The Hogg Blog : PDC2008

Oslo MGrammar Turtle Graphics for VS2008

Jason Hogg — Sat, 13 Dec 2008 04:16:00 GMT

My colleague Joshy Joseph reminded me that the MGrammar based Turtle Graphics parser that I posted here was for VS2010. I have attached a newer version of the solution that Joshy coverted to run in VS2008. I noticed that Doug Finke has also done the same thing whilst also creating a couple of additional samples as well. Take a look at his blog for more details...

Creating a Logo / Turtle Graphics Textual DSL using Oslo MGrammar

Jason Hogg — Wed, 26 Nov 2008 01:17:00 GMT

In the early 1980's a programming language called Turtle Graphics was used as a means of introducing novices to programming on the BBC Microcomputer. Turtle graphics, a graphical version of Logo, helped introduce people to programming using a simple functional language that provided instant visual gratification allowing the user to move a triangular turtle across the screen using simple commands such as forward, backward, right turn and left turn.

At PDC this year the Connected Systems team introduced a new language called "M" - which allows textual DSL's to be created. I will talk more about this language in future posts especially compared with the F# Lexer and Parser that we used to create our textual DSL for SecPAL, but first I wanted to create a programming language with which to learn Mg. I thought a version of Turtle Graphics would be fun - and interesting for anyone else interested in experimenting with or learning Mg.

The programming language I am liberally calling Logo (and the associated interpreter) are fairly simple - but I thought it would be fun for people to play with, especially those with children who are looking for new ways to introduce their kids to progamming. I did the bulk of the work specifying the grammar for this simple version of Logo on the flight back from LA to Seattle - which should give you a sense of how intuitive Mg is - and how productive the Intellipad authoring experience is.

Given that Thanksgiving is just two days away I figured it would be patriotic (odd coming from an Aussie/Kiwi/Pom hybrid) to show how simple it is for this language to draw the United States flag - a design which obviously would make significant use of loops and nested loops.

The screenshot above shows the output from this program. The complete logo program listing is also included below so you can see how complex objects can be created using a simple grammar comprising of just 5 commands:

    - Commands - Commands perform actions such as moving or rotating.
        Rotate n - Rotate 'n' degrees
        Draw n - Draw a line 'n' pixels long
        MoveAbs x, y - Move to an absolute position
        Move x,y - Move to a position relative to last move / draw command
    - Loops - Sets of instructions which are executde iteratively. Loops can be nested.
        Loop n { [Command] }*

I have attached the full source code for this so that you can play with this yourself. The source code is based on the PDC (October?) version of Oslo which you will have to first download from MSDN. The language could easily be extended to include color, line widths, other types of lines such as bezier curves etc - which should provide a good introduction for anyone interested. Post pointers if you do anything fun with this.

In addition to the formal grammar for my logo language (logo.mg) the .zip file also includes a WPF interpreter that interprets the parsed output of our logo programs and converts them into WPF Path Geometry syntax. There is also a simple editor that allows you to edit and run our Logo programs - providing a nice easy way to start teaching your children to program. Or for yourself to start modifying the language as described above.

Enjoy!!! And (to those in America) Happy Thanksgiving...

// Logo (and Mg) sample program
// Happy Thanksgiving!

// Move to top left
MoveAbs 25,25

// Draw five rows of stars
Loop 5
{
   // Draw ten columns of stars
   Loop 10
   {
   // Draw five points to make each star
   Loop 5
   {
         Rotate -54
         Draw 5
         Rotate 126
         Draw 5
   }
   Move 20 -1
   }
   Move -210,20
}

// Draw the lines next to the stars
MoveAbs 430,25
Rotate -90
Loop 5
{
   // Lines are 5 pixels high
   Loop 5
   {
      Draw 200
      Move 200,1
   }
   Move 0 15
}

// Draw the lower lines on the flag
MoveAbs 430,125
Loop 5
{
   // Lines are 5 pixels high
   Loop 5
   {
      Draw 410
      Move 410,1
   }
   Move 0,15
}

Geneva Identity Management Framework

Jason Hogg — Mon, 27 Oct 2008 22:08:00 GMT

For anyone who has followed my blogs around developing an STS or writing authorization policies you will be very interested in Kim Cameron's announcement at PDC of the Geneva Identity Management platform. Genvea includes:

Geneva Framework - A .NET framework for writing interoperable, claims aware applicatoins
Geneva STS - An STS integrated with AD. Supports issuance (finally) and consumption of Cardspace Cards.
CardSpace Geneva - A federation client

In addition to these framework like components, there are also a couple of services (biult using Geneva) including:

Microsoft Federation Gateway - Provides the basis for the Microsoft Services Identity backbone - brokering access to Microsoft cloud applications and developre services
Microsoft Connector Services - Federates AD to the Microsoft Federation Gateway. Provides lightweight access to the federation gateway.
.NET Access Control Service - Next generation service (STS) that performs claims transformation. It receives authentication information and issues authz decisions. This includes a management portal and API's for managing and writing authz policies.

I haven't had a chance to play with any of these tools yet, but will be very interested to see how the Access Control Service's capabilities compare with SecPAL... :-)

Microsoft Azure cloud OS announced at PDC2008

Jason Hogg — Mon, 27 Oct 2008 20:51:00 GMT

I am here at the PDC in Los Angeles having just watched Ray Ozzie and Bob Muglia finally present the next generation of Microsoft's Cloud Services / Software plus Services strategy with the release of our new operating system for the cloud "Azure"!

Windows Azure was designed from the ground up for the needs of cloud based computing models. It includes capabilities such as:

Scalable hosting - from a fraction of a server to many servers
Automated service management - fabric controller manages the health and lifetime of deployed services according to a services model
High-availability - replicated backend storage
Rich developer experience
Open platform - Command line interfaces, REST protocols, WS, Web…

As I watched the presentation it dawned on me some of the parallels between how existing operating systms are designed and the functions that will now be fulfilled by Azure. The diagram below shows a conceptual view of the core layers in existing operating systems, which are typically split between kernel mode and user mode where user applications are designed to be run.

Logically Azure follows a similar model having the Azure OS providing the equivalent of the kernel exept now running in the cloud managing a potentially limitless number of CPU's, memory and disk storage all hosted in the cloud.

Moving up a level we have the Microsoft Azure Services Platform. As with the executive in an OS taking responsibility for security, storage, I/O and IPC; Azure provides a host of similar capabilities. At the lowest level the Azure Services Platform includes support for .Net Services including a Service Bus, Access Control and Workflow Services. It also includes SQL Services. At a higher level the Azure Services Platform includes support for Live Services, Sharepoint Services and Dynamics CRM Services.

In terms of how applications can be designed to run on in this new cloud based paradigm the great news is that it is all through our existing tools and languages - Visual Studio and .NET. At the highest level in the stack where traditionally applications like Office would run, we now have online extensions to these products including: Windows Live, Office Live, Exchange Online, Sharepoint Online and Dynamics CRM Online.

Anyway, this post should introduce you to some key concepts and technologies that I believe are going to be critical to consider as you design distributed applications moving forward. I personally think this announcement and the associated announcements that you will continue to hear over the course of this week is the most significant change in our industry since the release of .NET.