WebSphere brand IBM WebSphere Premises Server, Version 6.1.x

Planning for classes and items

This topic describes how to plan effectively for Location Awareness Services for WebSphere® Premises Server classes and items.

To plan effectively for Location Awareness Services for WebSphere Premises Server classes and items, consider some basic rules and concepts behind the Location Awareness Services for WebSphere Premises Server classes as described below.

Class structure

When defining classes and items, start by defining your class hierarchy along with attributes and properties. Then, you can associate items with the classes. Location Awareness Services for WebSphere Premises Server classes make up a hierarchical tree, so remember the following:
  • When you delete a class, it also deletes all subclasses and items belonging to the deleted class or subclass.
  • When you add a subclass, it inherits all properties from the parent class. These inherited properties cannot be changed at the subclass level.
  • When maintaining class properties, keep the following points in mind:
    • Make sure you identify whether subclasses have been defined for the class and whether items were defined for the class or subclass.
    • Make sure you use unique property names throughout the class hierarchy. For example, if the class Employee has a property named BadgeNumber and if the subclass, SecurityPersonnel, represents guards who have special badges in addition to the normal employee badge, give the special badge number a unique property name such as SecurityBadgeNumber.
    • Changes to key properties are restricted when the class or subclass has items defined. Therefore, the following restrictions apply:
      • Adding key properties is allowed only if no items are defined for the class or any of its subclasses.
      • Deleting key properties is allowed only if no items are defined for the class or any of its subclasses.
      • Changes to key properties are usually allowed only if they are less restrictive.
      • Renaming key properties is allowed.
      • You can only change a key property type from any value to a string. The values are kept.
    • Changes to other properties are restricted when the class or subclass has items defined. Therefore, the following restrictions apply:
      • Adding other properties is allowed only if no items are defined for the class or any of its subclasses.
      • Deleting other properties is allowed only if no items are defined for the class or any of its subclasses.
      • Changes to other properties are usually allowed only if they are less restrictive.
      • Renaming other properties is allowed.
      • You can only change a property type from any value to a string. The values are kept.
      • Changing a property from mandatory to optional is allowed, but you cannot make an optional property mandatory.
  • Minimize the number of levels in your class hierarchy. Too many levels can make the display unusable and can decrease performance.

Class name length

Depending on font size and screen resolution, long class names might be truncated in the Spatial Management Client and Location Awareness Services for WebSphere Premises Server Administrative Console.

Subclasses are shown with an indentation that depends on the level in the class hierarchy. In order to display the full names, use the following guidelines:
  • Top-level classes should not be longer than 15 to 20 characters (depending on your resolution).
  • The name length should decrease by about 20 percent per level.

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