onsdag den 26. marts 2008

ESRI Dev Summit 2008 - The real skinny



The REST API does not support curves to be returned.
When curves are encountered, they are densified automatically and returned as polylines.
Support for curves is being planned for in the future versions.

They were also open to the idea of GeoJSON converters in the JavaScript API for the future.
The shapes returned by the REST API are not GeoJSON compliant. But the ESRI developers seem open to support GeoJSON when it is finally ratified by the standards committee.
The REST API does all its work by using the ArcGIS Server SOAP API. See the notes below for the reasons why.

JavaScript API

The ESRI developers chose to use the DOJO toolkit primarily because its graphics capabilities.
The DOJO client-side libraries provide support for performing some simple spatial operations like ‘intersection’ on the client-side.

The intellisense for the Javascript API currently has some problems in Visual Studio 2008.
The client-side layers provides support for attributes on the client-side features. Attributes on client-side features are not even supported in VE and Google Maps.
The client-side layers support events.

Currently, only one client-side layer is supported. The reason for this being (according to the ESRI developers) there are problems with listening to events on features that are not on the top-most layer. ESRI is currently researching the problem and is trying to find ways to make multiple client-side layers work.

The client-side JavaScript for the .NET ADF has been completely re-built in 9.3.
Changes are already planned for the JavaScript API between the Beta version and the final release.

An object model diagram for the JavaScript API might also be available.

Map cache

ArcGIS Server 9.3 supports the following tiling scheme
VirtualEarth (256X256)
Google Maps (256X256)
ArcGIS Online (512X512)


The Map cache generated using the VirtualEarth tiling scheme does not generate tiles using the quadkey naming scheme for the file names generated but only the tiling scheme is the scheme.
The REST API has built-in support for handling quadkey naming scheme, it maps the quadkeys to the file names generated by the ArcGIS Server cache.

The WMS Service of the MapServer object will start taking advantage of the Map cache if available starting in 9.3.


Sounds like SDE will support storing shapes in SQL Server 2008 as SQL CLR types also. This should enable other applications to access and use spatial data in the SDE without ArcObjects.

Note: It was decided to use SOAP over DCOM for the REST handlers to talk to ArcGIS Server because ESRI realized after running some metrics that SOAP was more performant than DCOM to access ArcGIS Server functionalities. The chatty nature of DCOM reduces its performance over SOAP. When using DCOM, the client uses a proxy to communicate with the server object.

That means every time the client accesses a property on the server object, it is accessed over the network. But when using SOAP, an object representation is completely serialized and sent to the client so that property access doesn’t need to be over the network.

Even though it is not completely documented, it is possible to access Server Object Extensions over SOAP directly with some custom programming.

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