--- a/relpipe-data/specification.xml	Thu Jan 10 01:47:57 2019 +0100
+++ b/relpipe-data/specification.xml	Fri Jan 11 18:09:50 2019 +0100
@@ -110,6 +110,25 @@
 			If executed with STDIN attached to a file or another command (in a pipe), it reads data from this stream.
 		</p>
 		
+		<h3>relpipe-in-xml</h3>
+		
+		<p>
+			A tool that reads XML data in the format generated by <code>relpipe-out-xml</code>
+			and converts it back to the relational format.
+			Can be used together with XSLT procesor XQuery engine or other XML generator in two basic scenarios:
+		</p>
+				
+		<ul>
+			<li>as an input filter: to convert other formats to relational data</li>
+			<li>as a transformation: in pipeline: <code>relpipe-out-xml | some-xml-processor | relpipe-in-xml</code></li>
+		</ul>
+		
+		<p>
+			XQuery is very powerful language that can do various transformations, filtering and even JOIN and UNION operations.
+			So its power is comparable to relational databases.
+			In future <m:name/> releases, there will be also an SQL transformation tool, where these operations will be defined in classic SQL syntax.
+		</p>
+		
 		<h3>relpipe-out-tabular</h3>
 		
 		<p>