On Tue, 2023-01-17 at 20:09 +0000, Roger L Costello costello@xxxxxxxxx
wrote:
>
> I want an XPath expression that returns a sequence of (Target-
> Latitude, Target-Longitude) pairs; i.e., a pair for each
> <Observation> element. For the XML document shown above, the XPath
> should return this sequence:
>
> (10,20), (15,25)
>
> A count of the number of items in the sequence should yield: 2

As others have said, you can't do this in the XPath Data Model with
sequences, but you can with arrays of course.

let $input := <Track-History>
    <Track-ID>XYZ</Track-ID>
    <Observation>
        <Target-Latitude>10</Target-Latitude>
        <Target-Longitude>20</Target-Longitude>
        <Observer-Latitude>40</Observer-Latitude>
        <Observer-Longitude>50</Observer-Longitude>
    </Observation>
    <Observation>
        <Target-Latitude>15</Target-Latitude>
        <Target-Longitude>25</Target-Longitude>
        <Observer-Latitude>40</Observer-Latitude>
        <Observer-Longitude>50</Observer-Longitude>
    </Observation>
</Track-History>
return for $observation in $input/Observation
return [
  xs:integer($observation/Target-Latitude),
  xs:integer($observation/Target-Longitude)
]

If you wrap that whole thing in count( ... ) you get 2.

You possibly want xs:double() rather than xs:integer(), or xs:string(),
in production of course.

liam

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