why export to XML?
The netflow protocol has its own format and (free) reporting tools for about any operating system available. Most decent router software suites have this as standard built-in. Call me silly, but the router device in your home or company is the true connection hub where all traffic goes through, making it the most efficient location to track any and all traffic on your network.
Reports can be exported to excel, HTML, csv. Functionality that is built into the reporting tools by default. Some of these reports allow you to export the content in whatever shape or form. And most router software and reporting tools have the option to take the content coming in through netflow and display it graphically, using time-lines, statistics and/or charts, practically in real-time, keep track of history etc.
Collecting and processing of netflow data can be done on the router itself or on a dedicated (virtual) server, if you so wish. The ISP I worked for had such software already installed on the NT4 windows box assigned to my care. That software was already so complete and capable, so is was also used to bill the customers of that ISP. That was still in the days where you had to pay for the amount of data you pushed/pulled to/from the Internet.
So I don't know what problem Nettraffix is trying to solve here, just by by using XML as export.