<p>Yes, a validator is called prior to the start of the transaction as it part of the constraints that determines if the transaction can proceed. A validator that executes on-chain has no visibility of past transactions. It can only see the transaction it belongs to, its inputs and input data supplied to the validator.<br />
It is the off-chain code that constructs the transaction that has visibility of the full blockchain of past transactions.</p>

CC BY-SA 4.0
2021-08-13T17:21:35.997Z
2021-08-13T17:21:35.997Z
vcwebco
<p>A validator is called <strong>prior</strong> to transaction's start (not to mention completion). But yet a validator routinely checks if a potential recipient has <strong>already</strong> received his funds, and other such tests about events in the past.</p>
<p>So is the validator <strong>pretending</strong> that the transaction has already completed, whereas in truth the transaction has not yet started -- and perhaps never will?</p>

<plutus><plutustx>
Are Validators pretending transaction already completed?
# Are Validators pretending transaction already completed?

(Asked by: username_0 on 2021-08-13)

A validator is called **prior** to transaction's start (not to mention completion). But yet a validator routinely checks if a potential recipient has **already** received his funds, and other such tests about events in the past.

So is the validator **pretending** that the transaction has already completed, whereas in truth the transaction has not yet started -- and perhaps never will?

**Tags:** plutus, plutustx

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## 1 answers

### Answer by username_1 on 2021-08-13. Score: 2 | Accepted answer

Yes, a validator is called prior to the start of the transaction as it part of the constraints that determines if the transaction can proceed. A validator that executes on-chain has no visibility of past transactions. It can only see the transaction it belongs to, its inputs and input data supplied to the validator.  
It is the off-chain code that constructs the transaction that has visibility of the full blockchain of past transactions.


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