[Mapserver-dev] Re: time support

Steve Lime steve.lime at dnr.state.mn.us
Wed Dec 17 00:21:30 EST 2003

A timeindex would not be a shapefile, rather simply a temporal lookup
table. An xbase file would do nicely. I'll have to think about just
extending a TILEINDEX. that may be pushing things too far, but it may
not. You'd probably want a seperate TILEFILTER and TILEFILTERITEM
though. The timeindex itself would contain a few extra metadata fields.
One would be a "band" column so that a single image where each band
represents a different date or date range could be queried temporally.
Either way I agree that filtering on time is desireable. I think I could
write regular expressions in the lexer to identify at least a subset of
extended date/time formats as defined in ISO8601, more if a date
delimiter was used. From there it would be easy to add date comparisons
IF a ISO8601 compliant library already exists, I'll start looking. That
way date expressions could be used with any data source if a column
contained ISO8601 formated date/time strings. In that case using a
timeindex for anything but raster data may not be necessary. Raster data
is certainly the task at hand for me.


>>> Daniel Morissette <morissette at dmsolutions.ca> 12/16/03 5:25 PM >>>
(I decided to move this to mapserver-dev)

Steve Lime wrote:
> Do you mean TILEINDEX or the new TIMEINDEX? I could certainly see
> filtering on the TIMEINDEX, especially as applied to non-raster data.
> Using filters on tiles could certainly be done but would there be any
> real practical use for the output. The new TIMEINDEX is accomanied by
> TIMEID, and the TIMEID could be interpreted as a MapServer expression
> you could process mutiple files at one time. 

I didn't know about the name of the new TIMEINDEX so I really meant 

My idea was simply that instead of creating a new TIMEINDEX we could 
simply extend the existing TILEINDEX to support filter expressions. The 
expression could be based on time or on any other attribute in the 
tileindex file.

We would also need to extend the expressions stuff in MapServer to 
support time comparisons and time ranges. That would be a generic 
enhancement to the expression stuff and could be class EXPRESSIONs and 
not just in the layer FILTER.

Does it make more sense? I'm scared I'm not expressing myself very

> That would be more work to
> add than simply interpreting TIMEID as a single value.

I actually thought that extending the TILEINDEX to support FILTER would 
be simpler.  Would it not just be a matter of adding a call to 
msEvalExpression() in the code that scans the tile index?

  Daniel Morissette               morissette at dmsolutions.ca
  DM Solutions Group              http://www.dmsolutions.ca/

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