More on consuming models
A set of interesting questions were posted to the DSL Tools Newsgroup recently, so I've decided to reply to them here. The text from the newsgroup posting appears like this.
Hello -- I quickly ran through the walkthroughs and worked a little with the beta version of your tools, and they are neat. Having designed a modeling language and build a few models, one thing which I would like to do is 'execute' those models. I want to write a C# plugin for Visual Studio which uses an automatically-generated domain-specific API to query and perhaps modify the models programmatically. Based on what the plugin finds in the models, it can do some other useful work. Let's say I want to do some domain-specific analysis, where there isn't any existing analysis framework which correctly supports my domain. In that case, I might as well roll my own analysis framework as a plug-in which is integrated with VS's DSL tools. What I don't want to do is serialize the models to XML and have my independent tool read in the XML file, create an internal representation of the models in memory, and then do stuff. It's a waste of time. I want to integrate my analysis tool with VS and access my models...directly.
These are exactly the kinds of scenario we are envisaging. As I discussed in a past entry, creating models is not much use if it's difficult or impossible for other tools to consume them.
So, my hope is:
- that VS is storing the models in memory in some kind of repository where my plugin can get at them quickly, and
- that the repository exposes both domain-specific and generic hooks for CRUD operations on my models, and
- there is some way for me to write a plug-in which can integrate with VS to create an integrated domain modeling environment. Sort of like using VS as the foundation for my own domain-specific modeling tool.
Will this be supported? If so, can you publish a walkthrough about this? The models are only worth so much if they're only good for xml/text/code generation --software isn't the only thing which needs to be modeled.
The models are held in memory (we call it the in-memory store). As well as giving access to CRUD operations, this supports transactional processing and event firing. We also generate domain specific APIs from domain models - indeed, you can see what these APIs look like if you look at e.g. XXXX.dmd.cs generated from the XXXX.dmd using the template XXXX.dmd.mdfomt in a designer solution. These APIs work against the generic framework, thus allowing both generic and domain specific access to model data. However, we still have some work to do to make all this easily available, including making some improvements to the generic APIs and doing some repackaging of code. The goal would be that you'd be able to use the dll generated from a domain model to load models into memory from XML files, access them through generic and and domain specific APIs, and then save them back to XML files. We will also be overhauling the XML serialization, so that models will get stored in domain specific, customized XML - see Gareth's posting for some details around this.
As for VS plugins, these will be supported in some way, for example via the addition of custom menus to your designer, or by writing 'standalone' tools integrated into VS making use of the existing VS extensibility features.
On the issue of timing, the API work will happen over the next few months, the serialization work after that. We will continue to put out new preview releases as new features are introduced. Walkthroughs, other documentation and samples will be provided with the new features.