Question: Imagine I have data describing something, i.e. a person

```
Name Ander
Id  123123
tel 1313333333
some_other_unusual_id 1212

```

And I store it in a XML. The structure of the data (4 fields, those ones specifically) is unique and my company only uses it, but the data itself its stored in something common, such as XML. Can this structure be "private", under a license or patented? 

If someone get his hands in an example, can they write a `Ander_data_XML_read()` function in a programming language and release that function under GPL/BSD/MIT license?

Answer: 
This kind of thing was previously considered patent eligible (and some examples were found to be novel and non-obvious and granted patents) but they aren't considered patent eligible any longer.

A somewhat well known patent 6,128,415 of Polaroid's - "Device profiles for use in a digital image processing system", that covers a data structure for a profile in a digital camera. It was struck down a few years ago. The first issue now is not novelty or obviousness, but patent eligible subject matter, regardless of how inventive it might be. The PatentlyO blog had an article about this called [Data Structure Patent Ineligible](https://patentlyo.com/patent/2014/07/structure-patent-ineligible.html).
I am not a lawyer, but my opinion is that the data structure, as you describe it, would not be patentable. One requirement of a patent is inventiveness. I can see nothing inventive about storing data in a common data storage format. I suppose if you use the data or storage format in some unexpected way and gain an unexpected advantage, there might be a patentable aspect, but this is not suggested in your question. 

Historically software companies such as Microsoft, who wanted to protect their file formats used undisclosed binary files which were difficult to reverse engineer. This coupled with subtle changes to the formats with new versions of the software made file compatibility for competitors difficult. Another potential avenue to format protection might be copyright, but that is beyond my expertise and the scope of this site.