- Node access modules always GRANT access and never restrict it. (It is a whitelisting rather a blacklisting system.) If you use two node access modules and one grants access while another does not, access is granted. This may be backwards from what some people would assume and is the reason why it is tricky to get involved with multiple node access modules. It is possible to use multiple node access modules in harmony however if for example they are applied to different content types or are giving out different grant types.
- The four types of possible grants on a node are: view, update, create, and delete. You can use Devel module’s devel_node_access to analyze a node’s node access grants. (Doing so as a non-developer is a good sign that you’ve gotten into trouble with your node access modules and may need to follow the above advice!)
Drupal的权限使用的是一个白名单而不是黑名单，所以一旦用户被授权某项权限，就无法在其他模块进行限制。
但是有人做了对节点权限限制的尝试
http://blog.davereid.net/content/restricted-content-yet-another-different-drupal-node-access-module
