Best PDC session so far : Lap around “Oslo”

I’m at the “Lap around ‘Oslo’” talk together with Alex Thissen and Paul Gielens. This is by far the best session I’ve seen so far!

The talk began about models. We were looking at modeling and modeling domains, but what is a model? We have…

  • Drawings
    Models used to communicate with others, for example DataFlow or Use Case. See UML as Sketch.
  • Model-Assisted
    Models used to understand or manipulate code, for example StaticStructure or Sequence
  • Model-Driven
    Models executed by runtimes directly, for example HTML, CSS, XAML, BPEL

According to Douglas Purdy, Don Box says we’re on a 30 year journey and we’re 15 years in. We had COM(+), .NET 1.0, Web Services, .NET 3.0 and now we’re entering the next phase. Oslo is the next level for a model-driven platform. We’ve been heading there via configuration, attributes and doing more and more declarative instead of typing everything out. A great example for declarative development is of course LINQ.

Why is this happening? Transparency (better understand your application), flexibility (add changes to your application faster) and productivity. We need models

So what is Oslo?
It is the platform for model-driven development. Microsoft will bring us Oslo with the following components:

  • “M”
    The language for authoring models & DSLs
  • “Quadrant”
    The tool for interacting with models & DSLs
  • Repository
    The database for storing & sharing models, this will be SQL Server.

“M” gives you the modelling and textual DSLs. According to Douglas Purdy and to Don Box, this is going to be the next big thing. I could not agree more. I am SO excited about what I just saw. Take the example they’ve shown.

Module Microsoft.Samples


  // MusicItem is the schema

  type MusicItem


    // Primary key

    Id : Integer64 = AutoNumber();

    Album : Text; // Album is constraint by type

    Artist : Text;

    // Rating is constraint and expression

    Rating : Integer32 where value <= 3;

  } where identity Id;


  // * is 0..n multiplicity

  MusicLibrary : MusicItem*;


The above declares a schema named “MusicItem” and a collection of those in a “MusicLibrary”. We compile this and than populate the result in the database.

// M compiler

// Repository is the database. When choosing -t:xml we generate XML

m.exe myfile.m /p:image -t:Repository

// Populating

mx.exe / /db:repository /ig /f

mx uses the compiled “binary” (this is a zip archive actually) and generates T-SQL.

create table [Microsoft.Samples].[MusicLibrary]


  — the rest


You can fill the database with the following

Module Microsoft.Samples





      Album = "Slippery when wet",

      Artitst = "Bon Jovi",

      Rating = 3



      Album = "Into the dark",

      Artitst = "Europe",

      Rating = 2




This creates two rows in the table MusicLibrary. But this is all the language “M”. How about a textual DSL? How’s this for coding:

"SomeAlbum" by "Led Zeppelin" is awesome!

"Back in Black" by "AC/DC" is so so.

"Bad" by "Michael Jackson" is terrible.

The above code can be transformed into the exact same code-block as above, where we filled the database with two records. How is this achieved? Take a look at the following code.

module Microsoft.Samples


  import Language;


  language MusicLibraryLanguage


    syntax Main = s:Statement+ => MusicLibrary(valuesof(s){l


    syntax Statement = al:Grammar.TextLiteral "by" ar:Gramar.TextLiteral "is" ?????

    => { Album {al}, Artist {ar}, Rating


    @{(Classification["keyworkd"]} // colorize "awful"

    token Rating1 = "terrible" | "awful";

    token Rating2 = "so so";

    token Rating3 = "awesome";


    syntax Rating = Rating1 => 1 | Rating2 => 2 | Rating3 => 3;


    interleave skippable = Base.Whitespace



I lost the code where it says “????”. The above code tells to look at by and is and takes the text there and parse it. It than looks at the rating and gives it an actual number. The Classification keyword makes the words “terrible” and “awful” become bold in the editor.

Now is this awesome or what? I’m so excited by this. This is one of the biggest steps in my history of developing software. You can now write code like

Give me a table called “Customers” with a primary key called “Id” and make it an integer with identity on, seeding from 1.

The best thing is, if you can think of a way to make that sentence shorter or more self-explaining, go ahead! Use MGrammer to define your own textual DSL.

Another great demo was when they showed MService. With only a few lines of code (my battery ran flat, so I could not copy the code, but I photographed it and it will come in this blog!) they created a WCF service where they could upload an image and request it again, using a WF workflow. In about 38 lines of code, { and } on empty lines included!!!

Courtesy of Paul Gielens, I got the code from his weblog. The following starts a REST enabled WCF Service with a WF Writeline activity. Not a Console.Writeline, but a real WF activity.

module Service25


  service Service


    operation Echo(str : text) : Text


      .UriTemplate = "echo/{str}";

      WriteLine { Text = "Message : " + str }

      return str;




At first I thought this was an awesome code generator. But boy was I wrong. They showed debugging and hitting breakpoints inside the textual DSL!!! The stack and locals windows showed the WCF channels and WF activities active. Can you believe it? Probably not, you just have to watch the stream on Channel9.

I’m now going to follow Don Box, hold on for more!

Loving it, loving it, loving it, as Don Box would say!

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5 Responses

  1. Colin Jack says:

    One thing I’m struggling to understand is what you do if MusicItem is to contain behavior, how do you factor that in?

  2. Dennis van der Stelt says:

    One thing I’m struggling to understand is how you’d build a full application with this. I’ve asked it to people from the Oslo team (can’t remember the name) but everyone evades the answer. As if they did not think of this. Weird.

    In the MService post however ( you can see how behavior is inserted into the model. My responding question would be, how to insert this using Quadrant… Probably some custom views with the appropriate properties.

    It’s only a few weeks after PDC, I’ve thought some stuff over and have many, many, MANY more questions than initially at the PDC.

  3. Colin Jack says:

    Its interesting that the REST example uses the language “service” and “operation”.

  4. Dennis van der Stelt says:

    @Colin : Because? Check out the following link btw for more MService code.

  5. I guess that to get the from banks you should present a firm reason. But, once I’ve got a sba loan, because I was willing to buy a bike.

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