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param

The param attribute specifies a subset of a data source or resource file to be used as data for a map or graph element. The value of the param attribute depends upon the context in which it is used. See the notes below for details.

Supporting Tags

The param attribute is supported by the <data> tag. Its usage depends on the parent of the <data> tag, so it may be required, optional, or not applicable in certain cases. See the notes below for details.

Examples

<contour>
  <data src="latest.mdf" param="TAIR"/>
</contour>
         
<observation>
  <data network="Oklahoma Mesonet" param="NAME"/>
</observation>
         
<overlay>
  <data src="Oklahoma Maps" param="County borders"/>
</overlay>
         
<overlay>
  <data param="State border"/>
</overlay

Notes

In many cases, the param attribute represents a measured or derived parameter from an observation network, and its value consists of a short descriptor that uniquely identifies the parameter. Traditionally, parameter descriptors are four characters in length. However, they may be longer in some cases. Examples of this usage include <data> tags within a <contour> or <vector>. Parameter descriptors for the observation networks currently supported in WxML are defined in the OCS Resources section.

In other cases, the param attribute represents a resource within a file, and its value consists of the name of the resource. Examples of this usage include <data> tags within an <overlay>. Overlay resources currently supported in WxML are defined in the OCS Resources section.

Sometimes, the <data> tag may not require a param attribute at all. Examples of this include <data> tags within a <site>.

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