1. EPICS Channel Access Version Four Motivating FactorsMotivating Factors Solicitations from the audienceSolicitations from the audience

2. Motivating Factors - Data Size Limits Unlimited matrix boundsUnlimited matrix bounds Unlimited length stringsUnlimited length strings Do we fix the array size limit in 3.14?Do we fix the array size limit in 3.14?

3. Motivating Factors - Extensible Data Types Application defined “application” typesApplication defined “application” types –{units, limits, application specific attributes} Application defined container typesApplication defined container types –Message passing –Command completion GDD already provides this functionalityGDD already provides this functionality –CA protocol currently does not

4. Motivating Factors - Matrix Data Client discovers N dimensional bounds of dataClient discovers N dimensional bounds of data Client addresses any hyper cube within boundsClient addresses any hyper cube within bounds

5. Motivating Factors - Monitoring Data Application adjustment of monitor queue lengthApplication adjustment of monitor queue length Periodic monitorsPeriodic monitors –Less network traffic than periodic gets

6. Motivating Factors - Monitoring Data Application defined event typesApplication defined event types –Servers post RF arch down events –Clients monitor for RF arch down events when POWER>10KW –Data acquisition

7. Motivating Factors - Improved API Simplified C++ client API is easier to extend and useSimplified C++ client API is easier to extend and use Client API exports full functionality currently in the server APIClient API exports full functionality currently in the server API Eliminate vxWorks “task variables” from client libraryEliminate vxWorks “task variables” from client library

8. Motivating Factors - Directory Service Directory service client side plug insDirectory service client side plug ins Server updates directory serviceServer updates directory service Directory service tells clients that resource has movedDirectory service tells clients that resource has moved –Directory service equivalent of beacons

9. Motivating Factors Compact protocol is more efficientCompact protocol is more efficient Multi-priority clientsMulti-priority clients Attempts to create two channels with the same name returns first channel createdAttempts to create two channels with the same name returns first channel created

10. Is GDD in Our Future? Reuse one data descriptor for many data instances? GDD requires one for eachReuse one data descriptor for many data instances? GDD requires one for each Is GDD complexity daunting?Is GDD complexity daunting? Is a C++ abstract base class (function jump table) a more flexible data description mechanism for this API?Is a C++ abstract base class (function jump table) a more flexible data description mechanism for this API?

11. Solicitations From the Audience