[rfp-190] Initial commit (Resolve Java Modules)

rfps/rfp-0190-Resolve-Java-Modules.md

@@ -0,0 +1,78 @@
+# Resolve Java modules
+
+# Abstract
+Use the OSGi Resolver to assemble a self-contained OSGi application:  JRE + Framework + Bundles
+- A build/agent can call `jlink` on the resolved modules to make the JRE
+- A build/agent can setup an OSGi framework to boot with the resolved bundles
+
+# Use Case
+
+## Build a compact docker image
+
+## Build a compact self-contained command line tool
+- The users don't have to know it's java and maintain a compatible JRE 
+
+## Build a compact JRE
+
+- JPMS specifies that an external party has to select a consistent set of modules before calling it.
+- The OSGi Resolver can handle multiple versions and runtime requirements similar to a build.
+
+# Requirements
+
+## Req-1
+Must resolve OSGi bundles against Java modules without using the Java module identity
+- At least the Java module packages must be published under the `osgi.wiring.package` namespace
+
+## Req-2
+
+Must resolve Java modules against other Java modules and produce a valid set according to the JPMS restrictions
+
+- Module requires other module by ID
+- Modules may expose packages to a select set of friend modules
+- No two modules expose the same package
+- No cycles
+
+Or at least as many of these as possible
+
+## Req-3
+
+Should support version ranges on Java module requirements
+
+- Publish the module version set at compile time
+- Read the compile time versions of the module dependencies
+- Use heuristics to build a version range (possibly externally configurable)
+  - E.g. requirements for JDK modules have an open-ended version range: `[9, infinity)`
+  - E.g. requirements for use 
+
+## Req-4
+
+Should use as many of the existing namespaces as possible
+
+- Service Loader specification namespaces for the Java module services
+- `osgi.wiring.bundle` for Java module requirements
+- Prefer additional attributes on existing capabilities/requirements rather than new namespaces
+
+## Req-5
+May use bundle annotations on Java modules to handle dependencies that can not be captured by `module-info.java`
+
+ `@Target(ElementType.MODULE)`
+
+```
+@Requirement("(framework=jpa)(jpa.version >= 1)(!(jpa.version < 2))")
+module org.example.foo {
+    uses org.example.hello.Hello;
+}
+
+@Capability("framework=jpa", "version=1.0")
+module com.bar.jpa {
+}
+```
+## Req-6
+
+Must be able to resolve third party Java modules and expose their packages within the OSGi framework
+
+- At lest specify how `org.osgi.framework.packages.extra` should work
+
+## Req-7
+
+May specify runtime representation for the Java modules