Database Reference
In-Depth Information
Date (result set): In this mode, the X axis value will be automatically set to the
system
￿
s timestamp when the query results arrive. In this case, no inputs for the
X axis are available.
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Date (observation): This mode is designed to work together with a group node.
In this case, additional inputs (xi) will appear on the node for connecting each
series
￿
X axis timestamp data. These inputs accept multiple connections from a
group node
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elds where
connected, the system will automatically generate a timestamp for the X axis
while it processes incoming data. Figure 8 shows an example scenario where a
line chart plots the max temperature for every day.
'
s grp_recordTime
elds. Depending on which time
Pie chart sink node: This type of node renders a pie chart and supports up to ten
(10) series. The
￿
rst step to setting up a pie chart involves the selection of the
number of series. Depending on the number of series selected, additional inputs (y i )
appear on the node for connecting each series
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value.
Meter gauge sink node: This node will render a gauge with a dial indicating its
current value. In order to setup the gauge, one has to provide its measure unit label
and accordingly its minimum and maximum values. The node exposes a single
input endpoint for connecting the gauge
￿
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s value.
￿
Map sink node: The map sink node renders a map containing markers indicating
the location of sensors and optionally renders circle overlays to indicate the mag-
nitude of a speci
c attribute from each sensor. To set up this node one needs to
setup the map widget parameters. To this end, the latitude, longitude and zoom level
properties must be
lled in. Then the type of overlays that should be rendered must
be selected. The following overlay modes are supported:
￿ Markers only: Renders a marker at each sensor
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s location.
Circles only: Renders a circle at each sensor
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s location with a radius equal to
￿
the connected property
property. The max
value scaling factor defaults to one (1) and can be used to tweak the size of the
generated circles.
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s value scaled by the
max value
Markers and circles: This mode combines the previous two modes.
￿
Passthrough sink node: The passthrough sink node is a special node designed to
be used by applications that need to bypass the request presentation layer and
perform their own custom processing on the service data. This node provides a
simple sink with N inputs. The number of inputs is selected by editing the attribute
count property of the node. Once the property is modi
￿
ed, the node will the
appropriate number of input endpoints (attr1, , attrN) depending on the
property value. Once the service has been registered, the application needs to
manually invoke the SDUM to get the service results. When used via the request
presentation layer, the bound attributes are rendered in tabular form.
Using Variable Property Values . Some application scenarios involve queries where
some of the parameters are not known a priori during service design. For example, a
service that reports the availability of a speci
c resource (like a room) near a mobile
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user depends on the user
s location which is only known when the query is to be
executed. To support such scenarios, provide a mechanism for converting node
properties into variables is provided. This mechanism is supported for all nodes except
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