The rule of thumb to distinguish the two phenomena is as follows: when an expression refers to another linguistic expression or a piece of discourse, it is discourse deictic.
The former is used as if the words being used were those of another, which are therefore pivoted to a deictic center different from the speech situation of the report.
The basic formal pattern of the demonstratives is that the initial consonant and ending vowel nucleus indicate their function and position in the deictic system.
Spatial modulations can perform various functions including indicating person or number; providing deictic, locative, or temporal information; or indicating grammatical relationships.