Can somebody explain what is the difference between sxpath and txpath?
At the first view txpath is standart textual XPath representation, and sxpath is s-expressions based XPath query (or mixed XPath query). But I have confused that the following code is valid:
(write ((sxpath "/a/*/../*") doc))(newline)
(write ((txpath "/a/*/../*") doc))(newline)

(In DDO the diiference is explained by the samples
(ddo:txpath "table/tr[3]/td/@align") and
(ddo:sxpath '(table (tr 3) td @ align)) from http://modis.ispras.ru/Lizorkin/ddo.html\)

So, is the difference between sxpath and txpath included in the external presentation of the XPath query, or in some aspects of  implementation and functionality?

Another aspect that is not fully explained in SXPAth articles is how XPath query that contains complicated predicate can be written in s-expression based presentation? For example, such query: child::a[contains(string(child::*[last()]), "abc")] .