<h2> Entity representations and implementations
<node> mm-backend
<p>
-Entity \e$B$OCj>]2=$5$l$?%G!<%?I=8=$G!"<B:]$N%G!<%?I=8=$H$7$F$OMQES$K1~$8$F\e(B
-\e$B$5$^$6$^$J$b$N$,MxMQ$G$-$k$h$&$K@_7W$5$l$F$$$^$9!#\e(B
+Entity is an abstraction. It is designed to use various data
+representations for their purposes.
<p>
-\e$B$3$3$G!"\e(Bentity \e$B$,$I$&$$$&<oN`$NI=8=$r9T$C$F$$$k$+$r<($9$N$,\e(B
-<concept>representation-type</concept> \e$B$G!"\e(Bentity \e$B$r@8@.$9$k;~$K$O$3$l$r\e(B
-\e$B;XDj$7$^$9!#\e(B<cf node="Entity Creation">
+Each entity has <concept>representation-type</concept>. It must be
+specified when an entity is created. <cf node="Entity Creation">
<p>
\e$BA0@a$^$G$K=R$Y$FMh$?\e(B entity \e$B$KBP$9$k=hM}$O!"\e(Bentity \e$B$KBP$7$F$=$N=hM}$r0M\e(B
\e$BMj$9$k$3$H$K$h$C$F<B8=$5$l$F$$$^$9!#\e(BEntity \e$B$O<+J,$N\e(B