[jsr294-modularity-eg] 294 EG F2F meeting, 2009-03-23

[Alex Buckley]

// EG members, feel free to add/edit points I haven't noted correctly.


* Attendees

Alex Buckley, Bryan Atsatt, Richard Hall, BJ Hargrave, Peter Kriens,
  Sam Pullara, Bob Lee (standing in for Michal Cierniak; Bob has now
  joined the EG as a second Google representative)
Apologies: Daniel Leuck


* Module grouping

Bryan phrased a key requirement (supported by most EG members) as: 
multiple modules can cooperate using types not available to outsiders. 
This means multiple modules can ACCESS each others' types which remain 
INACCESSIBLE from other modules. A module system would necessarily have 
to make the types visible across modules as well.

BJ blogged an excellent summary of visibility v. accessibility:
http://blog.bjhargrave.com/2009/03/i-am-visible-but-am-i-accessible.html

The meeting decided to stay with 'runtime module' as the sole mechanism 
by which a module system can group multiple modules.

The meeting decided not to adopt a 'module scope' concept, or module 
nesting, for grouping multiple modules.

Access control can implicitly be deferred to the module system by having 
the VM call Module.hasModuleAccess(Module m) when computing 
accessibility to a module's types. (The receiver is the requested 
module.) A Module can return this==m in simple cases, or simulate more 
advanced concepts like nesting.

The meeting discussed a permission check allowing a client to use a 
classloader to define a class *as a member of a given runtime module*. 
However, since the client is likely to be a module system and must 
already have permission to get the classloader, a new permission was 
seen as low priority.


* Compile-time use of a module system

Most EG members do not support declaring dependencies (i.e. controlling 
visibility, also called observability in the JLS) with a keyword in Java 
source code. Sam and Bob proposed declaring dependencies with 
annotations, though that has bootstrapping issues.


* Next meeting

Wednesday 1 April. 10am US West, 1pm US East.

- Compile-time use of a module system, especially in light of the
   OSGi Tool Summit:
   http://eclipsesource.com/blogs/2009/03/31/osgi-tool-summit-recap/


Alex