What ensures the integrity of data within an attribute domain?

The integrity of data within an attribute domain is primarily ensured by the set of allowable values for the attributes. This set defines what can be entered into the database for specific fields, thereby limiting the values to those that are valid and meaningful. For instance, if an attribute is defined to hold only integers between 1 and 100, it prevents any input that falls outside this range, such as letters or numbers larger than 100. This strict adherence to predefined values helps maintain data quality and ensures that the data remains consistent and reliable for analysis and reporting.

On the other hand, while access controls and data validation rules contribute to data integrity, they do so in different ways. Access controls restrict who can modify the data but don't specify what that data should be. Data validation rules provide guidelines for acceptable data forms but don't limit values strictly in the same manner as an attribute domain. Encryption techniques focus on securing data but do not impact its integrity regarding validity or appropriateness within a specified domain. Thus, the correct choice highlights how defining a clear set of allowable values is crucial for maintaining the integrity of the data.