Re: I am looking for references on updatable views
From: Mikito Harakiri <mikharakiri_nospaum_at_yahoo.com>
Date: 7 Oct 2005 14:28:28 -0700
Message-ID: <1128720508.894527.238030_at_z14g2000cwz.googlegroups.com>
Date: 7 Oct 2005 14:28:28 -0700
Message-ID: <1128720508.894527.238030_at_z14g2000cwz.googlegroups.com>
"Show me your view update strategy, and I'll prove it failing on my
example"
The example I have in mind is very simple. Consider
rename( X(t,v), v->w ) = Y(t,w)
If we update the view Y, what modification to the relation X data
should be? This might seem absurdly naive example, since the view
equation solves in a moment
X(t,v) = rename( Y(t,w), w->v )
Not so fast, however. Let <v=w> be (an infinite) binary relation
{(v,w) | v=w}. Then, the first view equation can be written as
project_t_w(X(t,v) join <v=w>) = Y(t,w)
Y is still a perfectly updateable view, but suddenly, the method of
solving this equation becomes not obvious.