Had lunch with Bill today (which is fun, BTW; everyone should do it). It turns out that our separate food acquisition efforts demonstrate the difference between synchronous/sequential and asynchronous/concurrent processing.
(My apologies to readers who either never go to restaurants or only eat at tableservice restaurants. You may need a fast food patron to explain this analogy.)
Bill likes burritos from Moe's Southwest Grill, whereas I like a soup-and-sandwich from Panera Bread. So sometimes we each get lunch from our preferred place, then meet at a shared table. I keep getting to the table first; Panera is faster. (Sorry Moe's; don't shoot the messenger.) This may in part be because sandwiches are faster to make than burritos, but that can't be the whole explanation.
A large part of Panera's advantage is that its process is asynchronous and concurrent. (Bill made this observation before I did.) You order and pay at one counter (several registers, a pooled resource), then asynchronously receive your sandwich at a separate counter (they call your name as a correlation ID). They make your sandwich while you're paying and getting a drink (concurrent processing). Moe's, OTOH, uses a sequential process: They line everyone up single file, where you lockstep place your order, follow your food as they prepare it, pay for it at the single register, then get your drink. So one person who takes longer than usual to order or pay holds up the whole line.
Not to pick on any one restaurant franchise: Subway is sequential, Schlotzsky's Deli is asynchronous and concurrent. The fast food granddaddy, McDonald's, (which some of my Australian friends refer to as "the American Embassy" (not these)) is a mix: The food is prepared concurrently, but you still stand at the register, often blocking the patron behind you; kind of a pseudo-synchronous call. Burger King's single register is more sequential than McDonald's register pool, but its delivery-by-number is asynchronous whereas McDonald's order-taker-gets-food delivery is synchronous.
(BTW, for a real horror movie, skip The Amityville Horror and The Texas Chainsaw Massacre and see Super Size Me, or read Fast Food Nation. BTW, the NRA's (the National Restaurant Association, not the gun people) review of the book: Hated it!)
Moe's moves noticeably slower than Panera, and I think the sequential nature of Moe's workflow has a lot to do with it. Check it out at the next fast-serve, get-your-food-at-the-counter-before-finding-a-table restaurant you go to. Asynchronous-and-concurrent wins again!
(Disclaimer: This blog posting does not constitute an official endorsement by IBM Corp. for or against any of the restaurants named. To this author's knowledge, said information technologies company has not acquired any of the named franchisers.)
JMS: Synchronous and Sequential vs. Asynchronous and Concurrent