SPS Application Profile for EO Sensors OGC 07-018r2
Copyright © 2008 Open Geospatial Consortium, Inc. All Rights Reserved.
17
8. Shared aspects
8.1. Unit of Measure
There are two ways for specifying the Unit of Measure in SWE
Quantity
and
Count
elements: -
Use the xlink:href attribute swe:Quantity
swe:uom xlink:href
= urn:ogc:def:unit:percentage
swe:Quantity -
Use a UCUM code [NR15] swe:Quantity
swe:uom code
= ””
swe:Quantity Whenever possible, using UCUM code is the recommended way of specifying the Unit Of
Measure.
8.2. notificationTarget versus WS-Addressing asynchronous operations
The SPS standard imposes a mandatory
notificationTarget
parameter used to identify the Web Notification Service that will send notifications to the client in case of asynchronous operations.
In the HMA context, SOAP with WS-Addressing protocol has been chosen for the following reasons:
Asynchronous Web Services based on SOAP with WS-Addressing are easily integrated into BPEL workflows
WS-Addressing is a W3C recommendation http:www.w3.org2002wsaddr
WS-Addressing defines a standard for incorporating message addressing information into web services messages
WS-Addressing defines standard ways to route a message over multiple transports or direct a response to a third party. For example, a client application might send a request
over JMS and ask to receive the response through e-mail or SMS
http:dev2dev.bea.compuba200501ws_addressing_intro.html
WS-Security can be used with WS-Addressing
WS-Addressing is easy to implement
In the message, there is a physical separation between the notification stuff in the header of the message and the OGC request in the body. It facilitates the creation of
multi layers applications in which communication i.e. notifications and service specific requests processing are managed in different layers.
Any synchronous request of any existing service can become asynchronous without any modification of the request by adding a replyAddress in the header.
Therefore in the EO profile the
notificationTarget
parameter has been removed.
SPS Application Profile for EO Sensors OGC 07-018r2
Copyright © 2008 Open Geospatial Consortium, Inc. All Rights Reserved.
18 The header of a SOAP message using WS-Addressing contains a
messageID
and a
replyAddress
:
The response is sent asynchronously to the address specified in the
Address
element of the header. The header of the SOAP response message contains a
relatesTo
element for the
messageID
, allowing the client to link the request and the asynchronous response :
Examples of synchronous and asynchronous operation requestsresponses encapsulated into SOAP messages are given in the annex B.
8.3. Acknowlegments
