Frequently Asked Questions


1.

Why can I not change the value of a property if it has the KEY qualifier?

from a philosophical viewpoint, because it is the combination of values of the key properties that defines a particular instance. if the value of a key property changes then you have created a new instance. from a practical viewpoint, the wbem server will use the values of the keys to store instances in such a way that they can be efficiently retrieved. changing a key of an instance already created would be very difficult to handle.

2.

How can I create a unique opaque key the InstanceID?

this varies from application to application. the simplest, but often impractical, technique is to have a central authority which issues an incrementing number. it can ensure that the same number is never issued twice. if this is impractical look for a base number which is guaranteed to be globally unique, a mac address, for example. then combine this with something which is locally unique, a slot number or user identity, for example. together these could form a unique key.

Answers

1.

From a philosophical viewpoint, because it is the combination of values of the key properties that defines a particular instance. If the value of a key property changes then you have created a new instance.

From a practical viewpoint, the WBEM server will use the values of the keys to store instances in such a way that they can be efficiently retrieved. Changing a key of an instance already created would be very difficult to handle.

2.

This varies from application to application. The simplest, but often impractical , technique is to have a central authority which issues an incrementing number. It can ensure that the same number is never issued twice.

If this is impractical look for a base number which is guaranteed to be globally unique, a MAC address, for example. Then combine this with something which is locally unique, a slot number or user identity, for example. Together these could form a unique key.




A Practical Approach to WBEM[s]CIM Management
A Practical Approach to WBEM[s]CIM Management
ISBN: 849323061
EAN: N/A
Year: 2006
Pages: 152

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