draft-ietf-netmod-yang-tree-diagrams-00.txt   draft-ietf-netmod-yang-tree-diagrams-01.txt 
Network Working Group M. Bjorklund Network Working Group M. Bjorklund
Internet-Draft Tail-f Systems Internet-Draft Tail-f Systems
Intended status: Standards Track L. Berger, Ed. Intended status: Standards Track L. Berger, Ed.
Expires: December 15, 2017 LabN Consulting, L.L.C. Expires: December 31, 2017 LabN Consulting, L.L.C.
June 13, 2017 June 29, 2017
YANG Tree Diagrams YANG Tree Diagrams
draft-ietf-netmod-yang-tree-diagrams-00 draft-ietf-netmod-yang-tree-diagrams-01
Abstract Abstract
This document captures the current syntax used in YANG module Tree This document captures the current syntax used in YANG module Tree
Diagrams. The purpose of the document is to provide a single Diagrams. The purpose of the document is to provide a single
location for this definition. This syntax may be updated from time location for this definition. This syntax may be updated from time
to time based on the evolution of the YANG language. to time based on the evolution of the YANG language.
Status of This Memo Status of This Memo
skipping to change at page 1, line 34 skipping to change at page 1, line 34
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 15, 2017. This Internet-Draft will expire on December 31, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Tree Diagram Syntax . . . . . . . . . . . . . . . . . . . . . 2 2. Tree Diagram Syntax . . . . . . . . . . . . . . . . . . . . . 3
3. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Submodules . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 2.2. Groupings . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Informative References . . . . . . . . . . . . . . . . . . . 4 2.3. Collapsed Node Representation . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 2.4. Node Representation . . . . . . . . . . . . . . . . . . . 4
2.5. Extensions . . . . . . . . . . . . . . . . . . . . . . . 5
3. Usage Guidelines For RFCs . . . . . . . . . . . . . . . . . . 5
3.1. Wrapping Long Lines . . . . . . . . . . . . . . . . . . . 6
4. YANG Schema Mount Tree Diagrams . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Informative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
YANG Tree Diagrams were first published in [RFC7223]. Such diagrams YANG Tree Diagrams were first published in [RFC7223]. Such diagrams
are commonly used to provided a simplified graphical representation are commonly used to provided a simplified graphical representation
of a data model and can be automatically generated via tools such as of a data model and can be automatically generated via tools such as
"pyang". (See <https://github.com/mbj4668/pyang>). This document "pyang". (See <https://github.com/mbj4668/pyang>). This document
provides the syntax used in YANG Tree Diagrams. It is expected that provides the syntax used in YANG Tree Diagrams. It is expected that
this document will be updated or replaced as changes to the YANG this document will be updated or replaced as changes to the YANG
language, see [RFC7950], necessitate. language, see [RFC7950], necessitate.
Today's Common practice is include the definition of the syntax used Today's common practice is include the definition of the syntax used
to represent a YANG module in every document that provides a tree to represent a YANG module in every document that provides a tree
diagram. This practice has several disadvantages and the purpose of diagram. This practice has several disadvantages and the purpose of
the document is to provide a single location for this definition. It the document is to provide a single location for this definition. It
is not the intent of this document to restrict future changes, but is not the intent of this document to restrict future changes, but
rather to ensure such changes are easily identified and suitably rather to ensure such changes are easily identified and suitably
agreed upon. agreed upon.
An example tree diagram can be found in [RFC7223] Section 3. A An example tree diagram can be found in [RFC7223] Section 3. A
portion of which follows: portion of which follows:
skipping to change at page 2, line 51 skipping to change at page 3, line 10
| +--rw link-up-down-trap-enable? enumeration | +--rw link-up-down-trap-enable? enumeration
The remainder of this document contains YANG Tree Diagram syntax The remainder of this document contains YANG Tree Diagram syntax
based on output from pyang version 1.7.1. based on output from pyang version 1.7.1.
