24-29 April1993
`
`IN1*RCHI’9
`
`The Limits Of Expert Performance Using Hierarchic
`Marking Menus
`
`Gordon Kurtenbach
`
`and William
`
`Buxton
`
`Phone:
`
`(416) 978-6619,
`
`Science
`Dept. of Computer
`University
`of Toronto
`Toronto, Ontario Canada, M5S lA1
`Email:
`gordo@dgp.toronto.
`edu, willy@dgp.toronto.edu
`
`ABSTRACT
`A marking menu allows a user to perform a menu selection
`by either popping-up a radial (or pie) menu, or by making a
`straight mark in the direction of
`the desired menu item
`without popping-up the menu. A hierarchic marking menu
`uses hierarchic radial menus and “zig-zag” marks to select
`from the hierarchy. This paper experimentally investigates
`the bounds on how many items can be in each level, and
`how deep the hierarchy can be, before using a marking to
`select an item becomes too slow or prone to errors.
`
`KEYWORDS: Marking menus, pie menus, gestures, pen
`based input, accelerators, input devices
`
`INTRODUCTION
`I got a
`into the restaurant
`times I went
`The first
`couple of
`ordered
`menu
`and surveyed my
`choices.
`I generally
`vermicelli
`and barbecue pork by saying “dish number 30,
`please”. On myjifth
`or sixth visit
`I knew what
`I wanted and
`was in a hurry.
`I didn’
`t wait
`to see a menu.
`I
`looked my
`waiter
`in the eye and said,
`“Lloyd,
`bring me a number 30”.
`Things happen faster when you know what you want.
`
`behind an interaction
`This story reveals the philosophy
`technique we call “marking menus”. Marking menus are a
`type of pop-up menu where,
`if
`the user can recall
`the
`location of the item in the menu,
`the item can be selected
`without having to pop-up the menu. Just lie
`in the story,
`it’s nice not having to wait
`for Lloyd to bring a menu when
`you know what you want and how to order it.
`
`interfaces.
`Menus are used extensively in human computer
`They provide critical
`information on what commands are
`available and a way to invoke commands. Unfortunately,
`many computer menus do not provide the kind of service
`that the restaurant
`in our example does. One cannot order
`without having to look at
`the menu and this can be a
`problem. Some menus require substantial computing before
`display and this delays the user. Also, menus appearing and
`disappearing
`on the screen can be visually
`disruptive.
`Finally, a menu may obscure objects on the screen that are
`the focus of attention.
`
`of
`
`copv
`
`is
`this material
`all or part
`fee
`without
`to
`Permission
`for
`or dwtributed
`are not made
`the copies
`that
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`granted
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`and the
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`direct
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`and its date
`appear,
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`IS given
`of
`title
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`IS by permission
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`Machinery.
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`or
`to repubhsh,
`requ!res
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`andlor
`spec!flc
`permission.
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`e 1993
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`-575 -5/93 /0004
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`/04 S2...
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`$1 .50
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`482
`
`Some systems do provide methods to by-pass menus but the
`by-pass mechanism requires an action that
`is radically
`different
`than selecting using the menu. For example,
`in
`some systems, a user selects from a menu using the mouse
`but by-passes the menu using an “accelerator key” on the
`keyboard. Using our restaurant example again, tlis would
`be like changing from ordering verbally, when one has the
`menu, to ordering with hand signals when one doesn’t have
`the menu. The problem is that one has to learn two different
`protocols.
`
`Marking menus are designed to overcome this problem.
`Using a marking menu with a pen based computer works as
`follows. A novice user prasses down on the screen with the
`pen and waits for a short interval of time (approximately 1/3
`second). A radial menu [13]
`[4] then appears directly under
`the tip of the pen. A user then highlights an item by keeping
`the pen pressed and making a stroke towards the desired
`item.
`If
`the item has no sub-menu, the item can be selected
`by lifting the pen.
`If
`the item does have a sub-menu,
`it is
`displayed.
`The user then continues, selecting from the
`newly displayed sub-menu. Figure 1 (a) shows an example.
`Lifting the pen will cause the current series of highlighted
`items to be selected. The menus are then removed from the
`screen. At any time a user can indicate “no selection” by
`moving the pen back to the center of the menu before lifting,
`or change the selection by moving the pen to highlight
`another item before lifting. Finally a user can “back-up”
`to
`a previous menu by pointing to its center.
