Entering numbers: the computer science of the everyday Dr Paul Cairns Reader in Human-Computer Interaction CS Open Day, Paul Cairns129th September, 2012

Aims ▪Computer Science of Everyday Things −Number entry −Regular expressions −Human-computer interaction ▪A taste of things to come CS Open Day, Paul Cairns229th September, 2012

Number entry CS Open Day, Paul Cairns329th September, 2012

To err is human… ▪Very common device in NHS ▪Nurse entered 68 not 6.8 ▪Patient died next day ▪What actually happened? 29th September, 2012CS Open Day, Paul Cairns4

But it’s very rare, isn’t it? ▪People make mistakes −10% of all admissions −10% of those are potentially fatal −40,000 per year in the US ▪Human error or poor design? 29th September, 2012CS Open Day, Paul Cairns5

Thinking about numbers ▪Think up 5 different numbers that plausibly you might enter into a syringe pump? −Concentrations −Volumes −Times −Rates ▪Explore the possibilities 29th September, 2012CS Open Day, Paul Cairns6

ISMP Guidelines ▪No trailing zeros (5 mg, never 5.0 mg) ▪Use leading zeros for doses less than one measurement unit (0.3 mg, never.3 mg) ▪Units ▪Font: th September, 2012CS Open Day, Paul Cairns7

Regular expressions ▪Shorthand ▪Describe “strings” of characters ▪Three operations: −Sequence −Iteration, * −Optionality, | 29th September, 2012CS Open Day, Paul Cairns8

Examples ▪Let = “A”|… |“Z” ▪Num = “0”| … |“9” ▪LetLet NumNum LetLetLet ▪“Y” Num* 29th September, 2012CS Open Day, Paul Cairns9

Exercise ▪Can you come up with a regular expression for ISMP compatible numbers? 29th September, 2012CS Open Day, Paul Cairns10

RE and Syringe Pumps ▪Use RE to block invalid numbers ▪Exhaustive simulation of errors −Java, Mathematica ▪Halve the out-by-10 errors 29th September, 2012CS Open Day, Paul Cairns11

RE and Syringe Pumps ▪Use RE to block invalid numbers ▪Exhaustive simulation of errors −Java, Mathematica ▪Halve the out-by-10 errors ▪But we had to guess some bits 29th September, 2012CS Open Day, Paul Cairns12

Computer Science could help… ▪Device logs ▪Regular expressions ▪Simulations ▪Interface design 29th September, 2012CS Open Day, Paul Cairns13

Where to find out more ▪ ▪Norman, Design of Everyday Things ▪Here CS Open Day, Paul Cairns1429th September, 2012