As part of my involvement with the +Nikita +Noark 5 core project, I have been proposing improvements to the +API specification created by The +National Archives of Norway and helped migrating the text from a +version control system unfriendly binary format (docx) to Markdown in +git. Combined with the migration to a public git repository (on +github), this has made it possible for anyone to suggest improvement +to the text.
+ +The specification is filled with UML diagrams. I believe the +original diagrams were modelled using Sparx Systems Enterprise +Architect, and exported as EMF files for import into docx. This +approach make it very hard to track changes using a version control +system. To improve the situation I have been looking for a good text +based UML format with associated command line free software tools on +Linux and Windows, to allow anyone to send in corrections to the UML +diagrams in the specification. The tool must be text based to work +with git, and command line to be able to run it automatically to +generate the diagram images. Finally, it must be free software to +allow anyone, even those that can not accept a non-free software +license, to contribute.
+ +I did not know much about free software UML modelling tools when I +started. I have used dia and inkscape for simple modelling in the +past, but neither are available on Windows, as far as I could tell. I +came across a nice +list +of text mode uml tools, and tested out a few of the tools listed +there. The PlantUML tool seemed +most promising. After verifying that the packages +is available in +Debian and found its +Java source under a GPL license on github, I set out to test if it +could represent the diagrams we needed, ie the ones currently in +the +Noark 5 Tjenestegrensesnitt specification. I am happy to report +that it could represent them, even thought it have a few warts here +and there.
+ +After a few days of modelling I completed the task this weekend. A +temporary link to the complete set of diagrams (original and from +PlantUML) is available in +the +github issue discussing the need for a text based UML format, but +please note I lack a sensible tool to convert EMF files to PNGs, so +the "original" rendering is not as good as the original was in the +publised PDF.
+ +Here is an example UML diagram, showing the core classes for +keeping metadata about archived documents:
+ ++@startuml +skinparam classAttributeIconSize 0 + +!include media/uml-class-arkivskaper.iuml +!include media/uml-class-arkiv.iuml +!include media/uml-class-klassifikasjonssystem.iuml +!include media/uml-class-klasse.iuml +!include media/uml-class-arkivdel.iuml +!include media/uml-class-mappe.iuml +!include media/uml-class-merknad.iuml +!include media/uml-class-registrering.iuml +!include media/uml-class-basisregistrering.iuml +!include media/uml-class-dokumentbeskrivelse.iuml +!include media/uml-class-dokumentobjekt.iuml +!include media/uml-class-konvertering.iuml +!include media/uml-datatype-elektronisksignatur.iuml + +Arkivstruktur.Arkivskaper "+arkivskaper 1..*" <-o "+arkiv 0..*" Arkivstruktur.Arkiv +Arkivstruktur.Arkiv o--> "+underarkiv 0..*" Arkivstruktur.Arkiv +Arkivstruktur.Arkiv "+arkiv 1" o--> "+arkivdel 0..*" Arkivstruktur.Arkivdel +Arkivstruktur.Klassifikasjonssystem "+klassifikasjonssystem [0..1]" <--o "+arkivdel 1..*" Arkivstruktur.Arkivdel +Arkivstruktur.Klassifikasjonssystem "+klassifikasjonssystem [0..1]" o--> "+klasse 0..*" Arkivstruktur.Klasse +Arkivstruktur.Arkivdel "+arkivdel 0..1" o--> "+mappe 0..*" Arkivstruktur.Mappe +Arkivstruktur.Arkivdel "+arkivdel 0..1" o--> "+registrering 0..*" Arkivstruktur.Registrering +Arkivstruktur.Klasse "+klasse 0..1" o--> "+mappe 0..*" Arkivstruktur.Mappe +Arkivstruktur.Klasse "+klasse 0..1" o--> "+registrering 0..*" Arkivstruktur.Registrering +Arkivstruktur.Mappe --> "+undermappe 0..*" Arkivstruktur.Mappe +Arkivstruktur.Mappe "+mappe 0..1" o--> "+registrering 0..*" Arkivstruktur.Registrering +Arkivstruktur.Merknad "+merknad 0..*" <--* Arkivstruktur.Mappe +Arkivstruktur.Merknad "+merknad 0..*" <--* Arkivstruktur.Dokumentbeskrivelse +Arkivstruktur.Basisregistrering -|> Arkivstruktur.Registrering +Arkivstruktur.Merknad "+merknad 0..*" <--* Arkivstruktur.Basisregistrering +Arkivstruktur.Registrering "+registrering 1..*" o--> "+dokumentbeskrivelse 0..*" Arkivstruktur.Dokumentbeskrivelse +Arkivstruktur.Dokumentbeskrivelse "+dokumentbeskrivelse 1" o-> "+dokumentobjekt 0..*" Arkivstruktur.Dokumentobjekt +Arkivstruktur.Dokumentobjekt *-> "+konvertering 0..*" Arkivstruktur.Konvertering +Arkivstruktur.ElektroniskSignatur -[hidden]-> Arkivstruktur.Dokumentobjekt +@enduml ++ +
The format is quite +compact, with little redundant information. The text expresses +entities and relations, and there is little layout related fluff. One +can reuse content by using include files, allowing for consistent +naming across several diagrams. The include files can be standalone +PlantUML too. Here is the content of +media/uml-class-arkivskaper.iuml:
+ ++@startuml +class Arkivstruktur.Arkivskaper+ +{ + +arkivskaperID : string + +arkivskaperNavn : string + +beskrivelse : string [0..1] +} +@enduml +
This is what the complete diagram for the PlantUML notation above +look like:
+ +
A cool feature of PlantUML is that the generated PNG files include +the entire original source diagram as text. The source (with include +statements expanded) can be extracted using for example +exiftool. Another cool feature is that parts of the entities +can be hidden after inclusion. This allow to use include files with +all attributes listed, even for UML diagrams that should not list any +attributes.
+ +The diagram also show some of the warts. Some times the layout +engine place text labels on top of each other, and some times it place +the class boxes too close to each other, not leaving room for the +labels on the relationship arrows. The former can be worked around by +placing extra newlines in the labes (ie "\n"). I did not do it here +to be able to demonstrate the issue. I have not found a good way +around the latter, so I normally try to reduce the problem by changing +from vertical to horizontal links to improve the layout.
+ +All in all, I am quite happy with PlantUML, and very impressed with +how quickly its lead developer responds to questions. So far I got an +answer to my questions in a few hours when I send an email. I +definitely recommend looking at PlantUML if you need to make UML +diagrams. Note, PlantUML can draw a lot more than class relations. +Check out the documention for a complete list. :)
+ +As usual, if you use Bitcoin and want to show your support of my +activities, please send Bitcoin donations to my address +15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.
+