Chapter 23: Problem 10

Describe the multilevel relational data model. Define the following terms: apparent key, polyinstantiation, filtering.

Short Answer

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The multilevel relational data model extends the standard relational model for databases that require multilevel security. An apparent key is a primary key that doesn't necessarily uniquely identify each tuple. Polyinstantiation enables the existence of data at varying classification levels. Filtering selects data based on certain conditions, controlling data presented to a user.

Step by step solution

Defining Multilevel Relational Data Model

A multilevel relational data model is an extension of the standard relational model, which is used for databases with multilevel security. It represents data at different classification levels and satisfies the principles of multilevel secure systems. Each tuple in a multilevel relation is associated with a classification level, and each cell in a tuple with a sensitivity level.

Explaining Apparent Key

An apparent key is a key attribute that is used as a primary key for a relational database, but it does not necessarily uniquely identify each tuple in the relation. It is typically used in multilevel secure databases where different values may exist for the same primary key at different security levels.

Defining Polyinstantiation

Polyinstantiation is a principle in multilevel security that allows different versions or instances of data to coexist at different classification levels. It occurs when a lower security level user is prevented from inferring the existence of a higher security level data by allowing the same key to relate to different data at different levels. For example, when querying the database, the same query can produce different results depending on the user's security level.

Understanding Filtering

Filtering in the context of databases, refers to the process of selecting specific data from a database based on certain conditions. This can be used to control the results that are presented to a user, ensuring that they only see the data that is relevant to them, or that is within their security clearance level. This allows databases to control the types of data that different users can access, enhancing security and efficiency.

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Describe the multilevel relational data model. Define the following terms: apparent key, polyinstantiation, filtering.

Short Answer

Step by step solution

Defining Multilevel Relational Data Model

Explaining Apparent Key

Defining Polyinstantiation

Understanding Filtering

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