[INFOD-WG] Implementation Issues.

[Vijay Dialani]

Hi All,

When helping Raghul with implementation issues, three questions were 
raised from his side:
1. Implementation and use of Dynamic Constraints (Status: solved)
2. How does the publish messages (with TTL) as it become aware of that new 
dynamic consumers? (Status: solved)
3. How does publisher handle frequent notifications about consumers? 
(Status: Unsolved)

For the first issue, I found that the specification is ambiguous, in some 
section it requires consumer to handle the Dynamic Constraints, in some 
other sections it requires publishers to handle the Dynamic Constraints. 
Attached are the text excerpts from the base specification:


>From section 1.1.1
In addition a subscription may include dynamic consumer constraints. These 
are constraints which are evaluated by the consumer rather than the 
registry by looking at the contents of a potential message.
>From Glossary
Constraint      Constraints are used to specify which conditions must be 
satisfied to be eligible for an interaction. Constraints must be 
formulated in the constraint language(s) that are associated to the 
vocabularies, which are used to structure the referenced data. Most 
constraints are evaluated by the registry but dynamic consumer constraints 
are dealt with by the consumer. The absence of constraints shows that the 
interaction is unrestricted.

>From section 2.4.1 and section 2.4.2

These Constraints are designed to determine the consumers of each message 
based on its content; i.e., a Dynamic Consumer Constraint cannot be 
applied by the INFOD registry and is processed by the publishers. 

This clearly show inconsistency in the specification. We assume that the 
DynamicConsumerConstraints need to be evaluated by the publisher and will 
like to know uses cases for evaluation by consumer, if any.

The dynamic consumer constraints will be based on data vocabulary and we 
are working on actual mechanisms for implementation,

Second, issue:
The Publisher internally associated TTL with every message and retains 
them as its internal state. When it receives the notification about a new 
consumer, it examines the internal queue of messages and notifies the 
consumer in appropriate order.

Third issue:
We will be seeking help from Oracle team to help with DB internals  and 
choice of appropriate indexing mechanism.


Regards,
Vijay Dialani, Ph.D.
IBM Almaden Research Center, B2-237
650 Harry Road
San Jose, CA 95120 USA
Email; vdialani at us.ibm.com
Phone: 408-927-1406 Tie line: 457-1406
Fax: 408-927-1780

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