DSL with fixed ports per element   

I'm looking to model data processing - with data sources, sinks, processors 
(both a sink & source) and a few more complex components (e.g. a quality 
filter which has a normal output and a "rejects" output).  Not the most 
original of problems, probably been invented 10 times already somewhere...

Anyway, I was looking at the options on how to do this under the VS 2008 DSL 
system, and tending towards the components/ports template as a starting point 
- having those complex components means more than one connector to/from the 
shape and so I need to logically distinguish them with a source/target port.  
I am having trouble working out how best to fix the number and type of ports 
for each element.  I think I could do a rule to fire upon adding elements to 
the model that quickly also adds the necessary ports, and ban all other 
additions/deletions, but it sounds kludgy.

I'd also like to fix the port's name to be derived from it's parent element 
- i.e. if that was a "SourceWidget1" then I'd like it's OutPort to be a 
"SourceWidget1_Output" (given I think it still needs to be unique and so 
can't be just "Output").  To maintain this during renaming, is it best again 
to create a rule to monitor changes to Names and fixup?

date: Tue, 22 Jul 2008 07:15:01 -0700   author:   Tristan MSDN Keen

RE: DSL with fixed ports per element   

To answer my own questions for anyone else coming across this:

  To have toolbox components come with a pre-defined list of ports, override 
CreateElementToolPrototype in <YourDSL>ToolboxHelper to create new 
ElementGroup Prototypes.  The "Domain-Specific Development with Visual Studio 
DSL Tools" has a good explanation in their book & Circuits example - buy it!

  Then you need to block deletion of the ports - which don't need any 
special naming, BTW.  This could be done by rule or OnDeleting, but throwing 
an exception is a bad "user experience" and blocking the delete option at the 
GUI is seen as better.  Easiest way to do this is using the JaDal library at 
http://www.codeplex.com/JaDAL. 

Tristan.

"Tristan MSDN Keen" wrote:

> I'm looking to model data processing - with data sources, sinks, processors 
> (both a sink & source) and a few more complex components (e.g. a quality 
> filter which has a normal output and a "rejects" output).  Not the most 
> original of problems, probably been invented 10 times already somewhere...
> 
> Anyway, I was looking at the options on how to do this under the VS 2008 DSL 
> system, and tending towards the components/ports template as a starting point 
> - having those complex components means more than one connector to/from the 
> shape and so I need to logically distinguish them with a source/target port.  
> I am having trouble working out how best to fix the number and type of ports 
> for each element.  I think I could do a rule to fire upon adding elements to 
> the model that quickly also adds the necessary ports, and ban all other 
> additions/deletions, but it sounds kludgy.
> 
> I'd also like to fix the port's name to be derived from it's parent element 
> - i.e. if that was a "SourceWidget1" then I'd like it's OutPort to be a 
> "SourceWidget1_Output" (given I think it still needs to be unique and so 
> can't be just "Output").  To maintain this during renaming, is it best again 
> to create a rule to monitor changes to Names and fixup?

date: Tue, 5 Aug 2008 01:28:11 -0700   author:   Tristan MSDN Keen am