Reading. Devices. Graph Theory. Press On, Chapter 8 A city is not a tree. States Actions. Push. Invented by Euler in 1736 Hence, Euler tour

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1 Reading Devices Press On, Chapter 8 A city is not a tree Christopher Alexander, Design, No 206, February 1966, pp46-55 States Actions Off Push On Graph Theory Invented by Euler in 1736 Hence, Euler tour Push Four Colour Theorem Stated 1852 Proved 1976 controversially

2 A graph is (roughly) Vertices Edges or Arcs Vertex labels Vertices Arcs (edges) Labels for arcs and vertices Arc labels

3 Graphs and interaction Vertices = states Arcs = transitions or actions Graphs don t run as such FSMs run Trivial? Cutting-edge research? Practical? undirected multigraph V(G)=4 E(G)=7 Non Eulerian Example graphs Web, transition systems, statecharts, user manuals, maps, cities, computer networks, road systems, telephones, games, genealogies, neural networks, electrical circuits, food cycles, metabolic cycles, games, buildings Data structures Trees, lists, hash tables, object hierarchies

4 Vertex, state, node, mode Label Vertex, state, node, mode Arc, transition, edge, arrow, function, update Label Arc, transition, edge, arrow, action, function, update T Institute for Safe Medication Practices ISMP slist of Error-Prone Abbreviations, Symbols,andDose Designations he abbreviations, symbols, and dose designations found in this table The Joint Commission (TJC) has established a National Patient have been reported to ISMP through the USP-ISMP Medication Safety Goal that specifies that certain abbreviations must appear on Error Reporting Program as being frequently misinterpreted and an accredited organization's do-not-use list; we have highlighted these involved in harmful medication errors. They should NEVER be used items with a double asterisk (**). However, we hope that you will when communicating medical information. This includes internal consider others beyond the minimum TJC requirements. By using communications, telephone/verbal prescriptions, computer-generated and promoting safe practices and by educating one another about labels, labels for drug storage bins, medication administration records, hazards, we can better protect our patients. as well as pharmacy and prescriber computer order entry screens. Correction AD, AS, AU Abbreviations µg Microgram Right ear, left ear, each ear Misinterpretation Use mcg Use right ear, left ear, or each ear Mistaken ISMP 2007 Mistaken as AD, AS, AU (right ear, left ear, each ear) Mistaken as BID (twice daily) Mistaken as u (units) Use ml Premature discontinuation of medications if D/C (intended to mean Use discharge and discontinue discharge ) has been misinterpreted as discontinued when followed by a list of discharge medications Mistaken as IV or intrajugular Use injection IV Use intranasal or NAS Use half-strength or bedtime Use right eye, left eye, or each eye BT Cubic discontinue OD, OS, OU Bedtime centimeters Use bedtime cc Discharge D/C IN IJ Mistaken as IM or Use units Intranasal Half-strength At bedtime, hours of sleep Mistaken as half-strength International unit Mistaken as IV (intravenous) or 10 (ten) Once daily Mistaken as right eye (OD-oculus dexter), leading to oral liquid medications administered in the eye Orange juice Mistaken as OD or OS (right or left eye); drugs meant to be diluted in Use "orange juice" orange juice may be given in the eye os By mouth, orally The os can be mistaken as left eye (OS-oculus sinister) Use PO, by mouth, or orally or QD** Every day Mistaken as q.i.d., especially if the period after the q or the tail of Use daily the q is misunderstood as an i qhs Nightly at bedtime Mistaken as qhr or every hour Use nightly qn Nightly or at bedtime Mistaken as qh (every hour) Use nightly or at bedtime q.o.d. or QOD** Every other day Mistaken as q.d. (daily) or q.i.d. (four times daily) if the o is Use every other day poorly written q1d Daily Mistaken as q.i.d. (four times daily) Use daily etc. Every evening at 6 PM Mistaken as every 6 hours Use 6 PM nightly or 6 PM daily Subcutaneous SC mistaken as SL (sublingual); SQ mistaken as 5 every; the q in sub q has been mistaken as every (e.g., a heparin dose ordered Use subcut or subcutaneously sub q 2 hours before surgery misunderstood as every 2 hours before Spell out sliding scale; use one-half ½ Spell out sliding scale (insulin) Injection Mistaken as bedtime Use daily o.d. or OD IU** OJ HS hs Per surgery) Sliding scale (insulin) or ½ Mistaken as 55 (apothecary) Sliding scale regular insulin Mistaken as selective-serotonin reuptake inhibitor Sliding scale insulin Mistaken as Strong Solution of Iodine (Lugol's) One daily Mistaken as tid Use 1 daily 3 times a week Mistaken as 3 times a day or twice in a week Use 3 times weekly Mistaken as the number 0 or 4, causing a 10-fold overdose or greater Use unit (e.g., 4U seen as 40 or 4u seen as 44 ); mistaken as cc so dose given in volume instead of units (e.g., 4u seen as 4cc) Misinterpretation Correction q6pm, ss TIW or tiw Unit U or u** Intended SSRI SSI Designations Dose and Other Information Trailing zero after decimal point (e.g., 1.0 mg)** Naked decimal point (e.g.,.5 mg)** 1 mg Mistaken as 10 mg if the decimal point is not seen Do not use trailing zeros for doses expressed in whole numbers 0.5 mg Mistaken as 5 mg if the decimal point is not seen Use zero before a decimal point when the dose is less than a whole unit 0 any

