Pitney Bowes MapInfo Professional - Manual (Page 415)

The WFS client supports GML2 (OGC GML V2.1.1). The OGS WFS Specification states that all servers
should support GML2, but may also support other formats. The server provides information on the formats
available, and the client makes the request for the data in the format it can use. If the server does not
support GML2, it will not be supported by the MapInfo WFS client.
GML2 does not contain any style information. You can provide style information to associate with a
particular WFS table.
A WFS request contains a description of query operations that can be applied to one or more features.
The client generates the request and posts it to a WFS using HTTP. The web feature server then reads
and executes the request.
The GetCapabilities operation queries the WFS server for capabilities. Then the MapInfo Professional
WFS client can generate a query appropriate for the WFS server and table.
Each table in the WFS server can result in a single MapInfo table. The mapping is always 1-to-1 (unlike
WMS, which is many-to-1).
The TAB file retrieved from a WFS server resembles a read-only DBMS linked table. It contains a MAP
file and a DAT file, and acts like a read-only native table. Information is stored so that the table can be
refreshed from the WFS server.
The sequence of actions can be summarized as follows:
1. After sending a GetCapabilities request to a WFS server, the server returns a list of WFS layers
(FeatureTypes) that it can provide.
2. The user picks a WFS layer to fetch from the server, MapInfo Professional then sends a
DescribeFeatureType request to the server. This response is an XML schema that describes the
feature.
3. The user can then select which columns and/or rows to fetch.
4. MapInfo Professional sends a GetFeature request to the WFS. If the user did not select a subset of
columns, all columns will be requested by default.
5. The response is a GML document containing the feature collection. Each feature represents one
"record" in the MapInfo table.
There is a list of WFS servers in the client to help you get started in using this functionality.
Since the data you retrieve using the WFS is remote, it may change from time to time. You can
refetch your WFS data manually using the refresh process. See Refreshing your WFS Data in
the Help System for more information. Note:
WFS Server Requirements
You must have a working Internet connection whenever you retrieve WFS data. To display GML2 data
correctly in the MapInfo Professional Web Feature Service, the server you are requesting information
from must:
• Support versions 1.0.0 and 1.1.0 of WFS. The MapInfo Professional WFS client sends the initial
GetCapabilities and specifies version 1.1.0 (unless version 1.0.0 is set in MapInfo Professional as a
preference). If the server you are requesting information from does not support 1.1.0 (or 1.0.0), MapInfo
Professional cannot use that server and no further operations are allowed.
• Respond to GetCapabilities request using Http GET in XML.
• Respond to the GetFeature request by returning GML2 (OGC GML 2.1.1). The server's
GetCapabilities response should include this information. If the server does not claim to use GML2 as
the Result Format for GetFeature, then MapInfo Professional cannot use the server and no further
operations will be allowed.
• Conform to the OGC GetCapabilities schema. If the server GetCapabilities response does not
conform to the schema, MapInfo Professional may not be able to read portions of it. This may mean
that MapInfo Professional misses items that the server is trying to communicate, such as feature types
(tables), or filters. In some cases, MapInfo Professional will not be able to deal with the server, since
415 MapInfo Professional User Guide
Chapter 16: Working with Data from a Web Service