This topic defines and explains zones, including boundary
zones, and describes how to monitor the entrances and exits of different
classes of zones.
Zones are
designated logical sections within areas that are associated with
those areas and for which rules can be defined. Zones can overlay
each other and are the units on which rules can be performed and on
which counts and statistics for a tag entering or leaving can be calculated.
Zones within an area are defined with the Spatial Management Client and
can be of different types. An entire area can also be considered a
zone. You cannot change its size in the Spatial Management Client and
it is not displayed as a colored region. However, rules can be attached
to it.
Within the IBM® Location Awareness Services for WebSphere® Premises Server system,
zones are used for different purposes. Depending on their purpose,
they are classified into one or several of the following zone classes:
- Alarm zones
- Alarm
zones are the most common type of zone. Access restriction rules or
similar rules can be triggered when an item (usually a person or asset)
enters or exits a zone of this class. The restriction rules can be
set for all other zone types as well, but they have additional semantics,
as described in the following definitions.
- Privacy zones
- Currently
privacy zones behave like alarm zones.
- Shadow zones
- Tags
entering shadow zones might not be visible temporarily because they
are out of reach of the tag reader infrastructure or the signals are
shielded. Location Awareness Services for WebSphere Premises Server assumes
that a tag continues to be in the shadow zone at the last reported
position after it has been seen. No alert is generated if the tag
is no longer visible.
- Boundary zones
- These zones are
used for implementing access control to areas that are not covered
by event devices and therefore cannot be controlled completely or
directly. See Monitoring the entrance and exit of zones that are not fully covered by devices.
Note: In
the
Spatial Management Client,
the term
barrier zone is a synonym for a
boundary zone.
- Exit zones
- These
zones are used to determine if a tag has passed and no signals can
be received thereafter. They indicate that an item has left the premises
and so there is no reason to be concerned about not receiving a signal.
Monitoring the entry and exit in an
area
The following example describes how an item (person
or asset) might be tracked when entering and exiting a zone. Assume
you have X (0.0, 0, 100, 100, and 100) and Y (100 and 0) coordinates
representing the area MyZone. Whenever a tag is visible
within these coordinates and a signal comes from the related hub, Location Awareness Services for WebSphere Premises Server registers
the tag within the zone.
Consider the following scenarios:
- The tag enters the area and follows the path indicated in the
graphic below. If the tag is no longer visible, Location Awareness Services for WebSphere Premises Server stores
information about the last location where the tag was seen (indicated
by the small circle at right edge of the area), and after a configurable
time generates an event indicating that the tag is not responsive
and was last seen at the stored location.
- The tag follows the path in the graphic below and is last seen
in an exit zone. Location Awareness Services for WebSphere Premises Server no
longer displays the tag in the area and recognizes that the tag has
left the area.
So that Location Awareness Services for WebSphere Premises Server knows
that tags have left an area, you should define exit zones. Otherwise Location Awareness Services for WebSphere Premises Server assumes
that the tag is still at the edge of the area, but not responsive
anymore.
Monitoring the entry and exit
in an area (gates)
You can also define one device to be responsible
for reporting the entry or exit to or from an area or zone. Do this
by creating a gate. You define a event provider and then define
a device to monitor the gate. You then specify whether the device
monitors tags that are entering the zone (IN) or tags that are exiting
the zone (OUT). When the device sees a tag that fits the parameter
you specified (IN or OUT), it reports the event and generate an alert
if a rule is broken.
When monitoring zones in areas, define
the gate for the zone and for the area. Otherwise, Location Awareness Services for WebSphere Premises Server cannot
correctly monitor tag counts for the zone and area.
Consider
the following scenario for a zone inside of an area that is not fully
monitored by devices:
- Create one gate to monitor tags with device A that enter the zone.
Define the gate twice, once for the zone and once for the area.
- Create another gate to monitor tags with device B that leave the
zone. Also define this gate twice, once for the zone and once for
the area.
Monitoring zones that are fully covered by devices
The
following graphic depicts a zone in which devices can cover all of
the areas. The following example describes how
Location Awareness Services for WebSphere Premises Server tracks
a tag that follows the path indicated by the arrow.
- When the tag reaches the first point (indicated by a circle), Location Awareness Services for WebSphere Premises Server generates
an event internally that indicates that the tag entered the zone and
checks whether any existing rules apply to the situation. The tag
count for the zone increases by 1.
- Within the FullyCovered zone, Location Awareness Services for WebSphere Premises Server can
usually track the position of the tag continuously. If Location Awareness Services for WebSphere Premises Server loses
contact with the tag, an AtlasTagNotResponsive event
is generated, indicating an abnormal condition. Within the zone, no
location-dependent rules are checked.
