Are there indications/rules when to let a note ring longer than its actual value
 

For example: in Capricho Arabe the first harmonics are written as*dotted half notes but*i am supposed to hold it for the whole next bar. Same goes for the main theme: the bass notes are written as quater notes but when i*see guitarists playing*it they play the first bass note as a whole note.

Are these things generally left open*for interpretation or*are there rules for how long to hold a note?