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Does the double line in the following ER diagrams means total participation or recursive relation?

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Could anyone tell me the notation difference for both?

Amir
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mko
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3 Answers3

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Total Participation: Every entity in the set is involved in some association (or tuple) of the relationship.

Recursive Relationship: An entity set relating to itself.

Most commonly in recursive relationships they indicate the different types of roles an entity can have (e.g., the different ways it can participate) in a relationship by writing each role above each line.

An example of this would be in a Course table with a relational table of Prerequisites

A Course could be both the Prerequisite and the Course and you would write those on each line.

Here's another example.

Assuming your textbook follows a similar pattern, I would assume that these are in fact total participation constraints.

formatkaka
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Eric Hotinger
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  • So the double lines in all three are totally participation? – mko Nov 05 '13 at 12:58
  • That's what I would assume since they don't have the words on each line. But, if I were you, I would go through your textbook when they first introduce the notation and double check. It's hard to know the semantics of the textbook. – Eric Hotinger Nov 05 '13 at 12:59
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double line : Used to represent total participation of an entity in a relationship set.

A recursive relationship is one in which the same entity participates more than once in the relationship.

recursive relationship example : Suppose one team is assigned the task of supervising the other teams. This supervisor team makes sure that each team records its portion of the data. The supervision relationship is a recursive relationship because the same entity, a particular team, participates more than once in the relationship, as a supervisor and as a supervisee. To draw the situation, we label the two lines between team and supervision with the two possible roles

by this definitions all three above are total participation

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Amir
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defination of total participation constraints: the participation of an entoty set E in the eelationship R is said to be a total if every entity in E participates in at least one relationship in R.