Home' Position : Position Oct Nov 2015 Contents standard defines the rules for requesting
and communicating this structured data.
Standards are often built in layers,
one on top of another. The OGC and ISO
Geography Markup Language (GML) is
built on top of the eXtensible Markup
Language (XML). GML is an XML
grammar to define geographic features.
GML serves as a modelling language
for geographic systems as well as an
open interchange format for geographic
transactions on the Internet. GML is
based on a number of abstract models
that are captured in a variety of ISO
standards, such as 19107 and 19111.
Many proprietary and open source
geomatics software products implement
GML, an open standard, so that those
products can communicate via the web
with other software, whether proprietary
or open source.
does all spatial data of a
particular kind need to be
stored in a single format?
No! That's the beauty of open encodings
and interfaces. No batch file conversion
of data is necessary. Different software
vendors will continue to have different
ways of storing data, different formats,
and different algorithms for processing
data, but that is not a problem. Any
software product that implements an
open interface standard can convert data
on the fly between data encoded using
the open encoding and data encoded
using the software's internal format. To
implement an open interface, a developer
writes code that maps from the internal
storage model to the model defined in
the standard encoding. This is not always
a trivial task, but the developer doesn't
need to change the internal storage
model. The interface is an 'add-on' to
Until fairly recently, most open data was
provided as downloadable data files, whose
openness derived from adherence to a
particular open format. This is still the case
for much open data, but in many situations,
Web services provide a better alternative,
as described in the next paragraph.
Why are open standards
important for open
First, consider that what we have been
calling 'software' in the paragraphs above
is now more commonly referred to as
'services'. Some vendors were providing
service architecture as early as the late
1980's, but 'software as a service' has
now become the dominant computing
paradigm. Software residing on remote
servers is now accessible via the internet
as a service, for use by client software
residing on countless different kinds
of devices -- some mobile, some on our
desktops, some embedded in 'things'. If the
remote servers implement open interfaces,
those services are available to any client, if
the client has permission and if the client
implements the same interface standard.
Many simple services, such as using a
bounding box to select a geographic region,
are now routinely performed by anyone
using a Web services-based map browser.
Previously, this operation required locally
installed software and data.
Much of the Web is not open, because
internet platform vendors seek to bring
their customers into proprietary software
platforms and ecosystems. But most open
data advocates would not want to lock
their data into those proprietary silos.
Open interface and encoding standards
enable open data providers to fulfil
their vision of openness, unrestricted by
Cost reduction is a major-long
term benefit of using open standards.
Because many geoprocessing software
vendors already implement OGC and
ISO/TC 211 standards, additional
interface development is minimised.
Buyers solution providers can choose
software vendors based on best fit and
best of breed. Different software and
service packages can be used together
as interoperating solution components.
For governments, open data is
simply a continuation of spatial data
infrastructures (SDI). The proliferation
of mobile devices and Internet of Things
devices creates new demand for SDI.
Bus schedule data, for example, can be
made accessible to app developers, so
they can use that data in applications.
A shopping centre might want a kiosk,
showing timely, up-to-the-minute
information about when the next bus
will arrive and where it will go after
stopping. A paper bus schedule can't
provide real-time data. A kiosk is
more convenient for passengers than
going to the bus company's website.
There are countless examples like
this that illustrate the value of Web
service based open data. Open data
breeds innovation that can improve the
information environment for citizens,
city departments and businesses.
Figure 2. Many
implement open data
policies and provide
open data portals.
Cities are beginning
to do the same.
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