Entity Set

Declaring Keys in ODL

ODL is different from the other models studied so far in that the declaration and use of keys is optional. That is, in the E/R model, entity sets require keys to distinguish members of the entity set from one another. In the relational model, where relations are sets, all attributes

Semistructured Data

The semistructured-data model plays an important role in database systems: 1. It serves as a model appropriate for integration of databases, that is, for describing the data included in two or more databases that include similar data with different schemas.

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