`
`The other, faster, way to make a selection without popping
`up the menu is by &awing a mark. A mark can be drawn by
`pressing the pen down and immediately moving. The shape
`of the mark dictates the particular series of items selected
`from the menu hierarchy. Figure 1 (b) shows an example.
`
`to note is that
`point
`important
`The first
`physical
`the
`in selecting
`an item from the menu is
`involved
`movement
`to the physical movement
`required
`to make the
`identical
`item. With marking menus, a
`mark corresponding
`to that
`the physical movement
`involved in
`user actually rehearses
`making the mark every time a selection from the menu is
`made. We believe that this helps users learn the markings.
`The second point
`to note is that supporting
`radial menus
`with markings
`in this way helps users make an efficient
`from novice to expert. Novices perform menu
`transition
`selection because they are not familiar with the menu and its
`layout.
`As they become experts,
`they begin to use the
`
`GOOGLE EX. 1019
`
`Google v. Philips
`
`

`
`INTIRCHI’93
`
`24-29 April1993
`
`Is!!ud
`
`(a)
`
`1
`
`J
`
`(b)
`
`Figure 1. Hierarchic marking menus can be selected from using two different methods. Using method (a), radial menus can
`be sequentially
`displayed and selections mude. Method (b) uses a murking to muke the same selection. Method (a) is good
`when the user is unfamiliar
`with the menu. Method (b) is good when the user is familiar
`with the menu and wants to avoid
`waiting for
`the display of each menu.
`
`“learn on the job”
`in effect,
`markings instead. Novices,
`because these two activities are so similar.
`
`Is marking much faster than using the menu? In a study of
`user behavior with non-hierarchic marking menus in a real
`application, we found that using a mark was approximately
`3.5 times faster
`than using the menu, even if
`the 1/3 of
`second delay to pop-up the menu was subtracted from menu
`selection time (for example, one user required on average
`0.2 seconds to select using a mark and 0.7 seconds to select
`using the menu) [8]. Displaying the menu actually takes a
`small amount of
`time (O.15 seconds in our system). The
`larger amount of time is consumed waiting for the user to
`react to the display of the menu, even if
`the location of the
`desired menu item is known. While these time savings may
`seem trivial,
`one user performed approximately
`15,000
`selections over 36 hours of work. Using marks helped her
`complete the task 1.25 hours sooner.
`
`to address questions one asks
`We performed an experiment
`when designing an interface that will use hierarchic marking
`menus.
`
`Ql: Are hierarchic marking menus a feasible idea? Non-
`hierarchic marking menus have proven to be feasible [9].
`Other research has shown that radial menus are faster than
`linear menus [1]. Thus we can expect marking menus, even
`without using the faster marking ahead technique,
`to be
`faster
`that
`traditional
`linear menus. Nevertheless,
`the
`question remains as to whether
`it
`is possible to use a
`marking to select hierarchic menu items.
`
`Just how
`Q2: How deep can one go using a marking?
`“expert” could users become? Could an experienced user
`
`from a menu which had 3 levels of
`use a mark to select
`hierarchy and twelve items at eaeh level? By discovering
`the limitations of the technique we would be able to predict
`what menu configurations, with enough practice, will
`lead to
`reliable
`selection
`using a marking,
`and which menu
`configurations,
`regardless of
`the amount of practice, will
`never permit reliable selection using a marking. Also, will
`some items be easier to select regardless of depth? For
`example,
`it seems easier to select items that are on the up,
`down, left and right axes even if the menus are cluttered and
`deep.
`
`Is breadth better than depth? Will wide and shallow
`Q3:
`menu structures be easier to access with markings than thin
`and deep ones?
`Traditional
`menu
`designs
`have
`breadth/depth trade-offs [5]. What sort of trade off exists
`for marking menus?
`
`Q4:
`in poorer
`result
`Will mixing menu breadths
`performance?
`A previous experiment on non-hierarchic
`marking menus has shown that
`the number of
`items in a
`menu and the layout of
`those items in the menu affects
`selection
`performance
`when markings
`are used [9].
