Difference between using current node (.) and text() function in XPath for Selenium locators

Recently someone asked about using the partial link text to find an anchor with an IMG tag in the middle of the text. The HTML snippet was:

<a href="something.html">
&nbsp;
<img src="filename.gif">
&nbsp;
partial link text
</a>

The initial attempt for a locator was:

"//a[contains(text(),'partial link text')]"

Normally I would expect this to work. However, the text() function does not seem to find it. Peter Jeffery Gale (thanks Peter) noticed that the following locator did work:

"//a[contains(.,'partial link text')]"

The . notation is the current node in the DOM. This is going to be an object of type Node. I'm guessing that the Node is getting cast to a string. Something similar to:

"//a[contains(string(.),'partial link text')]"

The end result seems to be that getting the entire Node, convert it to a string and scanning the string for a substring always works. Using the XPath function text() to get the text for an element only gets the text up to the first inner element. If the text you are looking for is after the inner element you must use the current node to search for the string and not the XPath text() function.