Thanks Bryce, comments and clarifications inline.
Bryce L Nordgren wrote: > Source: > http://docs.codehaus.org/pages/viewpage.action?pageId=62876 > > I don't know anything about goals 1 & 2. > > These relate to discussions already underway about handling new types. > Goal 3 seems appropriately positioned. > > Prologue to the rest: > "Features" and "Coverages" ala ISO do not seem to correspond to that which > is served by a Web Feature Service / Web Coverage Service. Yes - this is true. Its a function of a parochial approach to WCS. WCS also has a historic arbitrary refusal to inherit from emerging ideas of an OWS_common at the time. One reasone to say if we want to do arbitrary coverages, we'd be better off starting with WFS and treat WCS as a "convenience API" for 2D raster grids. > In particular, > WCS/WFS divide the problem into the Raster/Vector problem spaces, and ISO > divides the problem into single-valued/multi-valued problem spaces. A WFS, > serving a particular feature, performs many of the functions which belong > to a DiscreteCoverage in the ISO world. Feature collections may not represent a coverage - there is no requirement for a mapping from a domain to a range, but this may be splitting hairs in practice. > (e.g., spatially indexed lookup of > values from a collection of range/value pairs, where the values are > homogeneous within the collection; range=defaultGeometry; value=everything > else). I remain blissfully ignorant of ISO's efforts to adopt WFS into > their framework (19141, I think). > > Short version: if I was pressed to describe what an WFS is, I'd have to say > it is a discrete coverage implementation using Web Services technology. A > WCS would then be an implementation of DiscreteGridPointCoverage > implementation. Messy, because this implies a parent-child relationship > between WFS & WCS. > WCS could also be seen as implementing a ContinuousQuadrilateralGridCoverage, but not exposing the interpolation function ? > Goal 4: > Not sure I understand what is the main point. Why limit ourselves to POJO > databases? Conversely, if we can create featuretypes from inspection of an > arbitrary JDBC data source now, why does this not carry over to POJO > databases? Why do POJO databases require an extra abstraction layer > instead of just a driver? I'm not sure I "get it" enough to ask anything > intelligent. > OK - there are two kinda non-obvious reasons for this - one is that its a separate set of business goals that shares the need for operations etc, but also because we I hope can make POJOs to implement coverage operations and inject them using this mechanism, allowing us to extend the types of coverages supported. > Goal 5: > Unsure as to the proposal. Is this an addition to a WFS which basically > allows the server to "cascade" to a WCS? Are we trying to wrap the bare > bones raster data with GML representative of a Feature possessing the > characteristics of a 19123 Coverage? yes > Should we also consider repackaging > the whole shootin' match into GML: each returned pixel/grid cell gets its > own record in the returned GML (or shapefile)? In ISO speak, someone might > want to treat DiscreteGridPointCoverage data as if it were a plain > DiscreteCoverage. > we might want to, but at the moment I have seen no strong drivers for this. But we do want to shift the rest of the metadata about coverages through processing chains. > Goal 6: > This is the Holy Grail! I know exactly whazzup with this one! For some > thoughts on how vertical/temporal subsetting may be handled, see the > analysis of WMS 1.3.0 on the Multidimensional WCS page. They've provided > for this functionality. ( > http://docs.codehaus.org/display/GEOS/Multidimensional+WCS) Perhaps future > versions of WMS/WFS will adopt the same strategy? I'm not sure you're > going to be able to use a WFS to query a WCS based on the grid cell values > unless you adopt a cascading mentality. The WFS is going to have to hide > the WCS entirely, and can't just include a link so the user can get the > data directly. > I think I agree - WCS 1.0 can be used only for subsetting a small subclass of coverage types we might enable. Maybe a WCS 2.0+ will be more flexible one day. > One minor point: if it's served by a WCS, it's a discrete grid point > coverage. No continuous coverages are served over the net. > But we want to free ourselves of this very arbitrary limitation. Without having to redefine WCS, by using WFS which is perfectly capable, if we can invoke operations. > Bryce > ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
