UMLOutput

Introduction

In some circumstances it is useful to be able to visualize YANG models as UML diagrams. Pyang supports two different ways of doing this:

• Render png using PlantUML: pyang -f uml
• Generate XMI (soon) which can be imported to ArgoUML : pyang -f xmi

XMI for ArgoUML

I have given up on the I in XMI, the output only works for ArgoUML. Convince me that UML XMI is an interoperable standard.

pyang -f xmi ietf-netconf-acm.yang -o ietf-netconf-acm.xmi

Then you can start ArgoUML and chose XMI Import. The easiest way is then to drag all or selected classes into the diagram and ask ArgoUML to auto-layout (Arrange - layout). After that, make the diagram look as you want.

The tagged values tab will show YANG specifics like config, status, mandatory etc. If you select a class you get the tagged values for the container, list, if you select an attribute you get it for the leaf/leaf-list.

PlantUML output

The uml plugin to pyang generates a file that can be read by plantuml.

The following example converts the ietf-netconf-monitoring module into a UML diagram:

$ pyang -f uml ietf-netconf-monitoring.yang -o ietf-netconf-monitoring.uml
$ java -jar plantuml.jar ietf-netconf-monitoring.uml 
$ open img/ietf-netconf-monitoring.png

On some platforms Java might spit out "java.lang.OutOfMemoryError: Java heap space"

Pass the -Xmx<SIZE>m to java like:

$ java -Xmx1024m -jar plantuml.jar ietf-netconf-monitoring.uml 

Please note that the uml output has numerous options to tweak and simplify the layout. To skip details try the --uml-no= parameter. In many cases you like to inline augments and groupings, use the --uml-inline parameters.

You can also pass several YANG files to the UML output format, but the files must be given in dependency order. (Multi-file does not work for module/sub-module dependancies)

Another example with some parts suppressed:

$ pyang -f uml --uml-no=circles,stereotypes,annotation ietf-netconf-monitoring.yang -o ietf-netconf-monitoring.uml

A multi-file example from the ongoing YANG modeling in Metro Ethernet Forum

A complex example based on the Configuration Data Model for IPFIX and PSAMP

There is also a python script to generate a UML package structure for all yangs in a folder.

uml-utilities/uml-pkg

Use it in the following way:

$ ls *.yang | xargs -n1 pyang -f depend > packages.txt
$ uml-pkg --title=TITLE --inputfile=packages.txt > packages.uml
$ java -jar plantuml.jar packages.uml
$ open img/packages.png