Found a mistake in the Schematron of DocBook 5.1b7

[Hussein Shafie <hussein@xmlmind.com>]

In some cases, the logic of s:assert is inverted:

---
<s:pattern>
  <s:title>XLink locator placement</s:title>
  <s:rule context="*[@xlink:type='locator']">
     <s:assert test="not(parent::*[@xlink:type='extended'])">An XLink 
locator type element must occur as the direct child of an XLink extended 
type element.</s:assert>
  </s:rule>
</s:pattern>

<s:pattern>
  <s:title>XLink resource placement</s:title>
  <s:rule context="*[@xlink:type='resource']">
     <s:assert test="not(parent::*[@xlink:type='extended'])">An XLink 
resource type element must occur as the direct child of an XLink 
extended type element.</s:assert>
  </s:rule>
</s:pattern>

<s:pattern>
  <s:title>XLink title placement</s:title>
  <s:rule context="*[@xlink:type='title']">
     <s:assert test="not(parent::*[@xlink:type='extended']) and 
not(parent::*[@xlink:type='locator']) and 
not(parent::*[@xlink:type='arc'])">An XLink title type element must 
occur as the direct child of an XLink extended, locator, or arc type 
element.</s:assert>
  </s:rule>
</s:pattern>
---

should read:

---
<s:pattern>
  <s:title>XLink locator placement</s:title>
  <s:rule context="*[@xlink:type='locator']">
     <s:assert test="parent::*[@xlink:type='extended']">An XLink 
locator type element must occur as the direct child of an XLink extended 
type element.</s:assert>
  </s:rule>
</s:pattern>

<s:pattern>
  <s:title>XLink resource placement</s:title>
  <s:rule context="*[@xlink:type='resource']">
     <s:assert test="parent::*[@xlink:type='extended']">An XLink 
resource type element must occur as the direct child of an XLink 
extended type element.</s:assert>
  </s:rule>
</s:pattern>

<s:pattern>
  <s:title>XLink title placement</s:title>
  <s:rule context="*[@xlink:type='title']">
     <s:assert test="parent::*[@xlink:type='extended'] or 
parent::*[@xlink:type='locator'] or parent::*[@xlink:type='arc']">An 
XLink title type element must occur as the direct child of an XLink 
extended, locator, or arc type element.</s:assert>
  </s:rule>
</s:pattern>
---

The above mistake  is found in both docbook.sch and assembly.sch (didn't 
look at the other .sch files).