"in-scope" and BIND question

I havea a question on in-scope variables and BIND, particularly, on item 12. in
http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#sparqlGrammar

"
 *   The variable assigned in a BIND clause must not be already in-scope<http://www.w3.org/TR/sparql11-query/#variableScope>.
"

I am not sure here, what "already" in-scope means. Can we clarify that?
Particularly, when reading the in-scope definition, I am a bit unsure of what happens
with regards to e.g. UNION queries, i.e. my feeling is that

SELECT *
   {
    { BIND (1 AS ?Y) }
     UNION
    { <s> <p> ?Y }
  }

shouldn't be different from

SELECT *
 {
   { <s><p> ?Y }
    UNION
    { BIND (1 AS ?Y) }
 }

and both should be allowed (returning 1 on the empty graph), is that correct?

However, strictly reading:

thanks,
Axel


--
Dr. Axel Polleres
Siemens AG Österreich
Corporate Technology Central Eastern Europe Research & Technologies
CT T CEE

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