`Specifically, menus with 2,4,6,
`8 and 12 items work quite
`well
`for markings. What will be the effect of selecting from
`menu configurations where the number of items in a menu
`varies from sub-menu to sub-menu?
`
`the pen be more suitable than the mouse for
`Q5: Will
`making marks? The experiment
`mentioned
`above also
`compared making selections from non-hierarchic marking
`menus using a tablet with a stylus, a trackball and a mouse.
`The traekball was the worst performer, while the tablet with
`stylus and mouse performed equally. However, hierarchic
`
`483
`
`GOOGLE EX. 1019
`
`Google v. Philips
`
`

`
`24-29 April1993
`
`lNlIRcHr93
`
`marking menus require more complex marks. Will
`mouse prove inadequate?
`
`the
`
`THE EXPERIMENT
`
`Basic Design
`
`In order to determine the limits of performance, we needed
`to simulate expert behavior. We defined expert behavior as
`the situation where the user is completely familiar with the
`contents and layout of
`the menu and can easily recall
`the
`marking needed to select a menu item. To make subjects
`“completely familiar” with the menu layouts we chose menu
`items whose layout could be easily memorized. We tested
`menus with 4, 8 and 12 items. For a menu of 4 items, the
`labels were laid out like the four points of a compass: “N”,
`“E”,
`“S” and “W’. We referred to this type of menu as a
`compass4. Similarly
`a “compass8” menu had these four
`directions plus “NE”,
`“SE”,
`“SW and “NW”. Menus with
`twelve items, referred to as a “clock” menus, were labeled
`like the hours on a clock.
`
`users of real applications ever be as familiar with
`Will
`menus as they are with a clock or compass? We believe the
`answer is yes and base this on three pieces of evidence.
`First, our own behavioral study of users using a marking
`menu in a real application shows, with practice, markings
`are used over ninety percent of
`the time [8].
`Other
`researchers have reported this type of
`familiarity with pie
`menus [4]. Second, research has shown that the effects of
`menu organization disappear with practice [2] [10].
`In other
`words, with practice, users memorize menu layouts and
`navigate directly to the desired menu item. Finally,
`it must
`be remembered that a user does not have to memorize the
`layout of an entire menu. For example, a hierarchic marking
`
`the user might only
`menu could contain 64 items but
`memorize the markings needed to select
`the two most
`frequently used menu items.
`
`in our experiment was as
`The general design of a trial
`follows.
`The system would ask the subject
`to select a
`certain item using a marking (the menu could not be popped
`up by the subject). The subject would draw the marking and
`the system would then record the time taken, and whether or
`not a successful selection was made. We would then vary
`the menu contlguration and input device and see what effect
`these variables had on selection performance.
`
`Method
`
`Subjects: Twelve right handed subjects were recruited from
`University of Toronto. All subjects were skilled in using a
`mouse but had little or no experience using a pen on a pen
`based computer.
`
`Equipment: A Momenta pen based computer was used. The
`input devices consisted of a Microsoft mouse for
`IBM
`personal computers, and a Momenta pen and digitizer.
`
`The type of menu
`A trial occurred as follows.
`Task:
`configuration currently being tested would appear in the top
`left comer of the screen. A small circle would appear in the
`center of the screen. A subject would then press and hold
`the pen or mouse button over the circle. The system would
`then display instructions describing the target at the top
`center of
`the screen. A subject would then respond by
`drawing a mark that was hoped to be the correct response.
`The system would respond by displaying
`the selection
`produced by the marking.
`If the selection did not match the
`target,
`the system would beep to indicate an error. The
`
`Menu is compaas8:compass8
`
`Select NE - S
`Response NE - S
`
`N
`I
`
`NE
`
`NW
`““”
`
`w
`
`NW
`
`w
`
`Sw
`
`N
`
`s
`
`the end of a trial where the target was “NE-S”.
`screen at
`2: The experiment
`Figure
`the marking was completed,
`After
`system displayed ~he menus along the murking to indicate to the subject
`the accuracy of their marking.