- When the tag leaves the zone (indicated by the second circle) Location Awareness Services for WebSphere Premises Server generates
an event indicating that the tag left the zone and checks whether
any existing rules apply to this situation. The zone tag count decreases
by 1 when the tag leaves the zone.

Thus, zones that are fully covered by devices
allow you to fully track the activity of a tag. This type of zone
is usually an alarm zone, where you define business rules for monitoring
activity within the zone.
Monitoring shadow zones
The following scenarios
describe situations in which zones are not completely covered by devices.
Assume you want to monitor a closed room in which the tags
cannot be seen in all sections at all times. For example, the room
might contain metal, which reflects signals in a certain section of
the zone so that signals are too low to register, or a chimney is
located above the devices in one section.
The following graphic
depicts two scenarios:
- The entry and exit for the zone are fully covered:
- Entry to the zone (indicated by the first circle) and exit from
the zone (indicated by the second circle) are covered by devices.
However, there are spots in the zone (indicated as "Not Covered")
where signals from the tag cannot be received.
- Location Awareness Services for WebSphere Premises Server assumes
that a tag continues to be in the shadow zone at the last reported
position after it has been seen. No alert is generated if the tag
is no longer visible.
- The entry into the zone is not fully covered:
In this special
scenario, you must define a zone or zones outside of the entry area
to monitor tags that enter or exit the zone. Solutions include the
following:
- Two boundary zones
- Single boundary zone
- Mixed approach of zones
Monitoring the entrance and
exit of zones that are not fully covered by devices
Some
zones are not fully covered by event devices; however, a precise count
of tags within a zone is still needed. To accomplish this, the entrance
and exit of the zone must be monitored. To monitor these zones, you
define boundary zones around or at the entrance of the zone
to be monitored.
Boundary zones can be related to a target zone
in the following ways:
- Outer boundary zone: The tag is assumed to be out of the
target zone.
- Inner boundary zone: The tag is assumed to be in the target
zone, even it is not visible.
- Single boundary zone: The tag is assumed to be in the target
zone, even it is not visible. However, you do not use an outer boundary
in this case.
As shown in the following figures, target zones can be monitored
by one or more inner and outer boundary zones, or multiple target
zones can share the same inner or outer boundary zones.
You can use a single boundary zone to monitor the entrance of
the target zone and an exit zone to monitor the exit. If no exit zone
is defined, Location Awareness Services for WebSphere Premises Server assumes
that the tag remains in the zone, even though it cannot see it.
Sample zone layout
The following figure combines different
zones in one area. Notice that you can overlap zones. You can open
an overlapping area to see different graphical representations, and
for each zone you can see summary counts for the all child zones of
the area in focus. However, note that you cannot see details for more
than one zone at a time.
In the graphic, the arrows represent persons with tags walking
through the area. The circles represent points along the path they
take:
- A person walks from the left exit zone to the right exit zone,
passing through two zones:
- When the person reaches point A, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the FullyCovered alarm zone.
- When the person reaches point B, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the Subarea alarm zone. Because
Subarea is another zone, if you had imported and defined the image
of the other area, you could navigate to it and see the tag there
as well.
- When the person reaches point C, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the right exit zone. When the tag is no longer
seen in the exit zone, Location Awareness Services for WebSphere Premises Server removes
the tag from the area and assumes that the tag has left the area.
- A person walks from the left exit zone into the shadow zone and
then exits through the left exit zone:
- When the person reaches point D, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the EntryFullyCovered shadow zone.
- When the tag reaches point E, the tag is no longer seen.
Because it is in a shadow zone, Location Awareness Services for WebSphere Premises Server does
not expect the tag to respond and does not generate an alert event. Location Awareness Services for WebSphere Premises Server continues
to assume that the tag is in the EntryFullycovered shadow
zone.
- When the tag reaches point F, the tag is seen by the devices
and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the left exit zone. When the tag is no longer seen
in the exit zone, Location Awareness Services for WebSphere Premises Server removes
the tag from the area and assumes that the tag has left the area.
- A person walks from a privacy zone within the area to the right
exit zone, passing through several zones:
- When the person reaches point G, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the InnerBorder boundary zone.
Because this zone is a border area for the PartlyCovered alarm
zone, Location Awareness Services for WebSphere Premises Server assumes
that the tag is within this area.
- When the person reaches point H, the tag might not be seen
by a device, but Location Awareness Services for WebSphere Premises Server assumes
that the tag is in the area because it was last seen in the InnerBorder boundary
zone. Also, because these zones overlap a shadow zone, the TagNotResponsive alert
event is not issued.
- When the person reaches point I, the tag is seen by the
devices and Location Awareness Services for WebSphere Premises Server knows
that the tag is in the right exit zone. When the tag is no longer
seen in the exit zone, Location Awareness Services for WebSphere Premises Server removes
the tag from the area and assumes that the tag has left the area.