Bob Jacobsen August 6 Informal discussion of BaBar software BaBar offline code’s ecological niche Set of non-overlapping idioms Event - our software bus? Manages ownership of all common data Provides access by name & type Rendesvous is outside the software, among the people Not all Tracks are really alike, and those differences can matter Environment - slower changes, common config/conditions Blind request via proxy cache-handlers Writing the proxies was tricker than anticipated Significant update computation built in by systems Used by non-overlapping “modules” Simple inherited interface Not strongly typed!

Bob Jacobsen August 6 Informal discussion of BaBar software Execution & Configuration Idiom “What to execute” mixes two levels Sequence of modules Specific settings in those modules Configuration via “Framework” tool TCL & command line Several forms Now using “execute scripts” plus “dump&restore” Execution (event loop, start/stop, etc) via same tool Multiple implementations to handle specific event sources Visible in the event loop implementations, start/stop, error handling

Bob Jacobsen August 6 Informal discussion of BaBar software Components == Modules? Most composition is of small algorithms E.g. a track finder, an alignment processor, etc This is where variation happens Much more often than “a new histogrammer” Much more necessary Composition by coding vs composition by configuration

Bob Jacobsen August 6 Informal discussion of BaBar software Application building vs exploration We have >100 “production” applications Routinely built, run past author’s end of interest Alignment, QA, etc Plus 100’s of “analysis” executables Built by composition of modules Getting it to link, run is not hard Hard questions: What components are needed? How exactly should they be configured? E.g. “run at all” vs “give right answer”

Bob Jacobsen August 6 Informal discussion of BaBar software Configuration Configuration management via releases Configuration sanity checking? Distribution of knowledge Computer vs human reasoning

Bob Jacobsen August 6 Informal discussion of BaBar software Role of general knowledge We didn’t actually speak FORTRAN… C++ from books, other labs, vs local idioms “Burden of proof” approach by collaborators