How to fix Eclipse validation error “No grammar constraints (DTD or XML schema) detected for the document.”?

Eclipse is throwing an XML schema warning message in all xml file: “No grammar constraints (DTD or XML schema) detected for the document.”

answer:

I am not an expert but a learner. I accidentally found an easy and stupid way to solve the problem. What you just need to do is:

Press ctrl + shift + F (it's a shortcut to format the file in Eclipse)

If this does not solve the problem then press the TAB key at the starting of this particular line
?xml version="1.0" encoding="UTF-8"? and not anywhere else (I don't not why, but this works. If anyone here knows why I will be very happy to know)

Then press ctrl + shift + F and save.

The warning will be gone, at least for me, you may try for yourself...

--Madhavi--

Source: http://stackoverflow.com/questions/4833057/how-to-fix-eclipse-validation-error-no-grammar-constraints-detected-for-the-doc