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                 Faulty Human Communications:
     Its Impact on Dependability And What To Do About It

                        John C. Knight

                Department of Computer Science
                    University of Virginia
                     Charlottesville, VA

In systems requiring ultra-high dependability, the  majority
of  software  defects that are found during testing or after
deployment are the result of requirements errors.  Of  those
requirements  errors,  a significant number occur because of
misunderstandings  about  the  system  context.    Essential
details  of  the  application  domain  are either unknown or
misunderstood by developers because of poor communication of
application domain knowledge.

Current software development practices focus on  the  formal
aspects   of   software.   While  formalisms  are  the  only
structures  required  to   communicate   with   a   machine,
contextual   information   is  required  for  developers  to
communicate  with  one  another   and   establish   software
validity.

The  pervasive  medium  for  this   communication,   natural
language, is understood to be problematic for high-precision
communication because of its  characteristic  ambiguity  and
informality.   However,  natural  language possesses its own
body  of  research  results  and  is  amenable  to  rigorous
inspection.    We   have   analyzed   the  domain  knowledge
communication problem as it arises in  software  engineering
from the perspective of current cognitive linguistic theory,
and this analysis has yielded a model that helps to  explain
sources  of  ambiguity  and  other  problems with the use of
natural language.  Using this model we have developed a  new
artifact  that  combines  software  function  and  essential
context information in a rigorous entity that we refer to as
a situated formalism.

In this presentation, I  briefly  summarize  the  linguistic
model   and   insights  derived  from  it,  e.g.,  that  the
considered use  of  natural  language  performs  a  function
unachievable  by  formal  means.   I  will explain how these
insights are exploited to  motivate  the  structure  of  the
situated  formalism  and  discuss  a  preliminary  practical
representation.  Finally, I will present some details of our
applications of the concepts discussed.


                            JOHN KNIGHT

John Knight is a professor of computer science at the  University
of  Virginia.  He  holds  a  B.Sc. (Hons) in Mathematics from the
Imperial College of Science and Technology (London) and  a  Ph.D.
in  Computer  Science from the University of Newcastle upon Tyne.
Prior to joining the University of Virginia in 1981, he was  with
NASA's Langley Research Center.

Dr. Knight's research interests are in software dependability. He
is  currently  working  on  projects  in safety-critical embedded
systems and the survivability of critical networked applications.
Specific  research  topics include the use of natural language in
specification,  tool  support  for  comprehensive   specification
development   and   analysis,   formal   verification,  assurance
arguments, and network survivability architectures.

 From 2001 to 2005 Dr. Knight served as Editor  in  Chief  of  the
IEEE  Transactions on Software Engineering, he is a member of the
editorial board of the Empirical  Software  Engineering  Journal,
and  he is the General Chair of the 2007 International Conference
on Software Engineering.