Question

Is it possible to integrate a real (not encoded in characters) binary block (best with defined byte-order and word-length) into an XML file?

Answer 1

No, it is not possible while keeping within the xml standard.

The allowable set of characters in a parsed XML entity is tab, carriage return, linefeed, and valid unicode characters. There are various bytes that fall outside of this allowable range, most prominently 0x0, but also 0x1 – 0x8, 0xB – 0xC, and 0xE – 0x1F (i.e., most values that are classically ASCII control characters).

You can’t even include them as numeric entities, since they aren’t valid characters. i.e., the following will not validate:

<test>
    Testing ^A: &#x1;
</test>

See http://www.w3.org/TR/2006/REC-xml11-20060816/#charsets