The Sensor Observation Service (SOS) extension for ArcGIS Server is implemented as a so-called Server Object Extension (SOE). It allows querying of observations, procedures/sensors, as well as features observed by sensors. The interface is compliant with the SOS 2.0 standard from OGC.
<om:name xlink:href=""http://dd.eionet.europa.eu/vocabulary/aq/processParameter/AT""/>
<om:value>The daily average or daily mean is the average of all valid hourly values for a day. A daily or 24-hourly average is calculated if at least 18 valid hourly values are available.</om:value>
should be changed to: