Entity Relationship Diagrams Essay.
This is a unique kind of model that tries to illustrate the relationship that exists between data in a database. The construction of an entity relationship diagram always manipulates symbols to illustrate the relationship between the information contained in that specific database. The rectangular or box like figures are regularly used to represent entities, the diamond figures are normally used to illustrate the affiliation that exist between the information while the ovals are used to embody the elements. Hence in the literature below all this will be manipulated to illustrate what entity relationship diagrams constitute and how it’s are applicable to medicine where there is a relationship between data given by a patient and hospital data and information given by a doctor. This is because the sufficiency of any health center relies on the information that a patient gives and the flow of information that between departments.Entity Relationship Diagrams Essay.
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An entity hence is the space provided in which data will be stored within the database (System) under contemplation. E.g. in the case of medicine, an entity may be named as:
Another element that may constitute a database is the contour that connects two entities that symbolizes the relationship between two entities. The relationship will have attributes that will be showing the affiliation that exists between the data that is connected by the line and has an event that both must be conventional to.Entity Relationship Diagrams Essay.
The line indicated shows the relationship that exists between data that are contained in both entities. It shows a mutual relationship between the two entities: Information of the first entity that is related to the second and that of the second that is related to the first. Hence, in an entity relationship illustration, the main issue is the identification of the traits in different entities and the affiliation that might exist in the information contained in each and actually drawing the affiliation in the form of a diagram that can illustrate a systematic flow. This will show that the aim of the entity relationship diagram has been achieved. That is the identification of the different entities, the information contained, and the relationship that exists in the information contained in each and every entity and being able to make it flow.Entity Relationship Diagrams Essay.
The relationship that is always included in an entity relationship diagrams always mean different things in an entity illustration diagram, hence most of the cardinality restraint are as explained:
A double line shows a sharing restraint, where by both entities set and the shared information must contribute in a minimum of one affiliation in the relationship lay down.
A one sided arrow from one entity to another showing the relationship between the two sets illustrates a key restraint i.e. either of the two entities can contribute in the relationship in at most one trait in the symbiotic affiliation.
A concentrated line (Thick) illustrates that the two entities are embroiled in only one affiliation that is unidirectional from one entity to another.
A line that is underlined shows that it is a unique attribute that is unique to each entity and different information.Entity Relationship Diagrams Essay.
Anne, A. (2000). On the ontological clarity of entity-relationship diagrams: associative object type indicators and weak entity sets. London: University of Queensland.
Elizabeth, H. J. (2010). Requirements Engineering. New York: Springer.
Pericles, L. (1994). Entity-relationship approach– ER ’94: business modelling and re-engineering. 13th International Conference on the Entity-Relationship Approach (pp. 13-16). United Kingdom: Springer.Entity Relationship Diagrams Essay.