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Sono in ... Forum arrow News arrow Standard arrow WFS Schema Mapping
WFS Schema Mapping PDF Stampa E-mail
lunedì 07 luglio 2008

In questo recente post, Ron Lake (uno dei papà del GML) evidenzia la necessità di definire degli schemi WFS pubblici, secondo cui interscambiare dati:
 

WFS Schema

Un ente potrebbe continuare ad usare un proprio schema interno e limitarsi ad esporre un servizio WFS conforme allo schema pubblico per risolvere problemi di nomenclatura, oppure di rappresentazione geometrica dei dati:

One approach (I will talk about this more in a subsequent blog) is to create a public schema that represents the feature types of interest for all of the prospective users. We might for example have a common model for roads, buildings and land parcels that spans all the counties of a state, municipalities of a province or country.  This common model is expressed in terms of a schema (e.g. GML Application Schema) that states the names of the feature types, and the names, types and multiplicities of their properties. For example our schema might define the feature types (road, river, bridge, building), and for a road it might specify the properties name, description, numberOfLanes, surfaceType, and centerline. The road might have any number of names, a single description, a single numberOfLanes (integer), a single surfaceType (enumeration) and a single centerline (LineString).

Now, it is unlikely that we will get all of the counties, municipalities, states, etc. among whom we are trying to share data to adopt this common schema. They will all have existing use cases for their data, and they will have already developed schemas that model roads, buildings, and land parcels in order to support those use cases.  They will not be willing, nor able, to change their schema to comply with the public one.  This is where schema mapping comes in.

The purpose of a WFS is to provide, in part, vendor neutral access to geospatial data, but more importantly to be able to provide this data relative to an external public schema.  This means that the client of the WFS sees a schema (obtained via a DescribeFeature request) that is the public schema and is unaware of the schema used by the underlying and (to her/him) opaque data store.  Note that this requirement exists even if all of the nodes in the network (for sharing or aggregation) were using the same vendor software.


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  Commenti (2)
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Scritto da Andrea P., il 08-07-2008 00:09
Complimenti per la segnalazione, l'articolo e' molto interessante.
Scritto da Piergiorgio Cipriano, il 08-07-2008 17:57
C'è un altro post interessante di Ron Lake, pubblicato ieri sul tema del "Cascading WFS": 
http://www.galdosinc.com/archives/530 
 
pg

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