Wednesday, November 01, 2006

Going Dotty

There's a new big thing in my sphere of interest: Dotty.

For the uninitiated: Dotty, Neato and Lefty are a family of products from Graphviz that take pretty simple text files and generate directed or un-directed graphs.

For the initiated: No, I can't believe I've never found it before either!

It was name checked during the Google LTAC by at least one presenter, and they reminded me that I'd heard its name quite some time ago and meant to look it up. When we were looking at a diagramming problem just a few weeks ago and I figured I should track it down. I was by no means disappointed.

Basically we wanted something that would graph our MVC workflow configurations to make them more readable.

That is, our MVC structure allows us to string arbitrary tasks together: perform x, if result is y, go to task z, if result is h go to task i.

The idea is to keep these configurations as simple as possible; they're only really receiving user input and then prodding objects, but still, there are some complexities. This is especially true when branches split and rejoin. For some reason, XML files or a PHP arrays can be difficult to read ;-)

Quite a long time ago we wrote a small application that would graph them in HTML, but we never liked its results. When paths split and rejoin, the HTML representation wouldn’t show the rejoin.

So, as I say, we picked up Dotty.

Simply genius.

For directional graphs the Dot output is stunning. We can pass it a file in (the trivially simple) Dot language and it'll produce great looking diagrams.
For example, the file:

digraph finite_state_machine {
node [ fontsize="12", fontname="arial"]
edge [ fontsize="8", fontname="arial" ]
EntryPoint [ label="EntryPoint (BuildSheepFromInput)", shape="diamond" ];
EntryPoint->SaveEditedSheep [ label="DEFAULT" ];
SaveEditedSheep [ label="SaveEditedSheep (SaveEditedSheepTask)" ];
SaveEditedSheep->SaveCheese [ label="DEFAULT" ];
EditSheep__EntryPoint [ shape="box" ];
SaveEditedSheep->EditSheep__EntryPoint [ label="ERRORS" ];
SaveCheese [ label="SaveCheese (SaveCheeseTask)" ];
SaveCheese->GetCheeseType [ label="DEFAULT" ];
GetCheeseType [ label="GetCheeseType (GetCheeseTypeTask)" ];
DisplayWensleydale__EntryPoint [ shape="box" ];
GetCheeseType->DisplayWensleydale__EntryPoint [ label="WENSLEYDALE" ];
GetCheeseType->DisplayCheddar__ComposeMessage [ label="CHEDDAR" ];

Would produce:
SaveCheeseWorkflow – Example DOT image


It's not difficult to write code to generate the DOT files, and the output from neato (the same as dot, but for undirected graphs) is just as high quality.

Of course, as soon as I saw the output the cogs started moving in my mind... I'm now on a bit of a brainstorm on what can come next: How about ER diagrams generated from the database schema and published on an internal site. Generated documentation is never out of date, and it's a damn site easier having it generated of the fly than it is to load up Visio and get THAT monstrosity to do the job for you.

Anyway, the ER diagramming library will be open source, and it IS on its way... I promise.

(Note: if you want more info on dotty, take a look here)

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gonen said...

they use dotty

Rob Baillie said...

Looks pretty good, though I'm not keen on the look of the diagrams.

I get a feeling that there's a lot of people out there that have used Dot for this kind of thing. I don't think I'm exactly the first ;-)

Anyone else got any links to share?

Anonymous said...

Last year I developed a web application that displays PL/SQL call graphs (using both static code analysis and runtime data via dbms_trace). A conference paper is available via


If anyone's interested and has no access to the site above, I can also mail the paper (cn at gedv at)