EPICS Channel Access EPICS Channel Access Version FourVersion Four

• Motivating FactorsMotivating Factors

• Solicitations from the audienceSolicitations from the audience

Motivating Factors - Data Motivating Factors - Data Size LimitsSize Limits

• Unlimited matrix boundsUnlimited matrix bounds

• Unlimited length stringsUnlimited length strings

• Do we fix the array size limit in Do we fix the array size limit in 3.14?3.14?

Motivating Factors - Motivating Factors - Extensible Data TypesExtensible Data Types

• Application defined “application” typesApplication defined “application” types– {units, limits, application specific attributes}{units, limits, application specific attributes}

• Application defined container typesApplication defined container types– Message passingMessage passing

– Command completionCommand completion

• GDD already provides this functionalityGDD already provides this functionality– CA protocol currently does notCA protocol currently does not

Motivating Factors - Motivating Factors - Matrix DataMatrix Data

• Client discovers N dimensional Client discovers N dimensional bounds of databounds of data

• Client addresses any hyper cube Client addresses any hyper cube within boundswithin bounds

Motivating Factors - Motivating Factors - Monitoring DataMonitoring Data

• Application adjustment of monitor Application adjustment of monitor queue lengthqueue length

• Periodic monitorsPeriodic monitors– Less network traffic than periodic getsLess network traffic than periodic gets

Motivating Factors - Motivating Factors - Monitoring DataMonitoring Data

• Application defined event typesApplication defined event types– Servers post RF arch down eventsServers post RF arch down events

– Clients monitor for RF arch down Clients monitor for RF arch down events when POWER>10KWevents when POWER>10KW

– Data acquisitionData acquisition

Motivating Factors - Motivating Factors - Improved APIImproved API

• Simplified C++ client API is easier to Simplified C++ client API is easier to extendextend and use and use

• Client API exports full functionality Client API exports full functionality currently in the server APIcurrently in the server API

• Eliminate vxWorks “task variables” Eliminate vxWorks “task variables” from client libraryfrom client library

Motivating Factors - Motivating Factors - Directory Service 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 Directory service tells clients that resource has movedresource has moved– Directory service equivalent of beaconsDirectory service equivalent of beacons

Motivating Factors Motivating Factors

• Compact protocol is more efficientCompact protocol is more efficient

• Multi-priority clientsMulti-priority clients

• Attempts to create two channels Attempts to create two channels with the same name returns first with the same name returns first channel createdchannel created

Is GDD in Our Future?Is GDD in Our Future?

• Reuse one data descriptor for many Reuse one data descriptor for many data instances? GDD requires one for data instances? GDD requires one for eacheach

• Is GDD complexity daunting?Is GDD complexity daunting?

• Is a C++ abstract base class (function Is a C++ abstract base class (function jump table) a more flexible data jump table) a more flexible data description mechanism for this API?description mechanism for this API?

Solicitations From the Solicitations From the AudienceAudience