Questions to kick off the IVOA Applications Messaging discussion

Questions

General

• Who should define messages?
• Which platforms/languages should be able to access the messaging system?
• Should the message router have any concept of the meaning of messages?

Intradesktop messaging

• Is publish-subscribe the correct model or should it be peer to peer?

...assuming yes:

PLASTIC

Compatibility

• Can your application send and receive messages via PLASTIC?
  • If not, what is missing?
• Could you embed a PLASTIC Hub in your application?
  • If not, what's stopping you?

Ease of use

• Should PLASTIC have more underlying transport protocols?
• Should PLASTIC have fewer underlying transport protocols?
• What would you change in the PLASTIC API?
• How do we deal with a multi Hub world?
  • Do we need a protocol for "handover" as one hub shuts down?
• PLASTIC supports request-response style and asynchronous messages. Are both styles necessary?

Power

• Is the PLASTIC model of a message as a simple string accompanied by arguments, with "method call"-like semantics adequate?

• Can PLASTIC cope with the widely different capabilities of different applications?

• How do we balance the need for messages to be general enough for max interop, with the specicifity needed to exploit the full power of an app?

General

• Do we need to be concerned with obsolescence of messages?

• Everything changes: How do we deal with versioning of the protocol?

• Do we need....?
  • Security?
    • How much?
  • Encryption?
  • Guaranteed delivery?
  • Guaranteed ordering?
  • Polling? (in PLASTIC messages are pushed to their recipients)

• Do we need to share access to data (rather than make copies)?
  • How?

• Should the system be dynamic (apps discover each other at runtime), or static (apps can be discovered even when not running?)
  • Is there/should there be a mechanism to start non-running apps?

Beyond the desktop

Client2Client

• Is there a demand for collaborative data exploration?
• What technologies are there that could facilitate this, and cope with firewalls, NATS etc?

Client2Server

• Is this any of our business or is this a GWS issue?

-- JohnTaylor - 01 Feb 2007