Update README.md

Author: fxamacker

README.md

@@ -1,13 +1,23 @@
 
 # Cadence Compact Format (CCF)
 
-Cadence Compact Format (CCF) is a data format designed for compact, efficient, and deterministic encoding of [Cadence](https://github.com/onflow/cadence) external values.  CCF is defined in [ccf_specs.md](ccf_specs.md).
+CCF is defined in [ccf_specs.md](ccf_specs.md).
+
+The [CCF codec](https://github.com/onflow/cadence/tree/master/encoding/ccf) in Cadence is used for encoding events in CCF.  However, some CCF options are not yet implemented in the codec.
+
+"Abstract" and "Introduction" sections in this README were copied from the CCF specs.  Additional content such as benchmarks will be added to the README later.
+
+## Abstract
+
+Cadence Compact Format (CCF) is a data format designed for compact, efficient, and deterministic encoding of [Cadence](https://github.com/onflow/cadence) external values.
 
 Cadence is a resource-oriented programming language that introduces new features to smart contract programming.  It's used by [Flow](https://github.com/onflow/flow-go) blockchain and has a syntax inspired by Swift, Kotlin, and Rust. Its use of resource types maps well to the Move language.
 
-CCF can be used as a hybrid data format.  CCF-based messages can be fully self-describing or partially self-describing.  Both are more compact than JSON-based messages.  CCF-based protocols can send Cadence metadata just once for all messages of that type.  Malformed data can be detected without Cadence metadata and without creating Cadence objects.
+CCF messages can be fully self-describing or partially self-describing.  Both are more compact than JSON-based messages.  CCF-based protocols can send Cadence metadata just once for all messages of that type.  Malformed data can be detected without Cadence metadata and without creating Cadence objects.
 
-CCF obsoletes [JSON-Cadence Data Interchange Format](https://developers.flow.com/cadence/json-cadence-spec) for use cases that do not require JSON.
+CCF defines "Deterministic CCF Encoding Requirements" and makes it optional.  It allows CCF codecs implemented in different programming languages to produce the same deterministic encodings.  CCF-based formats and protocols can balance tradeoffs by specifying how they use CCF options.
+
+CCF obsoletes [JSON-Cadence Data Interchange Format](https://developers.flow.com/cadence/json-cadence-spec) (JSON-CDC) for use cases that do not require JSON.
 
 ### Introduction
 
@@ -28,6 +38,12 @@ CCF uses CBOR and is designed to allow efficient detection and rejection of malf
 
 CBOR is an [Internet Standard](https://www.ietf.org/rfc/std-index.txt) defined by [IETF STD 94](https://www.rfc-editor.org/info/std94).  CBOR is designed to be relevant for decades and is used by data formats and protocols such as [W3C WebAuthn](https://www.w3.org/TR/webauthn-2/), C-DNS ([IETF RFC 8618](https://www.rfc-editor.org/rfc/rfc8618.html)), COSE ([IETF STD 96](https://www.rfc-editor.org/info/std96)), CWT ([IETF RFC 8392](https://www.rfc-editor.org/info/rfc8392)), etc.
 
+## History
+
+Commit history and contributions to `ccf_specs.md` file prior to Nov 29, 2022 are associated with `README.md` file.
+
+Old branches can be found at https://github.com/fxamacker/ccf_draft.
+
 ## License
 
 CCF is licensed under the terms of the Apache License, Version 2.0. See [LICENSE](LICENSE) for more information.