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Most modern databases have XML functions that can be used to extract data in an XML format. I want to avoid the task of manually calling XML functions to extract the data.

This problem involves devising a generic solution to create XML documents based on mapping database tables (and JOIN conditions) to XPath expressions.


An XPath map codifies associations between an XML document and relational data as follows:

root               > people              -- "root" is a special keyword
person             > person              -- > is a node to table relation
person.first_name -> name/first          -- -> is a node/attribute to column relation
person.last_name  -> name/last
person.age        -> [@age]
account.person_id => person.person_id    -- => is a join
account            > person/account
account.number    -> [@id]

Where a PERSON table might resemble:

person_id | first_name | last_name | age
      123 | Peter      | Parker    | 18
      456 | James      | Jameson   | 42

Where an ACCOUNT table might resemble:

account_id | person_id | number
         1 |       123 | 123456789

Calling a function using the XPath map would produce the following XML document:

  <person age="18">
    <account id="123456789" />
  <person age="42">

In this case, James Jameson does not have an account and so the corresponding XML element (account) is not included in the final document.

This is a difficult problem and a complete solution is not necessary. A solution that handles 80% of simple tables mapped to simple XML elements and attributes would suffice.


What algorithm would return an XML document based on such a generic XPath map? The algorithm must transform the structure defined by the XPath map into an XML document with the content from the relations defined in the XPath map.

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closed as too broad by Jack Douglas Feb 5 '15 at 11:06

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

This reads more like a project than a question. – Mark Storey-Smith Apr 8 '13 at 16:56
A canonical answer cannot be provided as the implementation would differ between RDBMSs. Polling for existing solutions is off-topic. Nothing has been presented to demonstrate what you've tried so far. Please edit the question to narrow the scope of what you're asking. As it sits, I would vote to close, but can't because of the bounty. – Jon Seigel Apr 8 '13 at 18:46
SQL server is a RDBMS that has built in XML functions, and it pretty much follows the XPath standard defined by the World Wide Web Consortium. – StanleyJohns Apr 8 '13 at 20:31
I've never heard of "Xpath map" before. Is that something you just invented? – Trygve Laugstøl Apr 15 '13 at 6:38