if $set1 is a your sequence of books and $set2 is your sequence of Music
then you seem to want

$set1[concat(Author,'#',Country)=$m/concat(Author,'#',Country) ]

assuming # doesn't appear in Author or Country names.

David


On Thu, 21 May 2020 at 15:16, Roger L Costello costello@xxxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> Hi Folks,
>
> I have a set of Book instances. I call this Set #1. Here are two instances:
>
> <Book>
>     <Title>ABC</Title>
>     <Author>John Doe</Author>
>     <Country>USA</Country>
>     <Binding>hardcover</Binding>
> </Book>
>
> <Book>
>     <Title>XYZ</Title>
>     <Author>Mary Sue</Author>
>     <Country>CAN</Country>
>     <Binding>hardcover</Binding>
> </Book>
>
> I have a set of Music instances. I call this Set #2. Here is one instance:
>
> <Music>
>     <Genre>Classical</Genre>
>     <Author>John Doe</Author>
>     <Country>USA</Country>
>     <Cost>9.95</Cost>
> </Music>
>
> Query: Find the subset of Set #1 that intersects with Set #2 at the
> <Author> and <Country> elements.
>
> If Set #1 consists of the two instances shown above and Set #2 consists of
> the one instance shown above, then the result of the query is the following:
>
> <Book>
>     <Title>ABC</Title>
>     <Author>John Doe</Author>
>     <Country>USA</Country>
>     <Binding>hardcover</Binding>
> </Book>
>
> That Book instance has an <Author> and <Country> that intersects with the
> <Author> and <Country> in the Music instance.
>
> I view this as an intersection problem. However, it is an intersection at
> specific fields (the Author and Country fields). Do you view it as an
> intersection problem?
>
> If it is viewed as an intersection problem, then is there a nice XPath
> expression that does intersection-at-specific-fields?
>
> If it is better viewed not as an intersection problem, then how is it
> better viewed? is there a nice XPath expression for that view?
>
> /Roger