THere are number of standards that define protocols[rules] for transactions [be it financial or non financial – ]. these standards ecusre consistency in excahneg of information between difeernt entities envlolevd(bank[acquirer,issuer,]merchant,user) . e.g one of the stadnrd that is widely used internationally ISO20022[for all paymentISO 8583 [specicically for card payment]] ,others include ACH managed by ACHA
On similar line in india we have a payment standrd called UPI[Unified payment interface] manaed by NPCI[National Payment COrportatoin of INdia]
In UPI standrd of payment, it defines set of protocols in a specific forrmal[xml with header,body etc] used by invloded parties for transacation.
sample
<upi:phase>
<header> -- version </Header>
<Meta> type of phases</Meta>
<Txn> -txn details -C|D|CR|DR|R
<Rules>- primarily for mandates- for expiry time
</Txn>
<Payer namr""> -- payer details</Payer>
<Payee> - payee ddetails </payee>
</upi:phase>
Note: std structured as elements of xmls i.e root, childs i.e header,meta,txn,payer , payee etc. and elements have attributes e.g name in payer that add additional information .
Tranasction has different phases OR is managed by different APIs and
there are protocol related to each phases \APIs- reqpay,respay , req-auth,respauth, req-paycollect , reqpay-intent, reqpay-mandate, resp-paymandate []
above mentoined protocol are used with varitoues instruments[cards,lite-payment,FIR,wallet-transaction etc.] with variation in the parameters/atributes/elemnts passed as part of standed protocol.
We can go in more deplth of each phases as folllowops posts.
Techglot 