Re: [Geoserver-users] App Schema Transactions

Fri, 07 Jan 2011 04:31:32 -0800

Hi Chris,

Do you know if the parsing of complex GML features made it back into the trunk?

Regards,

Andy


On 16/12/2010 15:42, Chris Holmes wrote:
Note there are some developers who have built support for parsing complex GML features.  They just haven't got the go ahead and time to contribute the code back.  Though I'm meeting them today, so will mention that there is real community interest.

On Mon, Dec 13, 2010 at 9:08 PM, Ben Caradoc-Davies <[email protected]> wrote:
Andrew,

there are technical barriers, such as the lack of support for parsing
complex GML features. WFS-T would require parsing complex features
before they could be inserted into a database. app-schema is build on
simple features, and so locking would have to be coordinated with these.
Furthermore, feature chaining would mean that related features would
also have to be locked.

The biggest technical problem in my view is that CQL expressions are
used to implement polymorphism (conditionals) and to construct data in
the middleware. CQL expressions are in general irreversible. This is a
huge problem in using the existing mapping as it stands. So perhaps a
new mapping might be required? (Or a new ORM backend that addresses both
reversibility and efficiency in one go?)

One conceptual hurdle is object identity and referential integrity. When
you update a complex feature, are you also updating nested properties,
or just the top-level feature? What about properties that are shared
between multiple features (associations)? What about multivalued
attributes: do you need to garbage collect to preserve foreign key
constraints?

Sorry, I have more questions than answers. This is an interesting
problem.  :-)

Kind regards,
Ben.

On 13/12/10 20:02, Andrew Chamberlain wrote:
> Hi All,
>
> We were just sizing up the task of enabling transactions with the
> app-schema plugin, and were wondering if anyone knew of any major issues
> which might prevent / trouble the development of this?  Questions which
> immediately come to mind are:
>
> 1) Would the current mappings be re-usable, or would a separate set be
> needed for the reverse (i.e. write) direction?
> 2) Would such a reverse mapping be possible with the current mechanisms?
>
> I'm hoping that the original reason that transactions wasn't implemented
> was simply a matter of limited time and funds, and not something technical.
>
> Any thoughts/pointers would be much appreciated.
>
> Best regards,
>
> Andy
>
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--
Ben Caradoc-Davies <[email protected]>
Software Engineering Team Leader
CSIRO Earth Science and Resource Engineering
Australian Resources Research Centre

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