Facts are usually derived from some entity having been “frozen” and captured at a particular status in its lifecycle. The process by which this status is achieved is normally triggered by an event. What do we mean by the term event?
There are two ways of considering the definition of an event. If the data warehouse is viewed in isolation so that the facts that it records are not perceived as related to the source systems from which they were derived, then they can be viewed purely as events that occurred at a single point in time. If, however, the data warehouse is perceived as part of the “enterprise” database systems, then the facts should be viewed within the wider context, and they become an entity preserved at a “frozen” state, having been triggered by an event. Either way, the distinguishing feature of facts is that they do not have a lifespan. They are associated with just one time attribute. For the purpose of clarity the following definition of facts will be adopted:
A fact is a single state entity that is created by the occurrence of some event.
The circumstances and dimensions are derived from what has been referred to as the reference entities within the organization. This is information such as customer, product, and market segment. Unlike the facts in a data warehouse, this type of information does have a lifespan. For instance, products may have various states during their lifespan from new to fast moving to slow moving to discontinued to deleted.
Facts are usually derived from some entity having been “frozen” and captured at a particular status in its lifecycle. The process by which this status is achieved is normally triggered by an event. What do we mean by the term event?
There are two ways of considering the definition of an event. If the data warehouse is viewed in isolation so that the facts that it records are not perceived as related to the source systems from which they were derived, then they can be viewed purely as events that occurred at a single point in time. If, however, the data warehouse is perceived as part of the “enterprise” database systems, then the facts should be viewed within the wider context, and they become an entity preserved at a “frozen” state, having been triggered by an event. Either way, the distinguishing feature of facts is that they do not have a lifespan. They are associated with just one time attribute. For the purpose of clarity the following definition of facts will be adopted:
A fact is a single state entity that is created by the occurrence of some event.
The circumstances and dimensions are derived from what has been referred to as the reference entities within the organization. This is information such as customer, product, and market segment. Unlike the facts in a data warehouse, this type of information does have a lifespan. For instance, products may have various states during their lifespan from new to fast moving to slow moving to discontinued to deleted.