[DAS] pinging source

[Thomas Down]

On Tue, Sep 15, 2009 at 7:20 PM, Chervitz, Steve <
Steve_Chervitz at affymetrix.com> wrote:

> Andy Jenkinson wrote on 15 Sep 2009 10:04:03 -0700:
> >
> > I'm not sure if you meant the sources schema exactly as it is or to
> > make the <SOURCE> element  the root element. I would vote for the
> > former (i.e. a sources document containing one source). It makes
> > things much easier for the client and spec not to have a separate
> > schema.
> >
> > Regarding the XSL stylesheets, I can see where you're coming from. I
> > have some prototype stylesheets which have an option to show the XML
> > (prettied up), which I think is the best compromise.
>
> Optional stylesheets for web browsing sounds fine.
>
> On a related note re XSL: Stylesheets can also be used to communicate
> information to DAS clients, to control browser behavior with certain tracks.
>  For example, we are doing this with the Genoviz DAS2 server to provide
> auto-load hints to IGB to indicate whether all features of a particular data
> type should be loaded for a given genomic sequence (chromosome) or if it
> should be loaded on-demand.
>

Do you have a small example of how this works?  I can see how this kind of
information is useful, but it's not obvious to me how you can encode it as
XSL rather than something DAS-specific?


> Do any of the DAS 1.5/1.6-based servers and clients do something like this?
>

At one point, the old biojava DAS client code (which was used in an early
demonstration heavy-client DAS application, but may have bit-rotted by now)
would use the feature-counts in the 'types' response to estimate feature
density, and => sensible sizes of tiles to use when fetching features.  I
seem to remember that this worked fairly well against some servers, but was
a bit tempremental because:

           1) the feature counts are optional.

           2) Even when they are implemented, some servers (at the time,
anyway) could be pretty slow about returning them.

...so it's not a silver bullet.  I could certainly imagine some kind of
"density hint" attribute in a stylesheet being helpful.

               Thomas.