2.2.1   MapFile Metadata

The following mapfile metadata are used by MapServer to handle map context information:

(Note that some parameters have width, height, format, and href, and some only have format and href. This is because width and height are only used for images and parameters that do not have them are text or html. For consistency with the spec MapServer supports height and width for all parameters, but they should only be used for images)

2.2.2   Sample Map Context Mapfile

NAME WMS_CONTEXT
STATUS ON
SIZE 400 300
SYMBOLSET ../etc/symbols.sym
EXTENT -2200000 -712631 3072800 3840000
UNITS METERS
SHAPEPATH "../data"
IMAGECOLOR 255 255 255
FONTSET ../etc/fonts.txt

WEB
  IMAGEPATH "/ms4w/tmp/ms_tmp/" 
  IMAGEURL "/ms_tmp/"
  METADATA
    "wms_abstract" "Demo for map context document. Blah blah..."
    "wms_title" "Map Context demo"   #### REQUIRED
  END
END

PROJECTION
  "init=epsg:42304"
END

LAYER
  NAME "prov_bound"
  TYPE RASTER
  STATUS ON
  CONNECTION "http://www2.dmsolutions.ca/cgi-bin/mswms_gmap?"
  CONNECTIONTYPE WMS
  METADATA
    "wms_name"            "prov_bound"
    "wms_server_version"  "1.1.1"
    "wms_format"          "image/gif"
    "wms_srs"             "EPSG:42304"   
    "wms_title"           "Canadian boundaries"  #### REQUIRED
    "wms_onlineresource"  "http://www2.dmsolutions.ca/cgi-bin/mswms_gmap?"  #### REQUIRED
    "wms_dimensionlist"             "time,width"    
    "wms_dimension"                 "time"
    "wms_dimension_time_unitsymbol" "t"    
    "wms_dimension_time_units"      "ISO8601"
    "wms_dimension_time_uservalue"  "1310"
    "wms_dimension_time_default"    "1310"     
    "wms_dimension_time_multiplevalues"  "1310,1410" 
    "wms_dimension_time_nearestvalue"  "0"        
  END
END  

LAYER
  NAME popplace
  TYPE RASTER
  STATUS ON
  CONNECTIONTYPE WMS
  CONNECTION "http://www2.dmsolutions.ca/cgi-bin/mswms_gmap?"
  METADATA
    "wms_name"              "popplace"
    "wms_server_version"    "1.1.1"
    "wms_format"            "image/png"
    "wms_srs"               "EPSG:42304"
    "wms_title"             "Canadian Cities" #### REQUIRED
    "wms_onlineresource"    "http://www2.dmsolutions.ca/cgi-bin/mswms_gmap?" #### REQUIRED    
  END
END # Layer

END # Map File

2.5.1   Support for Local Map Context Files

There is a new cgi parameter called CONTEXT that is used to specify a local context file. The user can then use MapServer to request a map using the following syntax:

http://localhost/mapserver.cgi?MODE=map&MAP=/path/to/mapfile.map&CONTEXT=
                     /path/to/contextfile.xml&LAYERS=layer_name1 layers_name2           

Note that all layers created from a context file have their status set to ON. To be able to display layers, the user needs to add the LAYERS argument in the URL.

2.5.2   Support for Context Files Accessed Through a URL

The syntax of using a web accessible context file would be similar to accessing a local context file:

http://localhost/mapserver.cgi?MODE=map&MAP=/path/to/mapfile.map&CONTEXT=
            http://URL/path/to/contextfile.xml&LAYERS=layers_name1 layer_name2     

Due to security concerns loading a file from a URL is disabled by default. To enable this functionality, the user needs to set a CONFIG parameter called CGI_CONTEXT_URL in the default mapfile that will allow this functionality. Here is an example of a map file with the CONFIG parameter:

# Start of map file
NAME map-context
STATUS ON
SIZE 400 300
EXTENT -2200000 -712631 3072800 3840000
UNITS METERS
IMAGECOLOR 255 255 255
IMAGETYPE png
CONFIG "CGI_CONTEXT_URL" "1"
...
WEB
  ...
END
LAYER
  ...
END 

END

2.5.3   Default Mapfile

To smoothly run a MapServer CGI application with a Map Context, the application administrator needs to provide a default mapfile with at least the basic required parameters that will be used with the Context file. This default mapfile can contain as little information as the imagepath and imageurl or contain a list of layers. Information coming from the context (e.g.: layers, width, height, ...) would either be appended or will replace values found in the mapfile.

Here is an example of a default map file containing the minimum required parameters:

NAME CGI-CONTEXT-DEMO
STATUS ON
SIZE 400 300
EXTENT -2200000 -712631 3072800 3840000
UNITS METERS
IMAGECOLOR 255 255 255
IMAGETYPE png
#
# Start of web interface definition
#
WEB
  MINSCALE 2000000
  MAXSCALE 50000000
#
# On Windows systems, /tmp and /tmp/ms_tmp/ should be created at the root 
# of the drive where the .MAP file resides.
#
  IMAGEPATH "/ms4w/tmp/ms_tmp/" 
  IMAGEURL "/ms_tmp/"
END
END # Map File