xml xmlns namespace and xsi_type extractions from xml using bash

Greetings.
I need to know how to pull the values from XML header information:

<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet href="http://www.accessdata.fda.gov/spl/stylesheet/spl.xsl" type="text/xsl"?>
<document xmlns="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hl7-org:v3 http://www.accessdata.fda.gov/spl/schema/spl.xsd">

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In addition, in several areas I have tags with xsi_type: attributes in it.  They do not show up in XPATH locations.  (ie. <tag xsi_type="CE" ... />

I am obligated to pull the xmlns, xmlns:xsi, xsi:schemaLocation and the specific tag (assuming I know the xpath to the tag) into a bash variable to do something with it.  Is this possible?

Thanks.

<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet href="http://www.accessdata.fda.gov/spl/stylesheet/spl.xsl" type="text/xsl"?>
<document xmlns="urn:hl7-org:v3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hl7-org:v3 http://www.accessdata.fda.gov/spl/schema/spl.xsd">
   

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