5 graph directed graph (digraph) multi graph multi di graph pseudo graph pseudo multidigraph (!) Web sites Graph diagrams FSM diagrams 3 vertices, ABC 5 arcs Directed graph Digraph Multi-digraph Has an initial state Here B FSA has a terminal state

6 Chromatic number is 3 Chromatic number = 4 You can tell when you move around!!log 2 (chromatic number)" =! minimum number of on/off indicators Chromatic number = 4!log 2 (4)" = 2 2 indicators Used correctly

7 What s wrong? Interactive systems are directed Same chromatic number but Representing graphs Pointers, lists, Matrices Adjacency matrix Transition matrix Web: XML, SCXML, HTML Implicitly Representing digraphs Ordered pairs! {{1, 2}, {1, 4}, {2, 1}, {2, 3}, {3, 1}, {2, 4}, {2, 4}, {3, 4} } Adjacency lists! {{2, 4}, {1, 3, 4, 4}, {1, 4}, {} }

8 Representing digraphs Representing digraphs JSON! [[1, 2], [1, 4], [2, 1], [2, 3], [3, 1], [2, 4], [2, 4], [3, 4] ] Adjacency matrix! Representing digraphs { "notes": "demo", "modeltype": "colors", "buttons": ["A","B","C","D"], "statenames": ["1","2","3", "4"], "fsm": [[1,3,0,0],[0,1,2,3],[0,3,2,2], [3,3,3,3]], "startstate": 1, "state": 1, "manual": ["red","green","blue","yellow"], "action": ["press","pressed","pressing"], "errors": "never", "graphics": "colors.jpg" } Counting choices in one step the adjacency matrix M!

9 Counting choices Counting choices in two steps the matrix M.M in three steps the matrix M 3!! Counting choices Representing graphs in 1, 2 or 3 steps the matrix M+M 2 +M 3 Shortest paths!!

10 Usability The more ways the easier and more forgiving The longer the shortest path the harder to use Useful properties Distance d(a, b) Shortest distance from a to b Average cost of all paths Worst-cost path Eccentricity Radius (centre) Diameter (periphery) Hinge Bridge Cycle Randomly Eulerian More terms Connected, directed graphs Tree - connected, no cycles, exactly one path between any pair of vertices Directed, acyclic graph - DAG) General graph - has cycles

11 Special graphs Null graph Bipartite graph Complete graph Tree Planar graph Cycle (i.e., graph that is only a cycle) Simple questions Eulerian? Connected? Components of a graph are connected Strongly connected? Hamiltonian? Chromatic number? More questions Deep questions Traveling salesman Chinese postman What is the user model? It s obviously equivalent to a graph How are graphs related? Is the user model a subgraph? What is usability in graph theory terms?

12 Two more topics Summary Scale free networks Come to lecture on Friday in SURF room A city is not a tree Christopher Alexander, Design, No 206, February 1966, pp Read Chapter 8 Devices User manuals User models all the same thing Read A city is not a tree Sets Maths of graphs Just a collection of (different) things Things in sets are usually related a set of people a set of menu commands a set of numbers a set of sets eg, a university is a set of departments,

13 Graph layout Relation A relation R is a set Unsolved Algorithms Perceptual psychology a R b <a,b> R E.g., equals = {{0,{0}},{1,{1}},{2,{2}} } Except Arcs may be undirected Like a symmetric relation Arcs may be in parallel No relation equivalence Arcs and vertices may be named or labeled Labeled graphs Vertices are always labeled Edges may be labeled with names Edges may be weighted with numbers Typically, introduce functions: e.g., Labels: edge string

14 Graph terminology A set of VERTICES (plural of VERTEX) A set of ARCS (or DIRECTED EDGES) Each ARC is a pair of VERTICES If the order matters, it s an ARC And can be drawn as an arrow If the order does not matter, it s an EDGE What s the problem? Interactive systems are typically too big and unwieldy to think about How can you pick out interesting stuff? Graphs are a vocabulary for talking about interaction design More to devices Displays, indicators Modes Maths Actions: Action x States States Indicators: States P Indicators Programming function action(a, state) { ; return state; } function indicators(state) { ; return inds; }