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Re: nexus

  • To: Multiple recipients of list <epc-l@iucr.org>
  • Subject: Re: nexus
  • From: Brian McMahon <bm@iucr.org>
  • Date: Fri, 6 Mar 1998 11:08:51 GMT
Dear Yves 

Thanks for your comments on the crystallographic neXus project. I'm glad
that we are now able to begin working on this. I am copying this response to
Lachlan, with a reminder that he can monitor our discussions at

> The basic idea is excellent. The aim is to distribute a number of data 
> available on the Web on a CD-ROM for those who have a poor or no access
> at all to the web.

Yes. However, it is also useful for people who have quite a good connection
to the Web, because even "quite good" can mean long and frustrating download
sessions if one is surveying many pages, or acquiring large software packages.

> Each time Lachlan make a reference he gives two links:
>  - the true URL
>  - the copy of the contents of this URL on the CD-ROM. Thus, whenever 
> possible, the user may report to the original information. This is a
> very clever idea.

For the constituency of web-connected users, it means that you can check the
"live" URL to see whether a more recent version of the software exists than
on the CD-ROM; if not, the CD-ROM version can be installed at once.

> The CD-ROM is divided in a number of sections
> + references of a number of institutions amd associations
> + scientific pointers
> + software

It is in some sense complementary to the SinCris and CWW lists of pointers
to other crystallographic sites. The major difference is that the neXus
collection mirrors the contents of the sites listed (in whole or in part).

> Obviously the contents is oriented towards Lachlan's primary interests. There
> are many references to mineralogy, powder diffraction and databases
> related to these subjects. The same is true for the software. No reference
> at all (or very few) to biocrystallography for instance.

Lachlan's primary role has been to collect and organise the information on
the CD-ROM, and to burn the many trial copies that he has produced. It's
entirely legitimate that the contents until now have reflected his own
interests and areas of expertise. It might make sense to build on his work
by recruiting other volunteers to manage collections in other areas of the
subject. Lachlan could be the mineralogy/powder editor and overall technical
coordinator; there would in time be other editors too. I think that at this
stage we can concentrate on getting the project fully operational within
Lachlan's selected topic areas; but he should give some thought to the
overall organisation to allow additional topics to be added in a modular
> The list of institutions has the same limitation: IUCr references are all
> included as well as a very limited number of crystallographic institutions.
> I do not know why other are not mentioned. For instance a reference is made
> towards the Synchrotron facility in Taiwan but not to the other ones.

In previous correspondence, Howard has raised doubts about the suitability
of including mirrors of individual institutions (such as the Cuban
laboratories). The problem is really one of selection (or, alternatively, of
finding enough filespace for an arbitrarily large collection of such
institutions). We will need to discuss in some detail the balance of
providing pointers to other external URLs (this is already well covered
within SinCris and CWW) and mirroring the contents of other sites, be they
national, regional or in some sense private pages.

> References are also made to some personal pages but I do not understand 
> how the selection has been made.

I would guess that the selection has been on the basis of Lachlan's
knowledge and editorial judgement. I see nothing wrong in that, though we
might consider a broader based editorial board in due course. We might also
expect that if the project really took off, individuals would be canvassing
for the inclusion of their own pages, so some sort of objective criteria for
inclusion should be drawn up.
> Thus I will conclude that Nexus is, for the moment, a good project, but 
> limited to some fields of crystallography and with a selection of pointers
> based on the personal interests of his author.

Let me outline the way in which I see the neXus project fitting into the
IUCr information web. Logically, we should have a directory tree mounted as
nexus-top which peers with iucr-top, cww-top and sincris-top. It will hold
the neXus pages that index other resources, and also the mirrors of the
individual software collections that have been acquired. The IUCr, CWW and
SinCris pages will be accessed by hyperlinks into the iucr-top etc
hierarchies. Hence the directory structure on my web server and its mirrors
will be:

           |             |            |             |
        iucr-top      cww-top    sincris-top    nexus-top

and it will be identical on the CD-ROM, but perhaps with an addition
higher-level introductory html page:

           |             |            |             |
        iucr-top      cww-top    sincris-top    nexus-top

In practical terms, Lachlan would maintain the nexus-top pages at Daresbury,
and I would mirror them on a daily basis at Chester (in the same way that
CWW is maintained in Geneva and SinCris in Paris). Lachlan would download
iucr-top, cww-top and sincris-top whenever he needs to press an up-to-date
disk. The mirror sites would download everything from Chester.

Do we all agree on this approach?


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