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DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES



PROGRAMMING LANGUAGES SEMINAR

                    -Thursday, April 20, 1989

Mr.  Scott  Vorthmann, of the School of Information and
Computer   Science   at   the   Georgia   Institute  of
Technology,   will  speak  on  "Syntax-Directed  Editor
Support for Incremental Consistency Maintenance."


TIME:        3:30 PM

ROOM:        DC 1302

ABSTRACT

The   technology   of  syntax-directed  editors  offers
characteristics which are ideally suited to the task of
incremental  consistency  maintenance.   In particular,
the   use  of  attribute  grammars  to  provide  static
semantic  analysis  has several specific advantages:  a
fine  granularity  of processing, a fine granularity of
dependencies  to  direct  that  processing,  caching of
derived  data,  and  algorithms  which update that data
with  a minimal amount of processing.  However, several
shortcomings  of  this  approach  have been identified.
The  described  research  addresses  these shortcomings
with  extensions  to  the technology of syntax-directed
editor generation.

The  principal  extension  is  the addition of a naming
layer  to  the  editor kernel architecture.  The naming
layer  supplements  the  tree structure provided by the
syntax with non-local references (from identifier usage
sites  to  declaration  sites),  presenting a directed-
graph  as  the  structure  now underlying the attribute
propagation.   Naturally,  the  naming  layer  must map
certain    syntactic   modifications   to   appropriate
adjustments  to  this binding graph, and must produce a
unique state of the binding graph for a given syntactic
state.

The  behaviour  of the naming layer with respect to the
syntactic  and attribute grammar layers is specified by
a  Naming Specification Language, which is simply a set
of   extensions   to   an  existing  attribute  grammar
notation.    NSL   supports  the  designation  of  name
declaration  and  reference  sites,  the designation of
productions  that  embody  scopes, and specification of
visibility   of  names  between  related  scopes.   The
visibility  mechanisms  provided  by  NSL  are its most
important features.