As far as i know, & and < are special characters for xml. so we need to escape those two characters to make the string be well-formed xml string.
& is easy to handle, just encode it to & ;.afer validation or transformation, decode it back.
My question is how to encode < sign in element value, seems can not just encode it to < ;, since it's hard to differieciated less than sign from open tag
If you have solution, share with me please.