ansaurus

Question

Xpath query and time

Answer 1

A:

If you generate the xml yourself, you could change the way you store the time attribute using an integer value (ticks, for example), then you could do an easy numerical comparison using something like

//sub[@time > 1389893892]

axel_c 2009-01-24 12:35:52

I don't generate it myself and they don't want to change the way it is generated...

2009-01-24 12:38:21

Answer 2

+1 A:

Well as long as the time is HH:MM something like the following should work: (I must excuse my syntax since I'm just dabbling without running, consider this pseudo-xpath):

xmlns:fn="http://www.w3.org/2005/02/xpath-functions"

//sub[fn:compare(@time,'12:59') > 0][1]/status

This should select all the elements where time is greater than 12:59 and then select the first of those elements.

You could also pass the value '12:59' as an external parameter into the xpath evaluation.

krosenvold 2009-01-24 12:36:37

This sounds really interesting, I must try. The exact link to the compare function is http://www.w3.org/TR/xpath-functions/#func-compare (very good explanation too)

2009-01-24 12:55:24

It is simpler to just use "lt" and "gt" when comparing two xs:time values.

Dimitre Novatchev 2009-01-24 16:57:00

Answer 3

+2 A:

Here is the ugly Xpath 1.0 solution:-

sub[number((substring-before(@time, ':')) * 60 + number(substring-after(@time, ':'))) &gt; 959][1]

Note 959 = 15 * 60 + 59 which I'm sure you can do in your calling code.

Give that node the previous node can be accessed as:-

preceding-sibling::sub[1]

However a pragmatic, common sense solution would be to load the XML data into a set of data structures and use a language more suited to this task to look the items up.

AnthonyWJones 2009-01-24 12:54:54

Well, someone created XPath to be good at querying XML files...

2009-01-24 13:00:56

For an XPath solution, that's the way to go. It's not even especially ugly, IMHO. +1

Tomalak 2009-01-24 13:02:35

I'll test this solution and the krosenvold one (this last sounds more interesting, expecially if it works) :-)

2009-01-24 13:06:04

@Tomalak: I must admit I was expecting it to be much uglier but you're right its not actually that bad.

AnthonyWJones 2009-01-24 14:06:09

No need to calculate the total seconds -- see my answer.

Dimitre Novatchev 2009-01-24 16:57:42

@AnthonyWJones: Anthony, is there a way to concat numbers as if they were strings? I could convert that 15:59 into 1559 and compare it with 1600.

2009-01-24 17:06:12

Answer 4

+2 A:

Here are two solutions:

I. XPath 1.0

This is one pair of XPath 1.0 expressions that select the required nodes:

/*/*
    [translate(@time, ':','') 
    > 
     translate('15:59',':','')
    ][1]

selects the first sub node with time later than 15:59.

/*/*
    [translate(@time, ':','') 
    < 
     translate('15:59',':','')
    ][last()]

selects selects the first sub node with the previous than 15:59 sub time.

We can include these in an XSLT transformation and check that the really wanted result is produced:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"&gt;
  <xsl:output omit-xml-declaration="yes"/>

    <xsl:template match="/">
      First time after 15:59: 
      <xsl:copy-of select=
       "/*/*
          [translate(@time, ':','') 
         > 
           translate('15:59',':','')
          ][1]
      "/>

      First time before 15:59: 
      <xsl:copy-of select=
       "/*/*
          [translate(@time, ':','') 
         &lt; 
           translate('15:59',':','')
          ][last()]
      "/>
  </xsl:template>
</xsl:stylesheet>

When the above transformation is applied on the originally provided XML document:

<mainNode>
    <sub time="08:00">
     <status id="2">On</status>
     <status id="3">Off</status>
    </sub>
    <sub time="13:00">
     <status id="4">On</status>
     <status id="7">On</status>
    </sub>
    <sub time="16:00">
     <status id="5">On</status>
     <status id="6">On</status>
     <status id="7">Off</status>
     <status id="8">On</status>
    </sub>
    <sub time="20:00">
     <status id="4">Off</status>
     <status id="7">On</status>
    </sub>
    <sub time="23:59">
     <status id="4">On</status>
     <status id="7">On</status>
    </sub>
</mainNode>

the wanted result is produced:

  First time after 15:59: 


<sub time="16:00">
     <status id="5">On</status>
     <status id="6">On</status>
     <status id="7">Off</status>
     <status id="8">On</status>
</sub>

  First time before 15:59: 

 <sub time="13:00">
     <status id="4">On</status>
     <status id="7">On</status>
 </sub>

Do note the following:

The use of the XPath translate() function to get rid of the colons
The use of the last() function in the second expression
There is no need to convert the time to seconds before the comparison
When used as part of an XML document (such as an XSLT stylesheet, the < operator must be escaped.

II. XPath 2.0

In XPath 2.0 we can use the following two expressions to produce select the desired nodes:

/*/*[xs:time(concat(@time,':00')) 
    gt 
     xs:time('15:59:00')
    ][1]

selects the first sub node with time later than 15:59.

/*/*[xs:time(concat(@time,':00')) 
   lt 
     xs:time('15:59:00')
    ][last()]

selects selects the first sub node with the previous than 15:59 sub time.

We can include these in an XSLT 2.0 transformation and check that the really wanted result is produced:

<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
    <xsl:output omit-xml-declaration="yes"/>

    <xsl:template match="/">
      First time after 15:59: 
      <xsl:copy-of select=
       "/*/*[xs:time(concat(@time,':00')) 
           gt 
             xs:time('15:59:00')
             ][1]
      "/>

      First time before 15:59: 
      <xsl:copy-of select=
       "/*/*[xs:time(concat(@time,':00')) 
           lt 
             xs:time('15:59:00')
          ][last()]
      "/>
    </xsl:template>
</xsl:stylesheet>

When the above transformation is applied on the originally provided XML document (the same as in the first solution), the same wanted result is produced.

Do note the following:

In XPath 2.0 xs:time is a native data type. However, in order to construct an xs:time() from the values in the xml document, we have to concat to them the missing seconds part.
In XPath 2.0 xs:time values can be compared with the "atomic-value comarison operators" such as lt or gt.

Dimitre Novatchev 2009-01-24 16:53:55

Hi Dimitre, why that 2 here? [translate(@time, ':','') > translate('15:59',':','') ][2]

2009-01-24 17:14:54

@vyger Thanks for pointing this -- some weird bug in the "code" button. The indexes in the XSLT 2 code were shown as 7 and 8. Just edited it, if this continues, I will edit further and will not use the code button.

Dimitre Novatchev 2009-01-24 18:18:29

Dmitre, your solutions were really complete, sorry for pointing out that typo. The first one is the solution I was looking for: I imagined it could be done but eventually I did not know how. Thanks! :-) Could you suggest a good book about XPath?

2009-01-24 18:30:44

@vyger See: http://tinyurl.com/dd4tsyThis is about XSLT books, but they cover by necessity XPath very well. My favourite is Michael Kay and his latest book on both XSLT 2.0 and XPath 2.0. BTW, if you think and answer is what you wanted, you can select it (click the check mark)

Dimitre Novatchev 2009-01-24 18:36:31

Checked, thanks for the suggestions :-)

2009-01-24 18:52:57

+1. Nice answer. Good to see you on SO as well ;)

AnthonyWJones 2009-01-24 21:00:16

Dimitre Novatchev 2009-01-24 21:53:52

ansaurus

tags:

views:

answers:

Xpath query and time

I. XPath 1.0

II. XPath 2.0

related questions