What are the different classes of Digital Signature Certificates?

In addition to four classes of certificates given below, the Certifying Authority may issue more classes of Public Key Certificates, but these must be explicitly defined including the purpose for which each class is used and the verification methods underlying the issuance of the certificate. The suggested four classes are the following :-

        Class 0 Certificate: This certificate shall be issued only for demonstration/ test purposes.

        Class 1 Certificate: Class 1 certificates shall be issued to individuals/private subscribers. These certificates will confirm that user's name (or alias) and E-mail address form an unambiguous subject within the Certifying Authorities database.

        Class 2 Certificate: These certificates will be issued for both business personnel and private individuals use. These certificates will confirm that the information in the application provided by the subscriber does not conflict with the information in well-recognized consumer databases. 

        Class 3 Certificate: This certificate will be issued to individuals as well as organizations. As these are high assurance certificates, primarily intended for e-commerce applications, they shall be issued to individuals only on their personal (physical) appearance before the Certifying Authorities.