2. Tree Diagram Syntax 2. Tree Diagram Syntax
This section provides the meaning of the symbols used in YANG Tree This section provides the meaning of the symbols used in YANG Tree
diagrams. diagrams.
A full tree diagram of a module represents all elements. It includes
the name of the module and sections for top level module statements
(typically containers), augmentations, rpcs and notifications all
identified under a module statement. Module trees may be included in
a document as a whole, by one or more sections, or even subsets of
nodes.
A module is identified by "module:" followed the module-name. Top
level module statements are listed immediately following, offset by 4
spaces. Augmentations are listed next, offset by 2 spaces and
identified by the keyword "augment" followed by the augment target
node and a colon (':') character. This is followed by, RPCs which
are identified by "rpcs:" and are also offset by 2 spaces.
Notifications are last and are identified by "notifications:" and are
also offset by 2 spaces.
The relative organization of each section is provided using a text-
based format that is typical of a file system directory tree display
command. Each node in the tree is prefaces with '+--'. Schema nodes
that are children of another node are offset from the parent by 3
spaces. Schema peer nodes separated are listed with the same space
offset and, when separated by lines, linked via a pipe ('|')
character.
The full format, including spacing conventions is:
module: <module-name>
+--<node>
| +--<node>
| +--<node>
+--<node>
+--<node>
+--<node>
augment <target-node>:
+--<node>
+--<node>
+--<node>
+--<node>
rpcs:
+--<node>
+--<node>
notifications:
+--<node>
+--<node>
| +--<node>
+--<node>
2.1. Submodules
Submodules are represented in the same fashion as modules, but are
identified by "submodule:" followed the (sub)module-name. For
example:
submodule: <module-name>
+--<node>
| +--<node>
| +--<node>
2.2. Groupings
Nodes within a used grouping are expanded as if the nodes were
defined at the location of the uses statement.
2.3. Collapsed Node Representation
At times when the composition of the nodes within a module schema are
not important in the context of the presented tree, peer nodes and
their children can be collapsed using the notation '...' in place of
the text lines used to represent the summarized nodes. For example:
+--<node>
| ...
+--<node>
+--<node>
+--<node>
2.4. Node Representation
Each node in a YANG module is printed as: Each node in a YANG module is printed as:
<status> <flags> <name> <opts> <type> <if-features> <status> <flags> <name> <opts> <type> <if-features>
<status> is one of: <status> is one of:
+ for current + for current
x for deprecated x for deprecated
o for obsolete o for obsolete
<flags> is one of: <flags> is one of:
rw for configuration data rw for configuration data
ro for non-configuration data ro for non-configuration data
-x for rpcs and actions -x for rpcs and actions
-n for notifications -n for notifications
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<status> is one of: <status> is one of:
+ for current + for current
x for deprecated x for deprecated
o for obsolete o for obsolete
<flags> is one of: <flags> is one of:
rw for configuration data rw for configuration data
ro for non-configuration data ro for non-configuration data
-x for rpcs and actions -x for rpcs and actions
-n for notifications -n for notifications
mp for schema mount points
<name> is the name of the node <name> is the name of the node
(<name>) means that the node is a choice node (<name>) means that the node is a choice node
:(<name>) means that the node is a case node :(<name>) means that the node is a case node
If the node is augmented into the tree from another module, its If the node is augmented into the tree from another module, its
name is printed as <prefix>:<name>. name is printed as <prefix>:<name>.
<opts> is one of: <opts> is one of:
? for an optional leaf, choice, anydata or anyxml ? for an optional leaf, choice, anydata or anyxml
! for a presence container ! for a presence container
* for a leaf-list or list * for a leaf-list or list
[<keys>] for a list's keys [<keys>] for a list's keys
/ for a mounted module
@ for a node made available via a schema mount
parent reference
<type> is the name of the type for leafs and leaf-lists <type> is the name of the type for leafs and leaf-lists
If the type is a leafref, the type is printed as "-> TARGET", If the type is a leafref, the type is printed as "-> TARGET",
where TARGET is either the leafref path, with prefixed removed where TARGET is either the leafref path, with prefixed removed
if possible. if possible.
