Mixing patterns with string patterns

Question

I have imported an XML document into Mathematica. It is now represented as Symbolic XML expression in the variable xml:

XMLObject["Document"][{XMLObject["Declaration"]["Version" -> "1.0"]}, 
 XMLElement[
  "slideshow", {}, {XMLElement["title", {}, {"XML Tutorial"}], 
   XMLElement[
    "slide", {}, {XMLElement["title", {}, {"Agenda"}], 
     XMLElement["item", {}, {"Introduction"}], 
     XMLElement["item", {}, {"XML technologies"}], 
     XMLElement["item", {}, {"Editors for XML documents"}]}]}], {}]

Using the Cases function I want to extract the XMLElement expressions whose plain text contents contain the word "XML":

Cases[xml, XMLElement["item", _, {___ ~~ "XML" ~~ ___}], Infinity]

This however returns the empty list, probably because it is mixing a Mathematica expression pattern with a string expression pattern. How does one go about embedding a string pattern into a regular pattern?

Answer 1

I'd have used StringMatchQ[] if I was in your shoes:

xmlDoc = XMLObject[
    "Document"][{XMLObject["Declaration"]["Version" -> "1.0"]}, 
   XMLElement[
    "slideshow", {}, {XMLElement["title", {}, {"XML Tutorial"}], 
     XMLElement[
      "slide", {}, {XMLElement["title", {}, {"Agenda"}], 
       XMLElement["item", {}, {"Introduction"}], 
       XMLElement["item", {}, {"XML technologies"}], 
       XMLElement["item", {}, {"Editors for XML documents"}]}]}], {}];

Cases[xmlDoc, XMLElement["item", _, {s_String /; 
    StringMatchQ[s, ___ ~~ "XML" ~~ ___]}], Infinity]

which yields

{XMLElement["item", {}, {"XML technologies"}], 
 XMLElement["item", {}, {"Editors for XML documents"}]}