ADR - untranslatable data in script context

docs/adr/2022-12-05_004-untranslatable-data-in-script-context.md

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+---
+slug: 4
+title: |
+  4. Untranslatable data in script context
+authors: [Jared Corduan]
+tags: [Accepted]
+---
+
+## Status
+
+Accepted
+
+## Context
+
+Sometimes there is data in a transaction which a Plutus script author might
+expect to be present in the script context, but which we do not want to translate. 
+One example is the legacy Byron addresses.
+Another example is the features which were added to the Babbage ledger era
+(such as inline datums) which are not a part of the Plutus V1 script context since they did not
+exist when Plutus V1 was released.
+
+
+There are basically two options for dealing with such information:
+1. Silently ignore parts of the relevant script context during the translation.
+2. Force a phase 1 validation error.
+
+## Decision
+
+We chose option 2, since option 1 could lead to surprising and unfortunate mistakes by
+script authors.
+
+## Consequences
+
+Scripts will fail phase 1 validation if used in a transaction that contains data not available
+for the corresponding script context.
+For example, one cannot spend a Plutus V1 output and pay to a Plutus V2 output with
+inline datum at the same time.
+
+See this test suite for the list of untranslatable data at the time of the creation of this ADR:
+
+https://github.com/input-output-hk/cardano-ledger/blob/064acb8e7ab7b2aeef138ec0c821f8c5f1402621/eras/babbage/test-suite/test/Test/Cardano/Ledger/Babbage/TxInfo.hs#L190-L193