WebSphere brand IBM WebSphere Premises Server, Version 6.1.x

Zones

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:
  1. 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.
  2. 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.
Image showing a tag entering and leaving a zone through and exit zone

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:
  1. 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.
  2. 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.
Image showing a zone with gates

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.
  1. 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.
  2. 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.
  3. 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.
Image showing a fully covered 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:

  1. 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.
      Note: This situation is different from the situation described in Monitoring the entry and exit in an area.
    Image showing a scenario where the entry and exit into the zone are fully covered, but there are places within the zone that are not covered
  2. 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:

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.

Image showing outer and inner boundary zones
Image showing outer and inner 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.

Image showing a single boundary zone and an exit zone

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.

Image showing multiple zones and a tagged person walking through those zones.
In the graphic, the arrows represent persons with tags walking through the area. The circles represent points along the path they take:
  1. 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.
  2. 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.
  3. 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.

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