CIP-0059? | Terminology Surrounding Core Features (#274)

* CIP for names surrounding features

* feature table

* disambiguate protocol version from other schemes

* rename as CIP 59 and progress to Active

And also re-title as Terminology Surrounding Core Features

CIP-0059/README.md

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+---
+CIP: 59
+Title: Terminology Surrounding Core Features
+Authors: Jared Corduan <[email protected]>
+Status: Active
+Type: Informational
+Created: 2022-06-09
+License: CC-BY-4.0
+---
+
+## Simple Summary / Abstract
+
+This CIP seeks to clarify the language around groups of features.
+At the very least, it provides some history.
+
+## Motivation / History
+
+When @CharlesHoskinson conceived of Cardano, he had a vision for what features the network would support.
+This vision is still present on the [Cardano roadmap website](https://roadmap.cardano.org).
+In particular, the features are grouped into "phases", which are mostly named after poets (Goguen is the exception).
+The word "era" is used interchangeably with "phases" on the roadmap.
+
+The word "era", however, has been muddled by an implementation detail in the Cardano ledger.
+The Shelley phase was implemented as an entire re-write of the code from the Byron phase.
+While the consensus layer for the Shelley phase was written with an abstraction in place for the ledger,
+the ledger layer was not written with any abstractions to make future phases possible.
+Upon starting into the Goguen phase, the ledger team retroactively introduce a notion of "era"
+into the ledger code, and deemed the Shelley features "the Shelley era".
+In hindsight, however, the word "era" in unfortunate, since the Goguen phase was completed in the ledger
+by what was called "the Allegra era, the Mary era, the Alonzo era, and the Babbage era".
+The names Allegra and Mary were chosen for their connection to the poet Percy Shelley,
+and were only intended to be used as
+[variable names](https://github.com/input-output-hk/cardano-ledger/blob/1cbf1fc2bb005a8206e5b5a7cdf44d35baaca455/eras/shelley-ma/impl/src/Cardano/Ledger/Allegra.hs#L40)
+for a very specific abstraction used in the ledger code.
+(The story is even a bit more confusing, since the Allegra and Mary era share a lot of code
+and are specified together in the "Shelley-MA
+[specification](https://hydra.iohk.io/job/Cardano/cardano-ledger/specs.shelley-ma/latest/download-by-type/doc-pdf/shelley-ma).
+The letters "MA" can hilariously refer to both "Mary Allegra" and "Multi-Assets".)
+How did we then go from poets to Alonzo?
+Recall that "Goguen" was the only non-poet named in the phases on the Cardano roadmap.
+We found it fitting, therefore, to name the ledger era which introduced Plutus
+after the person who invented the lambda calculus
+(Plutus Core uses a variant of [system F](https://en.wikipedia.org/wiki/System_F).).
+Moreover, going forward, we decided to use names in A, B, C, ... order, names coming from
+other people who walk the line between mathematics and computer science.
+One lack of consistency to notice is that we have used both first and last names.
+The inconsistency was mostly driven by the desire to find short and memorable names.
+
+Another complication to the story is the notion of "intra-era hard forks".
+A new era _must_ be introduced with a hard fork, but the ledger can also
+change semantics during a controlled hard fork with another mechanism, namely
+an intra-era hard fork.
+This is an implementation detail which involves bumping the major protocol version
+but not creating a new ledger era.
+The Alonzo era experienced an intra-era hard fork when going from major protocol version 5 to 6.
+
+Yet another complication stems from the named releases.
+We chose to honor the late Cardano community member and Bulgarian mathematician Vasil Dabov
+by naming a release date after him.
+The ledger era after the Alonzo era was named Babbage.
+Babbage is a feature set, Vasil is a release date which ushered in the Babbage era.
+
+Lastly, it is important to understand that not all of the semantic changes to the Cardano network involve the ledger,
+though the changes to the ledger are often the most user-facing.
+Changes to the consensus protocol or the networking layer may also involve a hard fork.
+Moreover, there is an abstraction that sits between the consensus and ledger layers,
+which we have named the "protocol" (a regrettably vague name).
+The distinction between the ledger protocols and the ledger eras
+correspond roughly to how block headers are validated (protocol) versus
+how block bodies are validated (era).
+The Shelley era used the "transitional Praos" protocol (or TPraos for short).
+It consisted of Praos together with a transition system to move away from Ouroboros-BFT.
+The Babbage era replaced TPraos with Praos.
+
+A table of all the features, as of the time this CIP was submitted, can be found [here](feature-table.md).
+
+Note that the protocol version mentioned above is unrelated to the node-to-node and node-to-client protocol versions.
+The consensus layer maintains a versioning scheme for the node queries which does not necessarily
+align with the protocol version described in this CIP.
+
+Note also that the protocol version present inside of each block header indicates the maximum supported protocol version
+that the block producer is capable of supporting (see section 13, Software Updates, of the
+[Shelley ledger specification](https://hydra.iohk.io/job/Cardano/cardano-ledger/shelleyLedgerSpec/latest/download-by-type/doc-pdf/ledger-spec)).
+
+## Specification
+
+Let us use the following language:
+
+* **Phase** - A phase in Cardano is a high level collection of features described on the Cardano roadmap.
+* **Ledger Era** - A ledger era (or era for short if there is no confusion) in Cardano is a collection of ledger features introduced at a hard fork. Moreover, starting with the Alonzo era, they will be named after mathematicians and computer scientists (preferably both!) in A, B, C, ... ordering. Some letters might prove challenging.
+* **Intra-era Hardfork** - An intra-era hard fork in Cardano is a small and focused semantic change to the ledger which requires a hard fork.
+* **Consensus mechanism** - A consensus mechanism in Cardano is a collection of consensus features introduced at a hard fork. Historically, these have had the name "Ouroboros" in them.
+* **Ledger Protocol** - A ledger protocol in Cardano is a collection of ledger features sitting between the consensus layer and the ledger layer, roughly characterized by block header validation.
+* **Release Dates** - When we are confident about the release of a new features, we can chose to honor Cardano community members by naming a date after them.
+
+
+## Rationale
+
+If we can agree to common language, it will greatly improve communication among ourselves and also with new community members.
+
+## Backwards compatibility
+
+Since this is an issue of language, we will strive to use consistent language going forward, and we can correct misalignment when we find it.
+
+## Path to Active
+
+We will use this CIP as our common language going forward.
+
+## Copyright
+
+This CIP is licensed under Apache-2.0

