The Clinical Decision Support Implementer's Workbook, published in 2004 by the
Healthcare Information and Management Systems Society (HIMSS), is an
excellent introduction to this topic.

  I think that the term "decision support" is somewhat ill-fitting as it does not
adequately describe what the software is doing vis-a-vis the user.  That is to say,
CDS applications often serve to call to the attention of the user that an action is
needed, thus preventing errors of omission.  In that situation, the user is not in the
process of making a "decision".  As Robert Wears and Marc Berg put it in an
editorial in JAMA, "in many situations [in health care] “decisions” become
apparent only in retrospect" (JAMA 293:1261, 2005). 

 I think the term "knowledge delivery" (KD) more accurately describes what
these software functions attempt to achieve, though KD encompasses more than
what is usually considered to be automated CDS.  Click HERE for a diagram
outlining what I would propose as a functional model for KD and where CDS
fits in to that.