Reasoning with enhanced temporal entity-relationship models

Abstract

Recent efforts in the Conceptual Modelling community have been devoted to properly capturing time-varying information, and several proposals of temporally enhanced Entity-Relationship (ER) exist. This work gives a logical formalisation of the various properties that characterise and extend different temporal ER models which are found in literature. The formalisation we propose is based on Description Logics (DL), which have been proved useful for a logical reconstruction of the most popular conceptual data modelling formalisms. The proposed DL has the ability to express both enhanced temporal ER schemas and integrity constraints in the form of complex inclusion dependencies. Reasoning in the devised logic is decidable, thus allowing for automated deductions over the whole conceptual representation, which includes both the ER schema and the integrity constraints over it.

Anchor modeling — Agile information modeling in evolving data environments

“…it corresponds to the concept of valid time [1,6,15] as discussed in the previous paragraph. In Anchor Modeling, this interval is defined using a single time point.…”

“…Recording time in Anchor Modeling corresponds to the concept of transaction time [1,6,15] discussed earlier. Loosely speaking it can be said to be the time when a certain piece of information is entered into the domain of discourse, or "the time (period) during which a fact is stored in the database" [15].…”

“…Database modeling approaches, such as the original ER model, do not include specific language elements that explicitly support temporal concepts. Extensions [9] to ER schemas encompass temporal constructs such as valid time, the time (interval) in which a fact is true in the real world, and transaction time, the time in which a fact is stored in a database [1,6,15]. Anchor Modeling provides syntax elements for representing the former, i.e.…”

“…A composite unique clustered index should be created on the foreign key column in ascending order together with the historization column in descending order. 1 This means that on the physical media where the table data is stored, the latest version for any given identity comes first. This will ensure more efficient retrieval of data since a good query optimizer will realize that a sort operation is unnecessary.…”

Diseño de un Almacén de Datos Históricos en el marco del desarrollo de software dirigido por modelos

“…Por otro lado, la ventaja del enfoque explicito es la denominada compatibilidad ascendente; esto es, el significado de los modelos ER convencionales (legados) utilizados en los modelos temporales permanecerá inalterable. Esto es importante, por ejemplo, en el modelado de DW y bases de datos federadas, donde los datos fuente pueden ser tanto provenientes de TDB como de bases de datos legadas [AF99].…”