86 Co supported by the service then the complete status information of a tasktasking request
shall be provided in the GetTaskResponse. Figure 24 shows exemplary cases.
Figure 24 – Status information returned in the GetTaskResponse for various exemplary taskstasking requests when the state logger conformance class is
supported by the service 7.3.7.5
Exceptions
Requirement http:www.opengis.netspecSPS2.0reqGetTaskResponseexceptions
REQ 65. When an SPS server encounters an error while performing a
GetTask operation, it shall return an exception message as
specified in clause 7.2. In addition, if the minimum storage time of status information for finalized tasks has passed and the
service already removed that information, it shall throw a StatusInformationExpired
exception.
pyright © 2011 Open Geospatial Consortium
Copyright © 2011 Open Geospatial Consortium 87
7.3.7.6 Examples
Clause 9.6 provides example XML instances for the GetTask operation request and response.
7.3.8 DescribeResultAccess Operation
7.3.8.1 Introduction
The DescribeResultAccess operation allows SPS clients to retrieve information on how to access data that was produced by a specific task, or how to retrieve data for a given
sensor that is tasked by this SPS in general. The response can point to:
• a SOS, WMS, WFS • any other OGC Web Service that provides data
• any data file or folder on an ftp server • any data file or file container that is accessible over the Internet
Clients provide the identifier of either a sensor or task to identify the information they are interested in. Table 40 defines the semantics that of both variations.
Table 40 — Semantics of DescribeResultAccess operation request using task or procedure identifier
DescribeResultAccess request
DescribeResultAccess response Applicable Reference
Usage Options see Table 41
including a procedure identifier
References that points to the services providing data for that procedure. The
response contains the base URL to the service. It is then the clients task to
explore all available data.
Primarily useful to learn in advance at which service typesinstances or via
which protocols data is going to be made available.
3, 5
including task identifier
References to the concrete data of the specified task concrete filefolder on a
server, full [OGC] service request that delivers all data etc.
1, 2, 3, 4, 5 option 3 should be
avoided if possible
1
Notes: 1 When providing information about a task, option 3 is the easiest solution for SPS providers but the
hardest for clients. However, in some domains the link to the service might already suffice as additional information and constraints enable clients to create the request for retrieving their data themselves.
Security issues may also require this option to be used.
The result contains one or more reference group elements, which are defined by [OGC 06-121r3], to describe where data is or will be stored.
88 Copyright © 2011 Open Geospatial Consortium
7.3.8.1.1 Reference group usage
Requirement
http:www.opengis.netspecSPS2.0reqDescribeResultAccessreferenceGroupprocedure
REQ 66. If the DescribeResultAccess request contains a procedure
identifier see Table 40, then the response shall contain one or many ReferenceGroups with references to the possible data
storage locationsservices for that procedure.
In most cases a single group will be used, but there are situations that require the usage of multiple groups, as described
further below.
Requirement http:www.opengis.netspecSPS2.0reqDescribeResultAccessreferenceGrouptask
REQ 67. If the DescribeResultAccess contains a task identifier then each
ReferenceGroup shall describe the complete data set that was
gathered for the requested task. Requirement
http:www.opengis.netspecSPS2.0reqDescribeResultAccessreferenceGroupincremental
REQ 68. If an SPS server publishes data gathered for a task
incrementally, then new references shall be added to the according reference groups. Clients can differentiate new
references from those they already received by the identifier provided with each reference.
The reference groups contains all references required to access the data gathered for a specific task once the task is complete. Before, the set of references in a group can be
incomplete, as new references are added whenever new data was published and thus made accessible to clients.
It may happen that all data for a given task will be published towards the end of the lifetime of a task. In this case, a DescribeResultAccess would yield no results before the
status of the task is set to Final. In some cases published data might also be temporarily unavailable due to failures of the data services. Both situations are recognized by this
standard and can be communicated via the DescribeResultAccessResponse to clients.
The main purpose of allowing more than one reference group in a DescribeResultAccessResponse
is to support the provision of data
