(Extracted, with permission, from the DCE FAQ, available at
http://www.osf.org/dce/faq-mauney.html)

DCE is the Distributed Computing Environment, from the Open Software
Foundation. (It is called "the DCE" by sticklers for grammatical
consistency.)

DCE consists of multiple components which have been integrated to work
closely together.  They are the Remote Procedure Call (RPC), the Cell
and Global Directory Services (CDS and GDS), the Security Service, DCE
Threads, Distributed Time Service (DTS),and Distributed File Service
(DFS).  The Threads, RPC, CDS, Security, and DTS components are
commonly referred to as the "secure core" and are the required
components of any DCE installation.  DFS is an optional component.

DCE is called "middleware" or "enabling technology."  It is not
intended to exist alone, but instead should be integrated or bundled
into a vendor's operating system offering.  DCE's security and
distributed filesystem, for example, can completely replace their
current, non-network, analogs.