[teiid-dev] VDB metadata consumed by Teiid

[Alex Miller]

> > Did you guys kill off the command-line vdb tool?  Seems like that was one 
> possible direction for importing physical metadata and potentially to add views 
> within a lightweight tool.
> 
> We could still go this direction, except for a) it's not really that 
> lightweight, b) it does nothing to allow for integration with metadata from 
> other products, and c) I don't believe it even supported views, just access to 
> multiple physical sources.

a) true (although it was lighter weight than the designer), 
b) true although it would be theoretically possible to create an infrastructure to import metadata through some sort of combined connector/metadata importer infrastructure that we always talked about 
c) correct, although a relational view can almost entirely be defined by the view sql statement.  view definition was in the original design work.  other views (like xml) are far more complicated and not amenable to a command-like interface, imho.  a dsl benefits from being able to be command-like for simple stuff and a declarative definition for hairy stuff so it can scale better (although it's easy to do dsls badly as well).

I'm not really arguing for or against any of these, just brainstorming.  The benefits of a command driven tool are that it frees you from committing to anything other than the commands (and not vdb formats or definition languages).
 
> > Another possibly crazy idea that I would seriously consider these days is 
> using an embedded dsl / builder in a language like Groovy to define vdb 
> metadata.  You could take the groovy script itself as the vdb definition or even 
> run it to produce a compiled vdb.  If you were clever enough, the dsl could be 
> extensible to allow metadata creation with new metamodels.  But this is probably 
> only a valid solution if you expect a developer or other suitably precise user 
> to be the target.
> 
> 
> I believe the developer audience you mentioned is a serious concern, and as with 
> your first suggestion, this also provides no type of standard with which to 
> leverage any sort of interoperability with other products.

Extensible dsls would allow you or others to build plugins that could take DDL or whatever format is appropriate.

One way to think about this problem is to what you want to nail down and live with and what you want to allow to change in the future.  Depending on your roadmap, you would make different decisions.  Some things you might want to lock down:
- commands in a tool
- vdb format -> currently this is locked down binary archive and is highly structured and opaque
- a language describing the contents of a vdb - "language" could be SQL or some other more flexible DSL 
- an api 

I suspect that to foster a community, whatever choice you make would be served by having a pluggable way to add new metadata.  Seems like that's where you started from in the original email.