by Joshua L
This article that I chose went over the introduction of a temporal extension to the EER model and the query language GORDAS. The authors introduced the idea of lifespan to an entity by using a temporal element. Temporal attribute values were defined to be functions from the time domain to the attribute domain of an entity. They then presented the concepts of temporal selection conditions and temporal projections. Temporal selection conditions can be used to select entities from an entity set based on their temporal properties. Temporal projections are used to project the attributes of selected entities over a certain time interval for display. The authors also discuss temporal aggregation functions, which are statistically independent to the regular types of aggregation functions used in non-temporal data models.
This article was interesting because it introduces the use of a temporal attribute to allow the ability to view a more specific history of an entity based on time. The article uses the example of wanting the history of each instructor only when that instructor was an assistant or associate professor. I think that this type of manipulation of the EER model could be exceptionally useful for certain organizations to be able to go through the history of a person’s interests and purchases during certain times or parts of their life to be able to more accurately market certain products for certain times.
This article is pertinent to class lecture for this week because it introduces an extension to the Enhanced ER model we covered in class. It adds the element of time or lifespan to the Enhanced ER model.
Elmasri, R.; Wuu, G.T.J.; , “A temporal model and query language for ER databases,” Data Engineering, 1990. Proceedings. Sixth International Conference on , vol., no., pp.76-83, 5-9 Feb 1990 doi: 10.1109/ICDE.1990.113456