Identifying instances across datasets
Before you can compare or merge different versions of an entity, you must determine that they indeed represent the same entity. You must identify each instance.
The Identify activity accomplishes this matching by applying rules that you specify against instances of the same class in different datasets. For example, a rule to identify computer system instances might specify that the IP addresses of the instances be equal.
When the rules find a match, both instances are tagged with the same reconciliation identity, an extra attribute that shows that they each represent the same item in their respective datasets.
You can also manually identify instances that were not identified by rules in an Identify activity.
To identify instances, you must create an Identify group for each participating dataset. In this group you must create Identify rules that attempt to match instances of a particular class in that dataset against instances in all other participating datasets. For example, to compare datasets A, B, and C you need the following groups: one each to match A against B and C, B against A and C, and C against A and B.
To identify data in different classes based on different criteria, you must create more Identify groups. Because the subclasses of the specified class inherit the groups, if your data is sufficiently normalized, you could specify groups only for the base class
You then create an Identify activity and associate the Identify groups to it. Designate one of the participating datasets as the master dataset, meaning that the reconciliation identity of its instances is applied to matching instances in the other datasets, which are known as auto-identify datasets. If the instance in the master dataset does not have an identity, one is automatically generated.
If you identify a class between datasets that are poorly normalized and you cannot find attributes of the class itself on which to match, you can match on an attribute of a source CI if a weak relationship exists and has any propagated attributes. For example, if you always give a disk drive a
BMC_HostedSystemComponent relationship to the computer system where it is installed, you can match two disk drives because their source computer systems have the same name, because
BMC_HostedSystemComponent propagates the
Name attribute from system to component.
For more information about identifying, see Matching instances across datasets by using a reconciliation Identify activity.