drupal access stages

Drupal is built with permission sets in mind.
User may have 1 or more roles.
Content may be limited based on content type, or up to single node level (1record).

When a user is viewing a node / page,
user will have to pass through access "access content".

Next, node may be limited based on content type in:
hook_access

The type of access names can be declared in:
hook_perm


To overwrite permission, you may edit hook_access within the same node module,
or use hook_nodeapi

stages:

• check for "access content"
• trigger nodeapi.op = "load"
  
• check for hook_access
• running "hook_view"
• trigger nodeapi.op = "view"
• ...

Please advice me if I've missed out or made any mistake here.