Hello,
There is a quite important difference between implement and compliant.
Anyone (any OGC member) can claim to implement a standard, by just
reading the specification and code it. You can only claim to be
compliant if you successfully passed the OGC CITE Test Suite for the
standard you've implemented.
Regards,
Frédéric
On 05/04/2013 15:34, Martin Desruisseaux wrote:
Hello Amila
Le 05/04/13 12:57, AMILA RANATUNGA a écrit :
the slide 21 describes remaining code to move as WMS, WCS, WCTS, WPS and
more. Is that mean Apache SIS does not support them?
Yes. SIS is still in an early stage and does not support WMS, WCS and
similar services yet.
And GeoTk code was moved to SIS and claims that reference
implementation of
GEOAPI.
Geotk code is in process of being moved to SIS. But only metadata port
is close to completion. The next module to port will be referencing
(hopefully completed before FOSS4G in September).
geotoolkit.org (...snip...) Mapfaces (...snip...) constellation-sdi
(...snip...) puzzle-gis (...snip...)
Will integrating those into sis make one step ahead to "SIS
well-suited to
some communities (*scientists, but also non-scientists* wanting to
explore
data in more dimensions than the usual x,y)."?
Maybe I should said that those projects will not be automatically
added to SIS. They will be offered, but by the time we reach them, the
technologies may have evolved to a point where peoples may want to
explore other approaches. For example MapFaces is built on top of JSF.
But maybe some peoples will want to explore the Play framework
instead. An other example is Swing-based technologies, which are going
to be phased out in favour of JavaFX. However we may still use the
existing code as a starting point and try to port them to the new
technologies. We will revisit this issue when we will be there.
The core part aiming to make SIS "well suited to scientists" is Geotk.
First by its focus on ISO 19115 metadata for describing the data.
Those metadata include a package for describing data quality, an
aspect usually neglected by mass-market projects but important for
scientists. The GeoTk (future SIS) referencing module takes its
information directly from the EPSG database, which provides us
information about transformation accuracy and CRS (Coordinate
Reference System) area of validity. Many popular projects use
simplified version of EPSG database without those information, since
not anyone see them as useful. GeoTk paid high attention to
correctness through our current effort of expanding
'geoapi-conformance' test suite with the GIGS tests (provided by the
EPSG authors). GeoTk also have support for n-dimensional CRS. Those
CRS may be more than (x,y,z,t), for example meteorologists use 2 time
axes and oceanographers often use pressure instead of z. On the
coverages (rasters) side, GeoTk provides a way to describe the meaning
of pixel values (by contrast with some projects handling rasters
basically as RGB images), which allow for example to compute "gradient
of sea surface temperature" without confusing a temperature value with
a pixel covered by a cloud (without such knowledge, calculations like
"gradient" produce strong artefacts). Large dataset can be organized
in a database schema designed for making easier the statistical
analysis over time series.
Constellation-SDI simply uses the "building blocks" provided by
SIS/GeoTk for providing web services. Our approach for aiming such web
services as "well suited to scientists" is to make sure that we use
properly the tools provided by SIS. Similar reasoning apply to
Puzzle-GIS. Providing those web services and desktop application
directly in SIS would allow SIS to run "out of the box", but community
may decide that this is not a goal.
We also referred the white paper[2].There are OGC compliance products
and
OGC implementing products[3]. What is the main difference? For an
example
zoo project is considered as OGC implementing. But the site says " It
provides an OGC WPS compliant developer-friendly framework to create and
chain WPS Web services".
I suspect that "OGC compliant products" and "OGC implementing
products" can be understood as synonymous. However Frédéric Houbie
would known better.
As Jun mentioned Osgeo live dvd has many products [4]. If they are
compliance with OGC. implementing OGC standards with Airavata will make
such products inter-operable with Airavta. But those have implemented
specific OGC standards (As Martin said " I think that OGC standards
are so
large that no single software in the world implement all of them").
So for
such a project what will be the major consideration should be. Or how
far
an integration SIS with Airavata will solve this problem?
The Web Map Services (WMS) is probably the most widely implemented OGC
standard. Having SIS to implement WMS, WMTS, WCS and WFS is a must.
Those 4 standards will probably allow inter-operability with the vast
majority of OGC-compliant products.
Next, there is other standards not as-widely known but nevertheless of
interest for us. For example Web Processing Services (WPS) for
launching calculations on distant machines. SensorML for expressing
sensor data (e.g. monitoring environmental parameters). There is an
ungoing "uncertainties" working group at OGC which may be seen as a
specialized work for geoscientists. There is also other groups like
"hydrology", "aviation" and "law enforcement" for policemen. "Law
enforcement" is an example of OGC work which will probably not by my
personal priority. This illustrates the idea that a single project may
not implement every OGC standards.
Next, there is what OGC calls "best practice" for specific domains.
For example the OGC Met-Ocean working group has emitted
recommendations about the way to use WMS with meteorological and
oceanographical time series. This is because meteorologist have
specialized needs for example in the way to handle time, not
considered of common interest enough for being part of the base WMS
standard. Those recommendations are a kind of gray area, not official
standards but nevertheless something we should comply to if we want to
increase the chances to be inter-operable with Meteo-France or the UK
MetOffice.
Martin
