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Internet-Draft The Concise Data Definition Language (CDDL), standardized in RFC 8610, is defined to provide data models for data shaped like JSON or CBOR. Another representation format that is quote popular is the CSV (Comma-Separated Values) file as defined by RFC 4180. The present document shows a way how to use CDDL to provide a data model for CSV files.

Introduction The Concise Data Definition Language (CDDL), standardized in , is defined to provide data models for data shaped like JSON or CBOR. Another representation format that is quote popular is the CSV file as defined by . The present document shows how to use CDDL to provide a data model for CSV files.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. This specification uses terminology from .

CSV generic data model The CSV format is defined in . The generic data model for the data in a CSV file can be described in CDDL as: Note that the elements of this data model describe the interpretation of the data after processing and removal of lexical structure such as newlines, commas, escape characters, and quotation marks. For the purposes of a specific application, the data model level structure of each field may be described in a more elaborate way, e.g., as a number. CDDL currently does not have a way to express the transformation from the text string in the CSV field to the number that this text string represents at the application data model level; the usage of anything but "text" for a field therefore MUST be accompanied by an instruction how to perform the translation. As a preferred choice, the JSON representation of the data model item, if it exists, MAY be chosen by that instruction. Since the CSV media type text/csv defaults to using the US-ASCII character set (i.e., ; see ), many uses of CSV will need to specify the media type parameter charset. (Note that CDDL can describe text information that is in UTF-8 form, which includes US-ASCII as that is a subset of UTF-8. If a different form that is not a subset of UTF-8 is really still needed, some rules for conversion will need to be defined by the application.) The media type parameter header MAY be used to indicate the presence or absence of a header line; if it is not given, the grammar MUST NOT be ambiguous about the presence of a header (i.e., it MUST be either mandatory or absent). Note that the ABNF in does not quite handle the case that charset is not us-ascii. For the purposes of the present specification, the ABNF is understood to allow all characters from the charset except %x22 and %x2C in TEXTDATA. For the purposes of the present specification, the ABNF rule CRLF is read as: as is hinted in .

Examples A simplified CSV form definition of a SID file might look like this: TODO: show the example in

IANA Considerations This document makes no requests of IANA.

Security considerations The security considerations of and apply.

References Normative References This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON. This RFC documents the format used for Comma-Separated Values (CSV) files and registers the associated MIME type "text/csv". This memo provides information for the Internet community. Internet technical specifications often need to define a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. The current specification documents ABNF. It balances compactness and simplicity with reasonable representational power. The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges. This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. [STANDARDS-TRACK] In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References Trilliant Networks Inc. Acklio Google Switzerland GmbH Universität Bremen TZI Sandelman Software Works YANG Schema Item iDentifiers (YANG SID) are globally unique 63-bit unsigned integers used to identify YANG items, as a more compact method to identify YANG items that can be used for efficiency and in constrained environments (RFC 7228). This document defines the semantics, the registration, and assignment processes of YANG SIDs for IETF managed YANG modules. To enable the implementation of these processes, this document also defines a file format used to persist and publish assigned YANG SIDs. // The present version (-19) adds in draft text about objectives, // parties, and roles. This attempts to record discussions at side // meetings before, at, and after IETF 113.

Acknowledgements Rob Wilton, unknowingly, made me write this specification. I hope it will be useful.