In databases the smallest unit of information is a data and the smallest unit of knowledge is the value which belongs to that data, knowledge which is provided by the metadata stored in the Database Management System.
If the database is built from a conceptual model, knowledge is derived from this level of abstraction which provides meaning to data sets which form a logical structure of registration and also lend meaning to possible links between registers. But this knowledge is external from the database and physically separated from it.
In the case of longitudinal fact bases the minimum unit of information is a fact. And a fact is the expression of basic knowledge. Therefore, a longitudinal fact base should be understood as a kind of knowledge base, in which the knowledge is facts.
In general terms a fact is perceived as something that has happened. In our case we restrict ourselves to the results of the implementation of a protocol on an object that appears as a change of state of the object. This change of state itself will generate information that is displayed as part of the fact.
More formally a fact may be considered as a triplet consisting of a protocol that has been executed, the object on which it was implemented and the data, possibly null, which was obtained by the implementation. More specifically a concrete fact is constituted by the execution of a protocol which is the instance of a default protocol, an instance that has been executed on an object state and the data that is a fact of that state.
The system recognizes and distinguishes topicality with the intention of enhancing the effectiveness of access to information.
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