You are seeing a modest XML document from MT's own site, which started out as XHTML plus some extraneous material.
The pipeline you ran this through to get here (showcase/V2S) is a pipeline which validates its input twice, forgiving errors the first time, throwing away any elements that weren't recognised, and trying again, reporting errors this time. This strategy often is what is wanted if you have an document for a new version of a schema, but not the schema, and you'd like to process it as if it were just what the old schema allowed.
This pipeline exploits the power of Markup's pipeline engine, which connects operations with a high-efficiency infoset bus, and caches schemas, stylesheets and other static resources. You can see the pipeline description which was compiled to produce this pipeline for the server to run.
Please note that this is not a schema development tool -- if your schema document is invalid, or doesn't correspond to a valid schema, you won't get much in the way of error messages - use XSV online to debug your schemas.
If you look at this document in the raw, you will see that it has non-XHTML elements at the end, which have been stripped out by the pipeline.
It's probably easier to use the form for this pipeline, but if you want to construct a URL to use your own schema document (and you must specify one -- the
schema caching mechanism does not look ahead to find
xsi:schemaLocation hints) on your own data, replace http://www.markup.co.uk:8888/yourinstance.xml
in the URL you're fetching with a full
URL (http: or https:) for the XML page you want to validate
and replace http://www.markup.co.uk:8888/xhtml1-strict.xsd
in the URL you're fetching with a full
URL (http: or https:) for a schema document corresponding to the schema you
want to validate with, and try again.