NAS is a software suite that enables applications to be 
integrated across a distributed network of multivendor 
systems: NAS services are divided into four main groups:
 - Application Access Services which support user interface 
(forms based,graphical or character terminal based)
 - Communication and Central services which support 
communications using electronic mail and EDI
 - Information and resource sharing, which supports 
database access and compound documents (collection of 
images, graphics and conventional text)
 - System Access services which provides a standard 
operating system interface.