Avoid parentheses in path using XPath 1.0

Question

The following XML structure represents a website with many articles. Every article contains, among many other things, date of its creation and possibly arbitrarily many dates of its modification. I want to get the date of the last access (either creation or last modification) to every article using XPath 1.0.

<website>
    <article>
        <date><strong>22.11.2017</strong></date>
        <edits>
            <edit><strong>17.12.2017</strong></edit>
        </edits>
    </article>
    <article>
        <date><strong>17.4.2016</strong></date>
        <edits></edits>
    </article>
    <article>
        <date><strong>3.5.2011</strong></date>
        <edits>
            <edit><strong>4.5.2011</strong></edit>
            <edit><strong>12.8.2012</strong></edit>
        </edits>
    </article>
    <article>
        <date><strong>12.2.2009</strong></date>
        <edits></edits>
    </article>
    <article>
        <date><strong>23.11.1987</strong></date>
        <edits>
            <edit><strong>3.4.2001</strong></edit>
            <edit><strong>11.5.2006</strong></edit>
            <edit><strong>13.9.2012</strong></edit>
        </edits>
    </article>
</website>

In other words, the expected output is:

<strong>17.12.2017</strong>
<strong>17.4.2016</strong>
<strong>12.8.2012</strong>
<strong>12.2.2009</strong>
<strong>13.9.2012</strong>

So far I've only created this path:

//article/*[self::date or self::edits/edit][last()]

that looks for date and nonempty edits nodes in every article and selects the latter one. But I don't know how to access the latest strong of every such selection and the naive //strong[last()] appended to the end of the path doesn't work.

I found a solution in XPath 2.0. Either of these paths should work, if I'm not mistaken:

//article/(*[self::date or self::edits/edit][last()]//strong)[last()]
//article/(*//strong)[last()]

Such use of parentheses within path is invalid in XPath 1.0 though.

Alejandro · Accepted Answer · 2019-04-03 19:41:44Z

1

This XPath 1.0 expression

/website/article/descendant::strong[parent::date|parent::edit][last()]

Selects the nodes:

<strong>17.12.2017</strong>

<strong>17.4.2016</strong>

<strong>12.8.2012</strong>

<strong>12.2.2009</strong>

<strong>13.9.2012</strong>

Tested in http://www.xpathtester.com/xpath/56d8f7bc4b9c8c064fdad16f22469026

Do note: position predicates acts over the context list.

answered Apr 3, 2019 at 19:41

Alejandro

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2 Comments

Jeyekomon Over a year ago

Very clever! Thank you. By the way, I always expected the abbreviated syntax to give the same results as the full one, yet now I realized that the path /website/article//strong[parent::date|parent::edit][last()] selects completely different nodes.

Alejandro Over a year ago

@Jeyekomon You are welcome. The abbreviated syntax will be expanded to /child::website/child::article/descendant-or-self::node()/child::strong[position()=last()] so, here position() refers to the child axe.

supputuri · Accepted Answer · 2019-04-03 22:18:26Z

1

Here is the simple xpath to get your output.

//article/descendant-or-self::strong[last()]

answered Apr 3, 2019 at 22:18

supputuri

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2 Comments

supputuri Over a year ago

Curious to know, if this solves the issue. Though I checked from end, just want to check with you as you might have the entire structure.

Jeyekomon Over a year ago

Also correct answer. You're using the same trick as Alejandro with the unabbreviated syntax which did not come to my mind. I was stuck to only abbreviated one which was clearly faulty and probably unsolvable that way. Alejandro's solution is a bit safer though because he included the test for parents. The strong node can be relatively frequent within the article.

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