Merge pull request #15 from qnikst/wiki/dev

wiki/dev updates.

Author: hyperthunk

wiki/development.md

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+---
+layout: wiki
+title: Development
+wiki: development
+---
+
+### Development
+
+This section contains topics that are under development and have not
+been formalized and added to formal specification or implemented.
+
+
+#### Registry specification
+
+*Problem: current specification doesn't cover the semantics of registry
+if the remote processes can be put into registry and if we can send 
+messages to such processes using `nsend`.*
+
+Here is a prosal for semantics that is summary of the [email thread](https://groups.google.com/forum/?hl=en-GB#!topic/cloud-haskell-developers/120_WugguPg)
+
+References are the following:
+
+  * Uni  - stands for unified semantics for Future Erlang
+
+  * Spec - stands for formal CH specification
+
+  * ML   - stands for mailing list
+
+**Semantics:**
+
+  1. Registry.
+      1. It should be possible to register remote processes in local registry (and local processes in remote registry)
+         Rationale: [Uni. Sec 2.3]
+
+      2. If a remote process is stored in registry then Node Controller starts monitoring that process
+         Rationale:  (Implicit requirement in because node should be able to receive notification about process death)
+
+      3. If a process dies and we get asynchronous notification then we remove process from registry
+         Rationale: [Uni. Definition 18, Uni. Table 12] 
+
+  2. `nsend` 
+
+      1. `nsend` should be implemented in terms of lower level function `whereis` and `send`
+
+      2. `nsend` is process does not exists in registry then message got silently dicarded.
+
+
+Possible problems:
+
+Current proposal opens space for race conditions, we should understand if those are relevant for us, and
+could or could not be solved
+  
+a. 2.1 adds a possibility for changing label beetwen where is and send, so message will be
+   sent to the wrong process.