VAXnotes: VAXnotes is a centralized system. When a > user opens a VAXnotes conference on a local system the VAXnotes application > opens a DECnet connection to the nominated (single) server for that conference, > and all items are passed across the wires on demand to the reader. All postings > made into that conference are fed into the server for that conference. With > this model, when a read session is opened, then the reader is able to view all > postings made into that conference up to that point in time. This also make it similar to Usenet News in the sens that you hook up postings to a linear list that was sampled some time ago. All other users that may reply to the same item may or may not have your replies in their list. If they sampled the database BEFORE you updated the database they will not have them available. The only difference is the amount of time it will take until you get the "complete" reply list. > All postings as > replies are tacked onto the end of a linear reply list in time order. Is it possible to use the timestamp to order entries? If you assume that all nodes have a valid timestamp and a valid timezone header line you could use this to order entries. Sure DEC has to do something similar with postings into VAX Notes. I have never used VAX Notes but as you describe it they rebuild a tree into a linear list. The information you lose may not be that big in a small conferense but in a worldwide VAX Notes conference you would loose a lot. > The > problem with this model in the larger network environment is the absolute > reliance on the availability of the server and the availability of the network > to allow the live connection from the user to the server. > > > So in answer to the original question - no - NEWS is not going to do much more > than it does at present in the topic/reply area. If thats what you are after - > then buy VAXnotes! > > > Geoff Huston > gih900@csc.anu.oz.au I hope you are wrong. If Usenet News is going to survive it will have to evolve. This is one of the areas where it need improvements. -- Mats Sundvall Biomedical Center +46/18174583 University of Uppsala Mats.Sundvall@BMC.UU.SE Sweden psi%24020019700620::MATS
gih900@UUNET.UU.NET (Geoff Huston) (09/26/89)
Following on with this topic about the differences between the USENET NEWS
model and that used by VAXnotes:...
Mats Sundvall writes:
>This also make it similar to Usenet News in the sens that you hook up postings
>to a linear list that was sampled some time ago. All other users that may reply
>to the same item may or may not have your replies in their list. If they
>sampled the database BEFORE you updated the database they will not have them
>available. The only difference is the amount of time it will take until you
>get the "complete" reply list.
but you will NEVER get a "complete" reply list (unless the newsgroup is very
inactive) - new postings are being added continually.
>Is it possible to use the timestamp to order entries? If you assume that
>all nodes have a valid timestamp and a valid timezone header line you
>could use this to order entries.
Have you looked at the timestamp fields in the headers? They are a mess!!!!
Even if a program could make some sensible effort at translating the ascii
timestamps into a binary post date, the information doesn't help - the
asychronous nature of USENET postings makes efforts at linearizing a
conversation of limited value.
> Sure DEC has to do something similar
>with postings into VAX Notes. I have never used VAX Notes but as you describe
>it they rebuild a tree into a linear list. The information you lose may not
>be that big in a small conferense but in a worldwide VAX Notes conference
>you would loose a lot.
VAXnotes does not have to rebuild a tree into a list: as all postings within a
conference occur on the node hosting that conference there is a unique time
order of postings into the conference. USENET does not have that ability.
>> So in answer to the original question - no - NEWS is not going to do much
more
>> than it does at present in the topic/reply area. If thats what you are after
-
>> then buy VAXnotes!
>
>I hope you are wrong. If Usenet News is going to survive it will have to
evolve.
>This is one of the areas where it need improvements.
Its a big problem - part of the assets of the USENET network is the ability to
use a wide range of network tools to distribute news - mail, ip connections,
DECnet, X.25, and anything else at hand. The diversity of NEWS platforms and
the diversity of systems and networks certainly presents challenges - the task
for each NEWS implementation is to be able to correctly interpret data that is
fed to it, and feed data to adjacent NEWS sites in a format which is as
reasonable as possible (this implies adherance to the RFC, certainly, but also
the conservative use of additional functions in other implementations (e.g. the
Supersedes: header interpretation).
Any topic/reply tree construction implementated by a NEWS system is going to
have to fit within this USENET environment. By camparison Digital's VAXnotes
was easy - one platform - one implementation - one network architecture. USENET
NEWS faces a much more significant set of challenges!
Geoff Huston