Some problems, called connection traps, may arise when creating an E-R model. The connection traps normally occur due to a misinterpretation of the meaning of certain relationships. There are mainly two types of connection traps:
In a fan trap, a model represents a relationship between entity types, but the pathway between certain entity occurrences is ambiguous. A fan trap may exist where two or more one-to-many (1:N) relationships fan out from the same entity. Fig. 6.19 (a) shows an example of fan trap problem.
(a) An example of fan trap
(b) Semantic net of E-R model
(c) Restructured E-R model to eliminate fan trap