- PDF data sheet.
- Spectral data.
- 3D model (a simplified 3D model is ideal for Revit applications).
Now I think examples are easier to understand than formal definitions, so here is what the start of an OXL file looks like:
Because Eulumdat and IESNA files are so constricted, some companies "expand and re-interpret" them, with non standard "extensions" which only a few programs (mostly company internal programs) understand. These extensions often force more data into the lines than they were designed for.
Eulumdata LDT has another restriction, it is only for CG (internal and road) photometries, and cannot hold VH (external floodlight) photometries.
OXL on the other hand is flexible and future proof. Since it is an XML format your programs/programmers/personel can ignore the branches it doesn't need and only pick out the data it wants. Also you can add your own special data which may be useful to your company, but can safely be ignored by extermal lighting programs.
Here is a link to an OXL photometric file which contains a photo and a spectrum.
Here is a link to 10 example OXL files in a single zip.
Here is the OxyTech web page which explains more about the OXL file format and here is a link to a (rather dated) OXL presentation.
But above all you should remember this image which illustrates what an OXL file can contain: