The original NewsWatcher fetches only Subject and Author headers
from the news server, and does so using the XHRD command which
must be given once for each header type. MT-NewsWatcher can obtain
much more information about articles, such as their posting date
and line count, so making decisions about which articles to read
easier for the user. However, this incurs an overhead in terms
of the time taken to download such information.
You can control whether MT-NewsWatcher needs to download header
in addition to the Subject header (which is always downloaded)
using the settings in the 'Subject window' panel of the preferences.
MT-NewsWatcher implements a new way of getting header information
from the server, using the 'XOVER' command. When this is activated,
fetching headers is usually much faster.
However, as explained below, downloading time is not a simple function
of these settings. This document explains how the various settings impact
What do those server options mean?
In the 'Server options' panel of the Preferences dialog, there
are a number of setting that determine how MT-NewsWatcher communicates
with your news server. Most of them have speed implications.
- Use XPAT command for searches
Searching article headers for a certain string can be performed
either by the news server, or by MT-NewsWatcher itself. If this
option is checked, searches are performed by sending an 'XPAT'
request to the server, which then responds with a list of matching
articles. Although this may take some time, the job of searching is
done by the server. If this option is unchecked, MT-NewsWatcher must
download all the headers for that group and search them itself, which
is much slower and requires more memory.
Nearly all servers support XPAT,
so you should turn this option on, and only uncheck it if the
server sends back an error message when you try to search.
- Use XOVER command to get headers
This is the main option that affects speed. When active, article
header information is downloaded in larger chunks, which is much
faster. It is described in more detail below.
Again, most servers support XOVER, so you should turn this on. Beware
that some servers may cause a warning message to be displayed
the first time you use it; the reason for this is described below.
- Don't open new connection when checking for new articles
Some servers return bogus article counts if you reuse an existing
connection to request group article information. In this case,
the client has to open a new connection to check for new articles.
This is not a problem with most servers, so this option should be
checked. If the 'Check for new articles' command never returns new
articles, you could try turning this option off.
- Don't send MODE READER command
Some servers require that news clients identify themselves as such,
by sending the 'mode reader' command (to distinguish them from other
servers with which your server exchanges news). Most don't, so you
should turn this option on.
- Allow up to N simultaneous connections
This controls the maximum number of concurrent connections to the news
server that can be opened. 4 is a sensible value.
More detail is given in the threading document.
What determines which headers are downloaded?
There are four settings that determine which headers need
to be obtained from the server. These are:
In summary, all headers which are either to be displayed, or filtered,
or used to build threads
are required from the server. If XOVER is active, then most information
will be contained in the response to the XOVER command, and additional
headers will only be required if they are not contained in the XOVER
data, which is described below.
- 'Subject window' preferences
- The three checkboxes in this preferences panel control whether or not
authors, dates and line counts are shown in subject windows. If checked,
this information obviously needs to be obtained from the server.
- 'Server options' preferences
- The 'Use XOVER command to get article headers' is the important
setting here; its workings are described below. If checked,
download time will not be affected by the choice of options in the
'Subject window' preferences.
- 'Thread using references' option
- This option, in the 'Newsreading options' panel, specifies that
MT-NW should attempt to build discussion threads based on the
contents of the References header. When active, Message-ID
and References headers are required from the server, because
they are needed to build the threads. Both these headers are
included in XOVER responses.
- The set of filters that apply to the group being downloaded
may also require that additional information be obtained from
the server. Extra headers will need to be downloaded if:
Of course, if more than one filter acts on an additional header,
that header only needs to be downloaded once.
- XOVER off
- The filter acts on a header that is not one of
those being displayed, as controlled by the 'Subject window'
- XOVER on
- The filter acts on a header that is not contained
in the XOVER data.
The XOVER command
When the news client (e.g. MT-NewsWatcher) requests XOVER
information for a set of articles, the server replies with a block of
data for each article that must contain the following headers:
|Date ||MT-NW converts this into your preferred date format
|Message-ID ||Needed for reference-based threading
|References ||Needed for reference-based threading
|Byte count ||Unused
|Line count ||
and which may (depending on your server type) contain this header:
|Xref ||Contains cross-posting information
Because this information is sent in big chunks, this is much faster than
fetching each of these headers independently. When receiving these
data, MT-NW processes them, discards information that is not required
either for display or filtering, and keeps the rest.
With XOVER active, almost all the information that you will normally need
for display, threading, and a basic set of filters, will be downloaded in
one go, which is fast. The exceptions are some older news servers which don't
include Xref information (which is useful for filters designed to catch
excessive cross-posting), and filters using the less common headers
like X-Mailer, and X-Newsreader.
Why do I a get a warning with XOVER?
When you activate XOVER for the first time, you may see a warning which says:
This news server fails to respond to a command which provides
information about the format of XOVER request results.
and gives you the options of either continuing at your
peril, or cancelling.
This occurs because your news server does not conform to some
recent specifications about the format of XOVER responses.
News clients are supposed to be able to get information
from the server on the content of XOVER responses by using the
LIST OVERVIEW.FMT command. MT-NewsWatcher uses this
to determine what to expect from an XOVER command. However, some
servers (notably those by Microsoft and the DNEWS server) don't
LIST command. In these cases, MT-NewsWatcher
assumes that such responses must contain the headers listed in the
table above, and if it finds Xref headers, it will use these as well.
But to warn you that it is making these assumptions (which might, for
some future server, fail), you will see this warning dialog. Hit
the 'Continue' button to continue to use XOVER with the assumed format.
MT-NewsWatcher stores those headers that it has downloaded for
a group until you close the subject window. If you edit a filter
and then re-filter the articles, new headers will only be downloaded
if you have created a new filter that uses a header not already
obtained for this group.