I have simple document:<svg xmlns="http://www.w3.org/2000/svg">
<a>aadsf</a> </svg>

so the element there has name local name a in the namespace
http://www.w3.org/2000/svg

And now "//a" doesn't find a node

That selects elements with local name a in no namespace.
 

> I must use //*[local-name() ='a'],

That is possibly inefficient and selects any element with that local
name, a more usual approach is to say

 I must use //svg:a where your stylesheet has
 xmlns:svg="http://www.w3.org/2000/svg"

David

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