Concept Of Relative Future In Sanskrit

Case 1:

Case 1A
saH AsIt -> "sah kim kurvan AsIt ?" -> "sah paThan AsIt" or "sah paThiShyan AsIt"

        paThan AsIt =           Odutta idda = "he was there (being) the one who (is)         reading" or simply "he was reading"

paThiShyan AsIt = OduvavanAgi idda = "he was there (being) the one who (will be) reading" ?

conveys the meaning that he was there about to read in future.or with an intent to become the one who reads.

Case 1B

saH asti -> "sah kim kurvan asti ?" -> "sah paThan asti" or "sah paThiShyan asti"

        paThan asti =           Odutta iddAne = "he is there (being) the one who (is)         reading" or simply "he is reading"

paThiShyan asti = OduvavanAgi iddAne = "he is there (being) the one who (will be) reading"

Case 1C

saH bhaviShyati -> "sah kim kurvan bhaviShyati?" -> "sah paThan bhaviShyati " or "sah paThiShyan bhaviShyati "

        paThan bhaviShyati =           Odutta iruttAne = "he will be there (being) the one who (is)         reading" or simply "he will be reading"

paThiShyan bhaviShyati = OduvavanAgi iruttAne = "he will be there (being) the one who (will be) reading" 

Here, paThiShyan is relative future to 'AsIt/asti/bhaviShyati'

similarly

Case 2:

Case 2A: 

सः      पठन् (Relative Future) अगच्छत् (Past) = "He Came (being) the one who  (is)         reading"

सः पठिष्यन् (Relative Future) अगच्छत् (Past)  = "He Came (being) the one who (will be) reading"

Case 2B: 

सः      पठन् (Relative Future) अगमिष्यति (Future)  = "He Will Come (being) the one who (is)         reading"

सः पठिष्यन् (Relative Future) अगमिष्यति (Future)  = "He Will Come (being) the one who (will be) reading"

Case 2C: 

सः      पठन् (Relative Future) अगच्छति (Present) = "He Comes (being) the one who (is)         reading"

सः पठिष्यन् (Relative Future) अगच्छति (Present) = "He Comes (being) the one who (will be) reading"

similarly

Case 3:

Case 3A: 

सः      पठन् (Relative Future) अलिखत् (Past) = "He Wrote (being) the one who  (is)         reading"

सः पठिष्यन् (Relative Future) अलिखत् (Past)  = "He Wrote (being) the one who (will be) reading"

Case 3B: 

सः      पठन् (Relative Future) लेखिष्यति (Future)  = "He Will Write (being) the one who (is)         reading"

सः पठिष्यन् (Relative Future) लेखिष्यति (Future)  = "He Will Write (being) the one who (will be) reading"

Case 3C: 

सः      पठन् (Relative Future) लिखति (Present) = "He Writes (being) the one who (is)         reading"

सः पठिष्यन् (Relative Future) लिखति (Present) = "He Writes (being) the one who (will be) reading"

paThan can be seen as a Present Continuous Participle

paThiShyan can be seen as a Relative Future Participle

paThan is the "shatr" pratyaya form of paTh dhAtu