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Documentation/DimBased/dim.ptex

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+% BE SURE TO EDIT design.ptex
+\documentclass{article}
+
+\usepackage{rcs}
+\RCS $Date: 2000/03/04 15:45:59 $
+\RCS $Revision: 1.1 $
+\date{Rev.\RCSRevision~~\RCSDate}
+
+\title{Dimension-based thinking for ZigZag}
+\author{Tuomas J. Lukka}
+\begin{document}
+\maketitle
+
+\def\zz{ZigZag}
+
+\section{Introduction}
+
+When designing the code to implement a \zz\ space, the 
+place most people would start at would be the cell object, which would
+have a set of pointers to other cells, named with dimension names.
+However, this is not the only way to structure the internals - indeed,
+it is not necessarily a good way at all.
+
+\section{Dimension-based view}
+
+With cells, you have to always take steps to enforce the two-directional
+connection consistency rule.
+The dimension-based view starts from the realization that if we consider
+each {\em dimension} an entity by itself, this gets much simpler: 
+simply put, each dimension is a one-to-one mapping from some cells of the
+space to some other cells. 
+
+\section{Advantages}
+
+The dimension-based view has several advantages:
+\begin{itemize}
+\item {\bf Specialization}
+	It is much easier to define a single dimension object to 
+	do something different than the others, e.g. a dimension where
+	getting the {\it n}th cell is fast but inserting and deleting cells
+	is allowed to be slow.
+\item {\bf Simplicity}
+	Since one object is in charge of the both ends of a connection,
+	it is easier to avoid mistakes. Coding transient cell connections
+	is easy as well, as that object can keep tabs on the transient
+	connections separate from the stable ones.
+
+
+
+% .PS
+% box "Clang" ht 0.25
+% .PE
+% $$\box\graph$$