<if-features> is the list of features this node depends on, <if-features> is the list of features this node depends on,
printed within curly brackets and a question mark "{...}?" printed within curly brackets and a question mark "{...}?"
3. Next Steps 2.5. Extensions
Authors' note: This draft is currently a bit rough. The next/future TBD
version is expected to add text covering different types of trees and
when to use them; for example, complete module trees, subtrees, trees
for groupings etc. Maybe also how to deal with the limited line
lengths in RFCs.
4. IANA Considerations 3. Usage Guidelines For RFCs
This section provides general guidelines related to the use of tree
diagrams in RFCs. This section covers [Authors' note: will cover]
different types of trees and when to use them; for example, complete
module trees, subtrees, trees for groupings etc.
3.1. Wrapping Long Lines
Internet Drafts and RFCs limit the number of characters that may in a
line of text to 72 characters. When the tree representation of a
node results in line being longer than this limit the line should be
broken between <opts> and <type>. The type should be indented so
that the new line starts below <name> with a white space offset of at
least two characters. For example:
notifications:
+---n yang-library-change
+--ro module-set-id
-> /modules-state/module-set-id
The previously 'pyang' command can be helpful in producing such
output, for example the above example was produced using:
pyang -f tree --tree-line-length 50 < ietf-yang-library.yang
4. YANG Schema Mount Tree Diagrams
YANG Schema Mount is defined in [I-D.ietf-netmod-schema-mount] and
warrants some specific discussion. Schema mount document is a
generic mechanism that allows for mounting one data model consisting
of any number of YANG modules at a specified location of another
(parent) schema. Modules containing mount points will identify mount
points by name using the mount-point extension. These mount-points
should be identified, as indicated above using the 'mp' flag. For
example:
module: ietf-network-instance
+--rw network-instances
+--rw network-instance* [name]
+--rw name string
+--rw enabled? boolean
+--rw description? string
+--rw (ni-type)?
+--rw (root-type)?
+--:(vrf-root)
| +--mp vrf-root?
Note that a mount point definition alone is not sufficient to
identify if a mount point configuration or for non-configuration
data. This is determined by the yang-schema-mount module 'config'
leaf associated with the specific mount point.
In describing the intended use of a module containing a mount point,
it is helpful to show how the mount point would look with mounted
modules. In such cases, the mount point should be treated much like
a container that uses a grouping. The flags should also be set based
on the 'config' leaf mentioned above, and the mount realted options
indicated above should be shown. For example, the following
represents the prior example with YANG Routing and OSPF modules
mounted, YANG Interface module nodes accessible via a parent-
reference, and 'config' indicating true:
module: ietf-network-instance
+--rw network-instances
+--rw network-instance* [name]
+--rw name string
+--rw enabled? boolean
+--rw description? string
+--rw (ni-type)?
+--rw (root-type)?
+--:(vrf-root)
+--mp vrf-root?
+--ro rt:routing-state/
| ...
+--rw rt:routing/
| ...
+--ro if:interfaces@
| ...
+--ro if:interfaces-state@
...
The with 'config' indicating false, the only change would be to the
flag on the rt:routing node:
+--ro rt:routing/
5. IANA Considerations
There are no IANA requests or assignments included in this document. There are no IANA requests or assignments included in this document.
5. Informative References 6. Informative References
[I-D.ietf-netmod-schema-mount]
Bjorklund, M. and L. Lhotka, "YANG Schema Mount", draft-
ietf-netmod-schema-mount-05 (work in progress), May 2017.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface [RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<http://www.rfc-editor.org/info/rfc7223>. <http://www.rfc-editor.org/info/rfc7223>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016, RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>. <http://www.rfc-editor.org/info/rfc7950>.
Authors' Addresses Authors' Addresses
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