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Figure 6-11: Publish-Find-Bind Pattern
The publication of resources of the resource provider to the resource broker may follow either a push or a pull paradigm. In a push paradigm the meta-information entries are created,
updated and deleted by actively calling corresponding operations of the catalogue service. In this case, the resource providers act in a client role. In a pull paradigm, the resource broker
acts in a client role and retrieves meta-information e.g. the capabilities documents of resource providers by calling corresponding operations of the resource providers. The SANY
catalogue service supports both paradigms.
The following outlines what spectrum of resource types need support for discovery in a sensor service network. Discovery policies, typical catalogue queries and the service
interaction patterns that realise the typical queries are presented in section 10.2
6.6.3.2 Resource and Catalogue Types
The discovery process is designed such that it may discover resources of any type that are possibly available in a geospatial resource network. However, this specification focuses
particularly on the resource types that are specific to a SANY Sensor Service Network. The main resources to be discovered follow the concepts that are defined by the information
model about Observations and Measurements see section 7.2. This model also describes the relations between the different types of resources.
The discoverable resource types are
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feature of interest FOI that represents the observation target,
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observed property of a FOI that describe the phenomenon to be observed,
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procedure which encompasses sensors but also algorithms or simulations,
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observation about the phenomenon that has been generated by the procedure.
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service types and instances which deal with the resources listed above. Examples are services to obtain observations Sensor Observation Service, see section 8.2.2 and
services to influence the way the measurement is taken Sensor Planning service, see section 8.2.3, and
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sensor networks as a container for a set of interconnected sensors procedures.
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It is important to distinguish between a resource type and an individual physical instance of a resource. A user may query for all observations processed by a specific method.
In this case the user references a resource type. The user may also be interested in all observations that are provided by a specific physical sensor. In the latter case the user
references a physical instance of a resource.
Usually, there is no direct access to physical sensors in a SANY Sensor Service Network. Instead, resource providers usually service instances act as surrogates for physical
sensors. It is important to note that more than one service instance may contain different views of the same instance of a resource e.g. a sensor or an observation. Each service
provides meta-information about itself and the resources it handles. For example a Sensor Observation Service provides meta-information about its own instance e.g. service provider
but also on the FOI, the observable properties and the procedure used.
A catalogue, i.e. an instance of the Catalogue Service see section 8.2, acts as the primary resource broker in discovery models. Table 6-5 shows several types of catalogues
depending on the set of meta-information about resources types that are stored in the catalogue. Note that the term sensor in this table is used according to the SANY sensor model,
including physical devices but also simulation models as defined in section 5.
The meta-information schema is described in detail in section 7.6.3 as part of the Information Viewpoint of the SensorSA.
Catalogue Type
Description
Full Catalogue catalogue containing information about all defined resources types
Feature Type Catalogue
catalogue containing definition of the feature types, feature attributes and feature associations occurring in one or more sets of geographic
data, together with any feature operation that may be applied see ISO 19110:2005, but referred to there as a feature catalogue
Property Type Catalogue
catalogue containing definition of the property types including at least their identifiers, their names and human-readable descriptions
possibly in multiple languages, semantics, synonyms and default units
Sensor Type Catalogue
catalogue containing definition of the sensor types including their classification scheme, their names and human-readable descriptions
possibly in multiple languages and references to property types made available by a sensor of this type
Sensor Catalogue catalogue containing information about instances of sensor types available in a SANY Sensor Service Network.
Service Catalogue catalogue containing information about instances of service types available in a SANY Sensor Service Network.
Table 6-5: Catalogue Types in a SensorSA
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6.6.4 Sensor Planning
