Polyinstantiation

Polyinstantiation in the information technology world is database-related SQL (structured query language) terminology. It allows a relation to contain multiple rows with the same primary key; the multiple instances are distinguished by their security levels. It occurs because of mandatory policy.

Consider the following table, where primary key is Name and ʎ(x) is the security level:

Although useful from a security standpoint, polyinstantiation raises several problems:
- Moral scrutiny, since it involves lying;
- Providing consistent views;
- Explosion in the number of rows;

In cryptography, polyinstantiation is the existence of a cryptographic key in more than one secure physical location.