SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
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10. Engineering Viewpoint
10.1. Overview
Based on the major concepts of the SensorSA, the specification of information models and services in the Information and Service Viewpoint of a SensorSA, the following sections provide
definitions of policies for the set-up and operation of sensor service networks.
Policies are defined for the following aspects:
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resource discovery see section 10.2
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sensor and service monitoring see section 10.3
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sensor planning see section 10.4
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access control see section 10.5
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processing of quality information see section 10.6
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handling of large data sets see section 10.7
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cascading sensor observation services see section 10.8
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processing and fusion support see section 10.9
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integration of mobile sensors see section 10.10
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event handling see section 10.11
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plug-and-measure support see section 10.12 Here, the SensorSA follows the basic idea of the RM-OA, 2007 to consider qualifying
characteristics of a service network in terms of policies.
10.2. Resource Discovery Policy
10.2.1 Introduction
The process of resource discovery may be carried out in multiple ways. However, for a given service network it has to be specified in detail in order to enable interoperability.
If not otherwise specified, a sensor service network is qualified as a “mediated service
network” and follows the policy of a “centralised discovery”. According to RM-OA, 2007 this means that there shall be a distinguished instance of a catalogue service in the following simply
called the “SANY Catalogue” or simply “the catalogue” that serves as the discovery entry point to a sensor service network. The meta-information schema of the SANY catalogue is specified in
section 7.6.3.
SANY D2.3.4 Specification of the Sensor Service Architecture V3 Doc.V3.1
Copyright © 2007-2009 SANY Consortium Page 174 of 233
In the following, the service interactions for resource discovery i.e. querying of the catalogue and underlying services and for resource registration i.e. creating and updating of
catalogue entries are specified in more detail as illustrative examples.
10.2.2 Query Models
The queries may be executed in one step or may be broken down into several queries. The first query is always sent to the SANY Catalogue. The sequence of queries may follow one of the
following two basic query models:
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query chaining In the case of query chaining, queries are executed in different steps that are controlled by
the resource requestor. Each step reduces the result set of possible resources. Between two steps the resource requester may process the result of the previous step and decide
how to continue with the next step. The result from the previous query is typically passed as an argument a condition for the next query. The queries in the different steps may be
sent to the resource brokers of the same type homogeneous queries or to resource brokers of different types heterogeneous query. Typically a service has the role of a
resource provider for the previous step and acts as a resource broker for the next step.
Example: The first query returns a set of SOS instances, and the next step uses the meta- information of the SOS by calling getCapabilities to query for resources within the SOS.
Note: Query chaining may be implemented for a predefined application purpose using service chaining if no user interaction is needed.
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query cascading In the case of query cascading queries are broken down into sub-queries that are
individually sent to one or more other resource brokers of the same or of different types, after which the results are assembled into one result set. In contrast to query chaining,
query cascading is transparent to the resource requester. Instead of having all meta- information available to process a query, the resource broker relies on meta-information
entries of additional resource brokers
10.2.3 Typical resource discovery policies
