关于验证领域几个术语的完美表达

今天看了一段文字，忍不住击节叫好，这是我看到关于authentication领域中针对几个术语最简洁明了的表达了。

• Subject - Security specific user 'view' of an application user. It can be a human being, a third-party process, a server connecting to you application application, or even a cron job. Basically, it is anything or anyone communicating with your application.

• Principals - A subjects identifying attributes. First name, last name, social security number, username

• Credentials - secret data that are used to verify identities. Passwords, Biometric data, x509 certificates,

• Realms - Security specific DAO, data access object, software component that talkts to a backend data source. If you have usernames and password in LDAP, then you would have an LDAP Realm that would communicate with LDAP. The idea is that you would use a realm per back end data source ans Shiro would know how to coordinate with these realms together to do what you have to do.