A spatial mapper links an Entity to a Spatial Engine. This linkage is not required and in fact, may not be possible if there is no spatial information associated with the entity.
If there is spatial information that relates to the entity and you want the users to be able to perform spatial operations (select by polygon, etc.) on the entity then a link should be set up.
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The spatial mapping also specified which column in the underlying table is used to uniquely identify an entity, this is set with the key attribute.
Because the key used by Weave to identify an entity may be different from that used by the underlying spatial entity to identify a feature there has to be a mapping performed between the Weave keys and the spatial engine feature ids.
Generally, this mapping is performed once at system startup and doesn't change unless Weave notices a change in the count of the available rows in the underlying table (which is checked every five minutes). This is assuming that the underlying keys/feature ids don't change and only the addition/removal of a row in the table would have an effect on the key mapping.
However there may be times when this is not suitable, for example, if the table if very large it can take a long time to read all of the key mappings and they can take up a large amount of memory, or if the key mappings do actually change frequently, so this initial key mapping can be disabled and the mapping between the Weave keys and the spatial engine feature ids can be performed on-the-fly each time Weave needs to transform a key to a feature id, or a feature id to a key. Obviously, this will have an impact on performance, since it requires a trip to the spatial engine for each transform, rather than having it done once and the transform performed in memory.
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urn:com.cohga.server.spatial.mapper#1.0
Tags
mapper
Properties
Name | Type | Required | Description |
id | string | yes | unique identifier |
spatialEngine |
yes | The identifier of the spatial engine that the mappings |
should link to | |||
crs | string | no | The CRS to override for entities that don't provide an explicit value |
filter | string | no | Provide a CQL formatted filter to apply when performing spatial operations with this mapper |
dynamic | boolean | no | Should the key/fid transform be performed on each lookup |
cache | boolean | no | Should dynamically looked up key/fid transforms be cached in memory |
Sub-tags
Name | Type | Cardinality | Description |
mapping | urn:com.cohga.server.spatial.mapper#1.0:mapping | 1..n | A collection of mappings that link entities to spatial items |
Content
None
Notes
- The CRS property does not perform any transform, it just tells the server how the actual data is stored in cases where the underlying spatial engine does not supply this information or supplied an incorrect value.
mapping
Properties
Name | Type | Required | Description |
entity | yes | The identifier of the entity |
spatialEngine
no
that this mapping applies to | |||
table | string | yes | The name of the spatial item within the spatial engine that this mapping applies to |
key | string | no | The attribute of the spatial item that uniquely identifies an entity |
crs | string | no | Provide a Coordinate Reference System if the underlying spatial engine doesn't provide the correct information |
filter | string | no | Provide a CQL formatted filter to apply when performing spatial operations with this mapping |
dynamic | boolean | no | Should the key/fid transform be performed on each lookup |
cache | boolean | no | Should dynamically looked up key/fid transforms be cached in memory |
| unique | boolean | no | Tells Weave that the key values will be unique, so that it doesn't have to check for itself. Weave can optimise the handling of spatial selections if the keys are unique, if you know the keys are unique you can set this to true and Weave will not need to pre-check for itself. |
Sub-tags
Name | Type | Cardinality | Description |
mapping | urn:com.cohga.server.spatial.mapper#1.0:mapping | 0..n | If more that one underlying feature maps to the entity then multiple sub-mapping tags can be used to specify additional mappings |
Content
None
Notes
- The CRS property does not perform any transformation, it just tells the server how the actual data is stored in cases where the underlying spatial engine does not supply this information or supplied an incorrect value.
- Only 1 level of nesting is supported for sub-mappings.
- Only spatialEngine, table and key are allowed in sub-mapping tags.
- Only table is required, spatialEngine and key and be infered key can be inferred from the parent mapping.
Examples
| Code Block | ||||||||
|---|---|---|---|---|---|---|---|---|
| ||||||||
<mapper:mapper id="mapper.mainarcsde"> <spatialEngine>spatialengine.arcsde</spatialEngine> <mapping> <entity>property</entity> <table>PROPERTY</table> <key>PID</key> </mapping> <mapping> <entity>roads</entity> <key>RD_NAME</key> <mapping> <table>MAJOR_ROADS</table> </mapping> <mapping> <table>MINOR_ROADS</table> </mapping> </mapping> <mapping> <entity>suburbs</entity> <table>SUBURBS</table> <key>LOC_NAME</key> </mapping> <mapping> <entity>council_buildings</entity> <table>BUILDINGS</table> </mapping> </mapping> <mapper:mapper id="mapper.oracle"> <spatialEngine>spatialengine.oracle</spatialEngine> <mapping> <entity>drainage</entity> <spatialEngine>spatialengine.oracle</spatialEngine> <table>DRAINAGE</table> </mapping> </mapper:mapper> |
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