limited to the information that <i>W</i> directly observes.
</p>

<p>
The <i>happens before</i> relation is defined as the transitive closure of the
union of the sequenced before and synchronized before relations.
</p>

<p>
<b>Requirement 3</b>:
For an ordinary (non-synchronizing) data read <i>r</i> on a memory location <i>x</i>,
<i>W</i>(<i>r</i>) must be a write <i>w</i> that is <i>visible</i> to <i>r</i>,

For instance, this example:
</p>

<pre>
	goto L  // BAD
	v := 3
L:
</pre>

<p>
is erroneous because the jump to label <code>L</code> skips
the creation of <code>v</code>.
</p>

<p>
A "goto" statement outside a <a href="#Blocks">block</a> cannot jump to a label inside that block.
For instance, this example:
</p>

<pre>
if n%2 == 1 {

For instance, this example:
</p>

<pre>
	goto L  // BAD
	v := 3
L:
</pre>

<p>
is erroneous because the jump to label <code>L</code> skips
the creation of <code>v</code>.
</p>

<p>
A "goto" statement outside a <a href="#Blocks">block</a> cannot jump to a label inside that block.
For instance, this example:
</p>

<pre>
if n%2 == 1 {