OGC 08-094r1 SWE Common Data Model
block-separator-chars = Value of the blockSeparator attribute token-separator = [white-space] token-separator-chars [white-space]
block-separator = [white-space] block-separator-chars [white-space]
White spaces around separators are in fact only allowed when the “collapseWhiteSpaces” attribute is set to ‘true’ which is the default.
9.2.2 Rules for Scalar Components
The value for a scalar component is encoded as its text representation, following XML schema datatypes conventions.
scalar-value = xs:bool xs:string xs:double xs:int xs:date xs:dateTime
Nil values are included in the stream just like normal scalar values. Since their data type has to match the field data type, there is no special treatment necessary for a decoder or
encoder. It is the responsibility of the application to match the data value against the list of registered nil values for a given field in order to detect if it is associated to a nil reason
or if it is an actual measurement value.
9.2.3 Rules for Range Components
Range components are encoded as a sequence of two tokens each one representing a scalar value separated by a token separator:
min-value = scalar-value max-value = scalar-value
range-values = min-value token-separator max-value
9.2.4 Rules for DataRecord and Vector
Values of fields of a “DataRecord” are recursively encoded following rules associated to the type of component used for the field’s description i.e. scalar, record, array, etc. and
separated by token separators as expressed by the following grammar:
field-count = Number of fields in the record minus one. Greater or equal to 0 any-field-value = scalar-value range-values record-values choice-values array-values
mandatory-field-value = any-field-value optional-field-value = “Y” token-separator any-field-value “N”
field-value = mandatory-field-value optional-field-value record-values = field-value field-counttoken-separator field-value
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SWE Common Data Model OGC 08-094r1
When a field is marked as optional in the definition, the token ‘Y’ or ‘N’ shall be inserted in the data block. When the field value is omitted, the token ‘N’ is inserted alone. When it
is included, the token ‘Y’ is inserted followed by the actual field value.
Requirement
http:www.opengis.netspecSWE2.0reqtext-encoding-rulesoptional-field-marker-present
Req 92. The ‘Y’ or ‘N’ token shall be inserted in a text encoded data block for all
fields that have the “optional” attribute set to ‘true’.
Coordinate values of “Vector” components are encoded with a similar syntax, but a coordinate value can only be scalar and cannot be omitted:
coord-count = Number of coordinates in the vector minus one. Greater or equal to 0 vector-values = scalar-value coord-counttoken-separator scalar-value
The following example shows how elements of an array defined as a “DataRecord” are encoded with the text method:
swe:DataArray definition
= http:sweet.jpl.nasa.gov2.0mathFunction.owlFunction
swe:description Measurement error vs. temperature
swe:description swe:elementCount
swe:Count swe:value
5 swe:value
swe:Count swe:elementCount
swe:elementType name
= point
swe:DataRecord swe:label
Error vs. Temperature swe:label
swe:field name
= temp
swe:Quantity definition
= http:sweet.jpl.nasa.gov2.0physThermo.owlTemperature
swe:label Temperature
swe:label swe:uom
code =
Cel swe:Quantity
swe:field swe:field
name =
error swe:Quantity
definition =
http:sweet.jpl.nasa.gov2.0sciUncertainty.owlError swe:label
Relative Error swe:label
swe:uom code
= swe:Quantity
swe:field swe:DataRecord
swe:elementType swe:encoding
swe:TextEncoding blockSeparator
= tokenSeparator
= ,
swe:encoding swe:values
0,5 10,2 50,2 80,5 100,15 swe:values
swe:DataArray
In this example, each element consists of a record of two values. The array element structure also corresponds to one block so that tuples are separated by block separators
here the ‘,’ character. Since the array is of size 5, there are 5 tuples listed sequentially in the data block, each one composed of the two values of the data record separated by the
token separator. The pattern is “temp,error temp,error …” since values have to be listed in the same order as the fields.
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