An algorithm that verifies whether a given subset has sum zero is a "verifier". The proof is passed to the verifier, which verifies it. AVS verifies the numeric portions of a cardholder's billing address. In software testing, conformance testing verifies that a product performs according to its specified standards. Inspection of vendor documentation or spec sheets also verifies requirements. Before executing a class, the Sun JVM verifies its Java bytecodes (see bytecode verifier). This effort verifies that the requirement has been implemented correctly. Windows also periodically verifies the hardware to check for changes. This verifies the weld as correct to procedure prior to nondestructive evaluation and metallurgy tests. CHAP periodically verifies the identity of the client by using a three-way handshake. The CFIA verifies that federal slaughter establishments are compliant with the Meat Inspection Regulations. The JVM verifies all bytecode before it is executed. EFSA currently verifies all functional foods claims. System Testing verifies that functional and non-functional requirements have been met. It also verifies the aforementioned fact about the maximum likelihood estimate of the mean.