What does it mean to be related? How do you define a relation's properties?

Suppose you are going to design an instant messaging application called Telegraph. Telegraph is a modularized application composed of UI module, Chat module, and Contact module. The UI module uses the Chat module and the Contact module to render the user interface. The Chat module deals with sending and receiving messages. The Chat module uses the Network module for network communication. When users send/receive messages via the network, the Chat module uses the Crypto module to encrypt/decrypt the message. The Contact module manages the contact list. It also uses the Crypto module for encryption/decryption. The Crypto module uses the Math module for calculation. Now we propose a metric to measure the stability of modules. Formally, we define the "stability" of a module i as Si = a+dut where di" (i.e., incoming connection or dependency) is the number of modules that directly or indirectly USES module i and d?ut (i.e., outgoing connection or dependency) is the number of modules that…

C++ What is relation? Define the properties of a relation.

Here we explain three cases when it makes sense to use a surrogate key in lieu of the relation's main key.

What three situations make it necessary to make a substitute key instead of the main key of a relation?

What are three cases when a surrogate key might be used in place of a relation's main key?

What are three signals that a surrogate key should be generated for the primary key of a relation instead of using the main key?

Primary key identifies a unique tuple of a relation, true or false?

TF (c) If a relation is not in BCNF, then it has at least three attributes in the schema.

Explain three situations under which a surrogate key for the main key of a relation should be established.