OGC 08-094r1 SWE Common Data Model
In this standard, all requirements are associated to tests in the abstract test suite in Annex A. The reference to the requirement in the test case is done by its URL.
Requirements classes are separated into their own clauses and named, and specified according to inheritance direct dependencies. The Conformance test classes in the test
suite are similarly named to establish an explicit and mnemonic link between requirements classes and conformance test classes. There are formally identified by URL
and described within a tabular format as shown below:
Requirements Class
http:www.opengis.netspecSWE2.0req{req-class-name}
Target Type Description of standardization target type
Dependency
http:www.opengis.netspecSWE2.0req{req-class-name}
8
Copyright © 2011 Open Geospatial Consortium
SWE Common Data Model OGC 08-094r1
6 Requirements Class: Core Concepts normative core
Requirements Class
http:www.opengis.netspecSWE2.0reqcore
Target Type Derived Models and Software Implementations
6.1 Introduction
The generic SWE Common data model defined by this standard aims at providing verbose information to robustly describe sensor related datasets. We define Sensor Data
as data resulting from the observation of properties of virtual or real world objects or features by any type of Observation Procedure See the Observation and Measurements
specification OGC 07-022r1 for a more complete description of the observation model used in SWE.
Sensor related datasets however are not limited to sensor observation values, but can also include auxiliary information such as status or ancillary data. In the following sections,
we will use the term ‘property’ in a broader sense, which does not necessarily imply “property measured by a sensor”.
A dataset is composed of Data Components whose values need to be put into context in order to be fully understood and interpreted, by either humans or machines. The SWE
Common Data Model provides several pieces of information that are necessary to achieve this goal. More precisely, the SWE Common Data Model covers the following aspects of
datasets description:
- Representation
- Nature of data and semantics by using identifiers pointing to external semantics
- Quality
- Structure
- Encoding
This requirement class constitutes the core of this standard. The standardization target types of this core are all models or software implementations seeking compliance with
this standard.
Requirement
http:www.opengis.netspecSWE2.0reqcorecore-concepts-used
Req 1. A derived model or software implementation shall correctly implement the
concepts defined in the core of this standard.
Copyright © 2011 Open Geospatial Consortium
9
OGC 08-094r1 SWE Common Data Model
6.2 Data Representation
Data representation deals with how property values are represented and stored digitally. Each component or field in a dataset carries a value that represents the state of a
property. This representation will vary depending on the nature of the method used to capture the data andor the target usage. For instance, a fluid temperature can be
represented as a decimal number expressed in degrees Celsius i.e. 25.4 °C, or as a categorical value taken from a list of possible choices such as “freezing, cold, normal,
warm, hot”.
The following types of representations have been identified: Boolean, Categorical, Continuous Numerical, Discrete Countable and Textual. The paragraphs below explain
basic features of each of these representation types.
6.2.1 Boolean
A Boolean representation of a property can take only two values that should be “truefalse” or “yesno”. In a sense, this type of representation is a particular case of the
categorical representation with only two predefined options.
Examples
Motion detectors output can be represented by a boolean value – TRUE if there is motion in the room, FALSE otherwise.
OnOff status of a measurement system can be represented by a boolean value – TRUE if the system in on, FALSE if the system is off.
Requirement
http:www.opengis.netspecSWE2.0reqcoreboolean-rep-valid
Req 2. A boolean representation shall at least consist of a boolean value.
The “Boolean” data type detailed in clause 7.2.4 is used to define a data component with a Boolean representation.
6.2.2 Categorical
A categorical representation is a type of discrete representation of a property that only allows picking a value from a well defined list of possibilities i.e. categories. This list is
called a code space in this standard, following ISO 19103 terminology.
The different possible values constituting a code space are usually listed explicitly in an out-of-band dictionary or ontology. This is necessary because each value should be
defined formally and unambiguously, so that it can be interpreted correctly.
10
Copyright © 2011 Open Geospatial Consortium
