Question about Illustrator APIs

As others have noted, the .ai file format is proprietary and nasty, and the AI licensing terms do not allow running it on a public-facing server.

A further concern: it sounds like you’re reinventing InCopy.

https://www.adobe.com/products/incopy.html

If you can share some details of your product, perhaps we can offer more useful advice.

Well as already mentioned if the task is to convert ai document into XML without using the Illustrator app, then the task is very difficult because the format is proprietary. However, if you intend to use Illustrator for this task then you would be better suited to use the scripting SDK and you should be able to achieve much of what you want, for cases that you are not able to handle you can go the C++ plugin route as mentioned by @Rick E Johnson.

Another thing to keep in mind is that if the product is envisoned to be an automated solution where an ai document upload to a website etc would trigger the converion to XML automatically then I think you would be in violation of the terms of subscription. InDesign surely does not allow this type of automation and requires one to buy InDesign Server. So please clarify this point as well before commiting to the solution.

-Manan

Reading an Illustrator document is quite difficult. There are no public
APIs for doing so available from Adobe. Three is a free library that can do
it, but does not support versions newer than nearly twenty years ago. They
was a proprietary library that could do the job about fifteen years ago but
I don't know if it still exists, and even if it does, it was very
exprensive ($25k/year).

Bottom line is that using the Illustrator format as a payload is very
dicey, maybe not even possible.

Are you intending to parse the AI document without running Adobe Illustrator? You can use c++ in a plugin or JavaScript to communicate with Illustrator whle that file is open, but I know of no way to use it, say, a PHP environment.