$ xmllint --xpath "/*[ name() = 'alto' ] /*[ name() = 'Description' ] /*[ name() = 'MeasurementUnit' ]" alto.xml
<MeasurementUnit>inch1200</MeasurementUnit>

##</code><code>##

/*

# posy
/alto[1]

# star
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]

# rats
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]
 


# "content"
     inch1200 

------
/*/*

# posy
/alto[1]/Description[1]

# star
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]
/*[ name() = "Description" and position() = 1 ]

# rats
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]
 /Description[1]
 


# "content"
     inch1200 

------
/*/*/*

# posy
/alto[1]/Description[1]/MeasurementUnit[1]

# star
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]
/*[ name() = "Description" and position() = 1 ]
/*[ name() = "MeasurementUnit" and position() = 1 ]

# rats
/*[ name() = "alto" and position() = 1 and @xsi:schemaLocation = "http://www.loc.gov/standards/alto alto-v2.0.xsd" and @xmlns = "http://www.loc.gov/standards/alto/ns-v2#" and @xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" ]
 /Description[1]
 /MeasurementUnit[1]
 


# "content"
    inch1200

------