 WIDTH="2em" VALIGN="top">-</TD>
        <TD>A model of one of the <A HREF="../guide/concepts.html#filter_concepts">Filter</A> concepts</TD>
    </TR>
    <TR>
        <TD VALIGN="top"><I>Device</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
        <TD>A <A HREF="../concepts/blocking.html">Blocking</A> <A HREF="../concepts/device.html">Device</A> whose <A HREF="../guide/modes.html">mode</A> refines that of <CODE>T</CODE>.</TD>
    </TR>
</TABLE>

<H4>Semantics</H4>

<PRE CLASS="broken_ie"><SPAN CLASS="keyword