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Introduction

The FEWS Schematic Status Display (SSD) Web Service allows requesting SSD displays (formerly called Scada displays) using a simple REST web interface. This web service is available only in FEWS 2019 and later versions.

For more information on configuring SSD/Scada displays, please refer to the SSD configuration page,  The SSD web service uses the same configuration as the FEWS explorer UI and report generator, so for an existing configuration setting up the FEWS SSD web services can use the same region home folder as the FEWS explorer UI without requiring additional configuration.

SSD Request methods

The available request methods with their supported parameters are described here.

GetCapabilties

Get the list of available available SSD 'displays' and 'panels' and additional configuration information that is required to successfully use the SSD web service, like the time step and relative period to use for time 'navigation'. GetCapabilties will return its content as XML. 

Request parameters

  • FORMAT (optional) : the requested capabilities format. ( 'application/xml' or 'application/json')  The default format is XML.
  • SSD : by specifying the name of a SDD display panel the capabilities can be rendered for only one specific SSD display panel.
  • DIMENSIONLIST : when DIMENSIONLIST=TRUE  the time dimension information will include a list of individual time steps. (default is false)

Example request

http://localhost:8080/FewsWebServices/wms?request=GetCapabilities&format=application/xml


Example xml response

<SSD_Capabilities version="1.0.0">
<Service>
	<Name>SSD</Name>
	<Title>Delft-FEWS Schematic Status Display Service (SSD)</Title>
</Service>
<Capability>
	<Request>
		<GetCapabilities>
			<Format>application/xml</Format>
			<Format>application/json</Format>
		</GetCapabilities>
		<GetDisplay>
			<Format>image/svg+xml</Format>
		</GetDisplay>
	</Request>
	<DisplayGroup>
		<Name>ScadaOverzichtsscherm_WMCN</Name>
		<Title>Scada Overzichtsscherm NL</Title>
		<Time>
			<RelativePeriod unit="day" start="-15" end="2"/>
			<TimeStep unit="hour" value="1"/>
		</Time>
		<DisplayPanel>
			<Name>Overzichtsscherm_WMCN</Name>
			<Title>Overzichtsscherm Nederland</Title>
		</DisplayPanel>
		<DisplayPanel>
			<Name>Verwachtingenscherm_WMCN</Name>
			<Title>Verwachtingen Nederland</Title>
		</DisplayPanel>
	</DisplayGroup>
</Capability>
</SSD_Capabilities>

Please note that the used naming conventions are slightly different from those used on the SSD configuration page,  This is because the terms "Scada display" and "Scada panel" are quite closely related to their appearance in the FEWS explorer UI where a FEWS display contains a list of multiple panels a user can choose from. As the SSD Web service has no visual appearance the terms "display" and "panel" become more or less arbitrary. Keeping in mind that a "Scada display" is a group of "Scada panels" (where it is the "Scada panel" that actually displays the Scada/SDD schematic, the name "DisplayGroup" and DisplayPanel" is used instead.  ("DisplayGroup" is equivalent to "ScadaDisplay" and "DisplayPanel" is equivalent to "ScadaPanel").

GetDisplay

Get the SSD display as SVG document for one of the configured SSD "DisplayPanel" items listed in the capabilities XML. The DisplayPanel (Scada panel) to be rendered is specified by name using the SSD parameter.

Request parameters

  • SSD (required): the name of the SSD "DisplayPanel" to render. Only one SSD can be rendered at a time.
  • TIME (optional): the time for which the SSD is to be rendered. Time has to be in the ISO_8601 dateformat:  yyyy-MM-ddTHH:mm:ssZ. The default time is the current time.
  • LANGUAGE (optional): a 2 character language code to use while rendering the SVG file. The language control affects how numbers are formatted, i.e. for language=nl a decimal comma will be used as decimal separator. The default is 'US' for US English.

Response

SVG (Scalar Vector Graphics) image file of the requested SSD display/panel.

Example request

http://localhost:8181/FewsWebServices/ssd?request=GetDisplay&SSD=Overzichtsscherm_WMCN&TIME=2019-07-25T00:00:00Z&LANGUAGE=nl

Example svg response:

Properties

There currently are no specific properties to be configured for the SSD Web service, a clientconfig.xml and global.properties file present in the configured region home folder will be read at starup of the FEWS web services as usual, but not all properties present in these general configuration files will directly affect the SSD web service, for example the default locale used for date/time and number formatting will be US English, regardless of the COUNTRY and LANGUAGE specified in the global.properties file.

Installation

For general FewsWebServices requirements, see: Installation. There are no additional requirements for the FEWS SSD web service.

The tomcat server the FEWS web services are running on should have sufficient memory. When many concurrent users are using the SSD and other services the CPU and memory requirements will increase with the number of SSD displays in a configuration and also depends on the size of the SVG templates used.

Since the SSD service is stateless, it can be scaled both vertically (more cpu and memory) and horizontally (more tomcat instances).


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