The Directory Service Interfaces
The X/Open Directory Service (XDS) and X/Open Object Management (XOM) application programming interfaces provided by the DCE Directory Service are based on X/Open specifications. APIs are not really separate components (every DCE component includes APIs to access it), but we call them out separately in this case because programmers use the Directory Service APIs to access both DCE directory services - CDS and GDS.
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The XOM Application Programming Interface
Additional Information on XDS and XOM