In a profile I can see:
<fieldPermissions>
<editable>true</editable>
<field>Time_Log__c.Date__c</field>
<readable>true</readable>
</fieldPermissions>
but using the 'Set Field-Level Security' web interface I can only see: visible and 'Read Only' options. Please, tell me what means readable? I suspect it means readable = Read Only + Visible
am I right?
Hidden
would indicate both flags are false.