References to WMO and ICAO Technical Regulations within this XML schema shall have
no formal status and are for information purposes only. Where there are differences
between the Technical Regulations and the schema, the Technical Regulations shall
take precedence. Technical Regulations may impose requirements that are not described
in this schema.
«Leaf» package for the 'Observable Property Model'
Schematron validation
An 'observable property' is a physical property that can be observed. Typically, this
will be a quantitative property (Quantity [1]) such as 'dew-point temperature'. This
abstract class enables either a single physical property to be specified or a composite
observable property that aggregates a set of physical properties for a given observation
context. In many cases, the observed physical property will be sourced from a controlled
vocabulary, thesaurus or ontology. [1] Quantity: property of a phenomenon, body,
or substance, where the property has a magnitude that can be expressed as a number
and a reference (from the 'International vocabulary of metrology' [http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf])
The attribute 'label' provides the primary human-readable label describing the observable
physical property.
The attribute 'altLabel' provides an alternative human-readable label used to describe
the physical property.
The attribute 'notation' provides a notation or code-value that is used to identify
the physical property within a given context.
CompositeObservableProperty provides a single object within which a number of AbstractObservableProperty
instances can be aggregated.
CompositeObservableProperty: Attribute 'count' shall specify the number of observed
physical properties (specified via the 'property' association role) aggregated within
this composite observable property.
An 'observable property' is a physical property that can be observed. Typically, this
will be a quantitative property (Quantity [1]) such as 'dew-point temperature'. In
many cases, the observed physical property will be sourced from a controlled vocabulary,
thesaurus or ontology. The definition may be a simple a SKOS Concept or a node in
a well-defined ontology. As such, the attributes of ObservableProperty have been elided;
we simply need to assert that the entity has compatible semantics with the ObservableProperty
class defined herein. [1] Quantity: property of a phenomenon, body, or substance,
where the property has a magnitude that can be expressed as a number and a reference
(from the 'International vocabulary of metrology' [http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2008.pdf])
The class 'QualifiedObservableProperty' describes an observable physical property
that is qualified or constrained within a given measurement context. Qualification
of the observed physical property may take several forms: - a specific unit of measure;
- a statistical operator (e.g. maximum) plus the aggregation context that the statistical
operator applies to; or - a constraint (e.g. radiance in wavelength band 50nm to 100nm).
QualifiedObservableProperty: unitOfMeasure shall be appropriate for baseProperty
The attribute 'uom' specifies the unit of measure used in the measurement of this
physical property.
The class 'ScalarConstraint' allows an observed physical property to be constrained
according to specific values of the constraining property. For example, the base property
'air temperature' may be constrained such that we are concerned only with the air
temperature at 2.0 metres above local ground level (e.g. a screen temperature). In
this example, 'height above local ground level' is the constraint property.
ScalarConstraint: unitOfMeasure shall be appropriate for constraintProperty
The attribute 'uom' specifies the unit of measure used in the specification of the
constraint property value.
The attribute 'value' provides the value of the constraint property.
An observed physical property may be represent a statistical summary with respect
to a base property; e.g. maximum UV index over a 3-hour period. The class 'StatisticalQualifier'
defines the type of statistical function plus the mechanism that is used to aggregate
the base property values to create the statistical summary: length, area, volume,
duration or other. Statistical summary properties may be defined by chaining a set
of statistical operations together. For example: mean daily maximum temperature over
a month period comprises two statistical operations with respect to the base property
'air temperature' - (i) maximum over a 24-hour duration, (ii) mean over a 1-month
duration.
The attribute 'description' provides a textual description of the statistical qualification
applied to the base observable physical property.
The attribute 'aggregationArea' defines the spatial area over which the statistical
function is applied in order to determine the statistical summary.
The attribute 'aggregationLength' defines the spatial length over which the statistical
function is applied in order to determine the statistical summary.
The attribute 'aggregationTimePeriod' defines the temporal duration over which the
statistical function is applied in order to determine the statistical summary.
The attribute 'aggregationVolume' defines the spatial volume over which the statistical
function is applied in order to determine the statistical summary.
The attribute 'otherAggregation' defines the any type of aggregation (other than duration,
length, area or volume) over which the statistical function is applied in order to
determine the statistical summary; e.g. prevailing visibility is [approximately] defined
as a mean visibility in each horizontal direction.
The attribute 'statisticalFunction' defines the type of statistical function that
is applied to the base observed property values in order to generate the statistical
summary.
The class 'CategoryConstraint' enables a category-based constraint to be specified.
For example, in aviation the only clouds of significance for terminal aerodrome operations
are convective clouds (cumulonimbus, towering cumulus etc.). The observed physical
property 'cloud base [height]' may be constrained such that it is applicable only
to clouds of a given type. In this example, a single instance of CategoryConstraint
would be defined referencing both cloud types (cumulonimbus and towering cumulus);
'cloud type' is the constraint property.
The attribute 'value' defines the category member that applies to this constraint.
The class 'RangeConstraint' allows an observed physical property to be constrained
according to a range of values of the constraining property. For example, the base
property 'radiance' may be constrained such that we are concerned only with the radiance
between wavelengths of 50nm to 100nm. In this example, 'wavelength' is the constraint
property.
RangeConstraint: unitOfMeasure shall be appropriate for constraintProperty
The attribute 'uom' specifies the unit of measure used in the specification of the
constraint property value.
The association role 'value' references an instance of the RangeBounds class that
specifies the extreme limits of the range that apply to the constraint property.
The class 'Constraint' enables the constraints relating to an observable physical
property in a given measurement context to be specified.
The attribute 'description' provides a textual description of the constraint applied
to the base observable physical property.
The class 'RangeBounds' describes the extreme limits of a property value range (also
known as a property value interval).
RangeBounds: The extreme lower limit of the range of interval must be less than the
extreme upper limit.
The attribute 'rangeStart' provides the extreme lower limit of the range or interval.
The attribute 'rangeEnd' provides the extreme upper limit of the range or interval.
«Enumeration» 'ComparisonOperator' defines the set mathematical operators that may
be used to compare numerical values; not equal, less than, less than or equal, equal,
greater than or equal and greater than.
Comparison operator: "not equal to"
Comparison operator: "less than"
Comparison operator: "less than or equal to"
Comparison operator: "equal to"
Comparison operator: "greater than or equal to"
Comparison operator: "greater than"
http://codes.wmo.int/grib2/codeflag/4.10
any
The «CodeList» class 'StatisticalFunctionCode' specifies the type of statistical function
that is applied to the base observable property to define the statistical summary;
e.g. maximum air temperature. Note that WMO provides two code-tables listing statistical
operators: - WMO No. 306 Vol I.2 Part B FM 92 GRIB code-table 4.10 'Type of statistical
processing'; and - WMO No. 306 Vol I.2 Part B FM 94 BUFR code-table 0 08 023 'First-order
statistics' The GRIB2 code-table is defined as the 'recommended' vocabulary for this
«CodeList» class but lacks some of the necessary terms. For example, the GRIB code-table
includes 'Average' but does not include 'Mean', 'Mode' or 'Median' (which can be found
in the BUFR code-table). However, the BUFR code-table is _NOT_ chosen because 'Accumulation'
is entirely missing. Given that 'extensibility' is set to 'any', authors are free
to refer to their preferred 'statistical operator' vocabulary. The GRIB code-table
is only a recommendation.
vocabulary: http://codes.wmo.int/grib2/codeflag/4.10
extensibility: any