extract node names as column headers using XPath node?

Community Extensions
1

I've used the Palladian nodes to retrieve data from a web server, and parse the returned html to an xml column. All good.

Using the XPath node, I can extract the values from each node into separate columns in a table so long as the column header is specified in the New Column Name field (that is, a fixed value for all columns, followed by a number: COLUMNnnn).

But I can't work out how to extract the node names as column names.

My XPath Value query is //*
XPath query for column name: /name()
Xpath data type: String cell
Multiple tag options: Multiple columns

This gives in the summary section Column Name = Value of //*/name()

But on executing the (knime) node:

Error Xpath 2:23 Execute failed: Xpath expression cannot be compiled  

Instead of /name(), I have also tried /local-name(), /node-name().

Any pointers?

(the other)
Simon

2

Hi Simon the other,

I'm no expert on the XPath nodes, but I assume the problem is as follows (quoted from the node documentation): "The node supports XPath 1.0."

Queries such as "//*/name()" however are only supported in XPath 2.0 (see here).

Admittedly, I have no clue if there's any workaround.

Kind regards,
Philipp

3

Thanks Philipp. I figured that might be the case, but I couldn't work out how to construct a 1.0 compliant version from within the XPath node.

Perhaps I should look at the Selenium nodes and see if it's easier to parse the output from those nodes into separate columns?

(the other)
Simon

4

Hey Simon,

with the Selenium Nodes, you can check the option "Append additional WebElement information", which will give you a dedicated column with the extracted node names. You can use the same XPath query //* to get all elements on the page. However, the elements will be extracted row-wise (i.e. for each found element, a row is created). I guess it should be easy to transform that into a column-based table.

node description

Hope I understood your issue correctly. In case you have any improvement suggestions, feel free to get in touch (forum or email).

Best,
Philipp

5

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