d rules have direction forward.</p>
<p style="border-style: initial; border-color: initial;">Assertions with direction code are not used in normal inference at all; instead, special HL modules have been written to supplant the need for inference using the assertion itself, and the assertion remains in the KB for documentation purposes only. Code assertions cannot be edited via the HTML interface.</p>
<p style="border-style: initial; border-color: initial;">One way of viewing directions is as a hierarchy of 