Tock Reference Document (TRD) Structure and Keywords

TRD: 1
Working Group: Kernel
Type: Best Common Practice
Status: Final
Authors: Philip Levis, Daniel Griffin


This document describes the structure followed by all Tock Reference Documents (TRDs), and defines the meaning of several key words in those documents.

1 Introduction

To simplify management, reading, and tracking development, all Tock Reference Documents (TRDs) MUST have a particular structure. Additionally, to simplify development and improve implementation interoperability, all TRDs MUST observe the meaning of several key words that specify levels of compliance. This document describes and follows both.

2 Keywords

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in TRD1.

Note that the force of these words is modified by the requirement level of the document in which they are used. These words hold their special meanings only when capitalized, and documents SHOULD avoid using these words uncapitalized in order to minimize confusion.

2.1 MUST

MUST: This word, or the terms "REQUIRED" or "SHALL", mean that the definition is an absolute requirement of the document.


MUST NOT: This phrase, or the phrase "SHALL NOT", mean that the definition is an absolute prohibition of the document.


SHOULD: This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.


SHOULD NOT: This phrase, or the phrase "NOT RECOMMENDED" mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label.

2.5 MAY

MAY: This word, or the adjective "OPTIONAL", mean that an item is truly optional. One implementer may choose to include the item because a particular application requires it or because the implementer feels that it enhances the system while another implementer may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. Similarly, an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.)

2.6 Guidance in the use of these Imperatives

Imperatives of the type defined in this memo must be used with care and sparingly. In particular, they MUST only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmissions) For example, they must not be used to try to impose a particular method on implementors where the method is not required for interoperability.

3 TRD Structure

A TRD MUST begin with a title, and then follow with a header and a body. The header states document metadata, for management and status. The body contains the content of the proposal.

All TRDs MUST conform to Markdown syntax to enable translation to HTML and LaTeX, and for useful display in web tools.

3.1 TRD Header

The TRD header has several fields which MUST be included, as well as others which MAY be included. The TRD header MUST NOT include fields which are not specified in TRD 1 or supplementary Best Common Practice TRDs. The first five header fields MUST be included in all TRDs, in the order stated below. The Markdown syntax to use when composing a header is modeled by this document's header.

The first field is "TRD," and specifies the TRD number of the document. A TRD's number is unique. This document is TRD 1. The TRD type (discussed below) determines TRD number assignment. Generally, when a document is ready to be a TRD, it is assigned the smallest available number. BCP TRDs start at 1 and all other TRDs (Documentary, Experimental, and Informational) start at 101.

The second field, "Working Group," states the name of the working group that produced the document. This document was produced by the Kernel Working Group.

The third field is "Type," and specifies the type of TRD the document is. There are four types of TRD: Best Current Practice (BCP), Documentary, Informational, and Experimental. This document's type is Best Current Practice.

Best Current Practice is the closest thing TRDs have to a standard: it represents conclusions from significant experience and work by its authors. Developers desiring to add code (or TRDs) to Tock SHOULD follow all current BCPs.

Documentary TRDs describe a system or protocol that exists; a documentary TRD MUST reference an implementation that a reader can easily obtain. Documentary TRDs simplify interoperability when needed, and document Tock implementations.

Informational TRDs provide information that is of interest to the community. Informational TRDs include data gathered on radio behavior, hardware characteristics, other aspects of Tock software/hardware, organizational and logistic information, or experiences which could help the community achieve its goals.

Experimental TRDs describe a completely experimental approach to a problem, which are outside the Tock release stream and will not necessarily become part of it. Unlike Documentary TRDs, Experimental TRDs may describe systems that do not have a reference implementation.

The fourth field is "Status," which specifies the status of the TRD. A TRD's status can be either "Draft," which means it is a work in progress, or "Final," which means it is complete and will not change. Once a TRD has the status "Final," the only change allowed is the addition of an "Obsoleted By" field.

The "Obsoletes" field is a backward pointer to an earlier TRD which the current TRD renders obsolete. An Obsoletes field MAY have multiple TRDs listed. For example, if TRD 121 were to replace TRDs 111 and 116, it would have the field "Obsoletes: 111, 116".

The "Obsoleted By" field is added to a Final TRD when another TRD has rendered it obsolete. The field contains the number of the obsoleting TRD. For example, if TRD 111 were obsoleted by TRD 121, it would have the field "Obsoleted By: 121".

"Obsoletes" and "Obsoleted By" fields MUST agree. For a TRD to list another TRD in its Obsoletes field, then that TRD MUST list it in the Obsoleted By field.

The obsoletion fields are used to keep track of evolutions and modifications of a single abstraction. They are not intended to force a single approach or mechanism over alternative possibilities.

The final required field is "Authors," which states the names of the authors of the document. Full contact information should not be listed here (see Section 3.2).

There is an optional field, "Extends." The "Extends" field refers to another TRD. The purpose of this field is to denote when a TRD represents an addition to an existing TRD. Meeting the requirements of a TRD with an Extends field requires also meeting the requirements of all TRDs listed in the Extends field.

If a TRD is a Draft, then four additional fields MUST be included: Draft-Created, Draft-Modified, Draft-Version, and Draft-Discuss. Draft-Created states the date the document was created, Draft-Modified states when it was last modified. Draft-Version specifies the version of the draft, which MUST increase every time a modification is made. Draft-Discuss specifies the email address of a mailing list where the draft is being discussed. Final and Obsolete TRDs MUST NOT have these fields, which are for Drafts only.

3.2 TRD Body

A TRD body SHOULD begin with an Abstract, which gives a brief overview of the content of the TRD. A longer TRD MAY, after the Abstract, have a Table of Contents. After the Abstract and Table of Contents there SHOULD be an Introduction, stating the problem the TRD seeks to solve and providing needed background information.

If a TRD is Documentary, it MUST have a section entitled "Implementation," which instructs the reader how to obtain the implementation documented.

If a TRD is Best Current Practice, it MUST have a section entitled "Reference," which points the reader to one or more reference uses of the practices.

The last three sections of a TRD are author information, citations, and appendices. A TRD MUST have an author information section titled entitled "Author's Address" or "Authors' Addresses." A TRD MAY have a citation section entitled "Citations." A citations section MUST immediately follow the author information section. A TRD MAY have appendices. Appendices MUST immediately follow the citations section, or if there is no citations section, the author information section. Appendices are lettered. Please refer to Appendix A for details.

4 File names

TRDs MUST be stored in the Tock repository with a file name of


Where number is the TRD number and desc is a short, one word description. The name of this document is

5 Reference

The reference use of this document is TRD 1 (itself).

6 Acknowledgments

The definitions of the compliance terms are a direct copy of definitions taken from IETF RFC 2119. This document is heavily copied from TinyOS Enhancement Proposal 1 (TEP 1).

7 Author's Address

Philip Levis
409 Gates Hall
Stanford University
Stanford, CA 94305

phone - +1 650 725 9046

email -

Appendix A Example Appendix

This is an example appendix. Appendices begin with the letter A.