diff --git a/APCCM2017_Stanger.tex b/APCCM2017_Stanger.tex index c53ebb8..5b06721 100644 --- a/APCCM2017_Stanger.tex +++ b/APCCM2017_Stanger.tex @@ -1139,9 +1139,7 @@ \section{Conclusion \& future work} \label{sec-conclusion} -% shows promise as a means of formally characterising and modelling Date's notion of information equivalence, and thus validating his approach - -\noindent In this paper we have shown how to use the concept of relative information capacity and an extension of the schema intension graph (SIG) formalism to more formally model Date's notion of information equivalence with respect to relational view updates. Our analysis of Date's restriction view example \cite{Date.C-2013a-View} using these techniques is consistent with his findings. The information capacities of \(\SC{1} = \{S\}\) and \(\SC{2} = \{\LS,\NLS\}\) are equivalent, so it should be possible to effectively propagate view updates between \(\SC{1}\) and \(\SC{2}\), regardless of the configuration of views and base relvars. Conversely, the information capacity of \(\SC{3} = \{\LS\}\) is not comparable with that of \(\SC{1}\), implying that there are updates that cannot be propagated between \(\SC{1}\) and \(\SC{3}\). +\noindent In this paper we have shown how to use the concept of relative information capacity and an extension of the schema intension graph (SIG) formalism to more formally model Date's notion of information equivalence with respect to relational view updates. Our analysis of Date's restriction view example \cite{Date.C-2013a-View} using these techniques is consistent with his findings, so the approach shows promise. The information capacities of \(\SC{1} = \{S\}\) and \(\SC{2} = \{\LS,\NLS\}\) are equivalent, so it should be possible to effectively propagate view updates between \(\SC{1}\) and \(\SC{2}\), regardless of the configuration of views and base relvars. Conversely, the information capacity of \(\SC{3} = \{\LS\}\) is not comparable with that of \(\SC{1}\), implying that there are updates that cannot be propagated between \(\SC{1}\) and \(\SC{3}\). Our analysis shows the importance of clearly identifying all explicit and implicit constraints that can be propagated from the base schema \(\SC{0}\) to its sub-schemas. Omission of constraints could lead to a different SIG structure that might not be comparable, or might lead to an erroneous conclusion about a schema's information capacity relative to another.