Open Systems Interconnection 
Open System Interconnection 
Open Systems Interconnect 
Office of Special Investigations 
Open Source Initiative 
Open System Interconnect 
Office of Systems Integration 
Open System Interface 
Operating Space Items 
Office of Special Investigation 
On Site Inspection 
Open Society Institute 
Ocular Scanning Instrumentation 
Office of Scientific Integrity 
Office of Scientific Intelligence 
Office of Strategic Information 
Online Service Information 
On-Site Inspection 
Open Standards Interconnection 
Open Switching Interval 
operational subsystem interface 
Objective Systems Integration 
Objective Systems Integrators 
Occupational Stress Indicator 
Ocean Security Initiative 
Office of Scientific Information 
Office of Scientific Investigation 
office of security inquires 
Office of Strategic Influence 
Office of Systems Integrations