CIP-namesSurroundingFeatures/feature-table.md

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+# Cardano Features
+
+| Date    | Phase   | Era     | Slot Number | Epoch Number | Protocol Version | Ledger Protocol | Consensus Mechanism | Notes              |
+| ------- | ------- | -------:| -----------:| ------------:| ----------------:| ---------------:| -------------------:| ------------------:|
+| 2017/09 | Byron   | Byron   | 0           | 0            | 0,0              | -               | Ouroboros Classic   |                    |
+| 2020/02 | Byron   | Byron   | 3801600     | 176          | 1,0              | -               | Ouroboros BFT       |                    |
+| 2020/07 | Shelley | Shelley | 4492800     | 208          | 2,0              | TPraos          | Ouroboros Praos     |                    |
+| 2020/12 | Goguen  | Allegra | 16588800    | 236          | 3,0              | TPraos          | Ouroboros Praos     |                    |
+| 2021/03 | Goguen  | Mary    | 23068800    | 251          | 4,0              | TPraos          | Ouroboros Praos     |                    |
+| 2021/09 | Goguen  | Alonzo  | 39916975    | 290          | 5,0              | TPraos          | Ouroboros Praos     |                    |
+| 2021/10 | Goguen  | Alonzo  | 43372972    | 298          | 6,0              | TPraos          | Ouroboros Praos     | intra-era hardfork |
+|         | Goguen  | Babbage |             |              | 7,0              |  Praos          | Ouroboros Praos     | Vasil HF           |