`
`the
`
`484
`
`GOOGLE EX. 1019
`
`Google v. Philips
`
`

`
`24-29 April1993
`
`0 mouse
`fl
`pen
`
`Jy
`
`1
`
`40
`
`35-
`
`30-
`
`25-
`
`20-
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`
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`
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`
`INERCHI’93
`
`4.5
`
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`
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`
`I
`
`,
`
`4,1
`
`1
`4,2
`
`,
`4,3
`
`(a)
`
`m
`1
`1
`1
`4,4
`8,1
`8,2
`8,3
`Breadth, Depth
`
`1
`8,4
`
`1
`1
`1
`1
`12,1 12,2 12,3 12,4
`
`;’
`
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`
`,,,
`
`,,,
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`
`4,1
`
`4,2
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`4,3
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`8,2
`8,1
`4,4
`Breadth, Depth
`
`(b)
`
`8,4
`
`12,1 12,2 12,3 12,4
`
`Figure 3: Response time and percentage of errors as a function
`average of 288 trials.
`
`of menu breadth, depth and input device. Each data point
`
`is the
`
`system would then display each menu in the current menu
`configuration at its appropriate location along the marking
`and indicate the selection from each menu. A subject’s
`left of the screen.
`score would then be shown in the lower
`Figure 2 shows the experimental screen at this point.
`If a
`selection was incorrect, a subject would lose 100 points and
`the trial would be recorded as an error.
`If a selection was
`correct, the subject would earn points based on how quickly
`the response was executed. Response time was defined as
`the time that elapsed between the display of the target and
`the completion of the marking.
`
`three factors, device, breadth and depth were
`Design: All
`within-subject.
`Trials were blocked by input device with
`every subject using both the pen and the mouse. One half of
`the subjects began with the pen frost while the other half
`began with the mouse. For each device, a subject was tested
`on the 13 menu configurations (breadths 4, 8 and 12 crossed
`with depths 1 to 4, plus the mixed menu configuration of
`clock: compass8:clock).
`Menu
`configurations
`were
`presented in random order. For each menu configuration, a
`subject performed 24 trials. During the 24 trials, subjects
`were repeatedly asked to select 1 of 3 different
`targets.
`Each target appeared eight
`times in the 24 trials but
`the
`order of appearance was random.
`
`trials for a particular menu
`Before starting a block of
`configuration, subjects were allowed 8 seconds to study the
`menu configuration. Before starting trials with a particular
`input device, a subject was given ten practice trials using the
`device on a compass4:compass4:compass4 menu.
`
`Results and Discussion
`
`input device, breadth and depth affected
`three. factors,
`All
`response time. Analysis of variance revested a three way
`interaction
`between input device,
`breadth and depth
`(F(6,66)=3.32, p < .05) affecting response time. Figure 3 (a)
`shows these relationships. As one would expect, increasing
`breadth and depth increases response time, however,
`
`degraded more quickly with the
`subjects’ performance
`mouse than with the pen.
`
`faster with the pen than
`Subjects responded significantly
`1)=19.7, p c .001). The response time
`with the mouse (F(l,l
`averaged across all subjects, breadths and depths for the pen
`was 1.69 seconds while the mouse averaged 2.07 seconds.
`As menu breadth and depth increased subjects’ performance
`with the two devices began to differ. This is shown in figure
`3.
`
`Subjects produced significantly more errors with the mouse
`than with the pen (F(l,l 1)=6.41, p < .05). Both depth and
`breadth interacted to affect error rate (F(6,66)=12.28, p <
`.00 1).
`Figure 3 (b) shows that mouse and pen error
`percentages began to differ once menu breadth reached eight
`items. For either device, error rates were below 10% for up
`to menus of breadth 8 and depth 2.
`
`We tested for effects of mixing menu breadths in menu
`configurations
`by
`comparing
`the performance
`of a
`cloclcclock:clock menu with a clockcompass&clock menu.
`We found no significant performance differences between
`the two menu configurations.
`
`In order to test the hypothesis that markings which consist
`of “on axis” items (items on the vertical and horizontal axes)
`out-perform “off axis” markings, we picked targets for
`menus of breadth twelve, depths two,
`three and four such
`that the experimental data could be divided into 3 groups.
`With each group we associated an “off axis-level”: al, a2
`and a3. Experimental data was placed in group al
`if
`the
`target consisted strictly of menu items that were on-axis,
`such as “12-3-9-3”. Group a3 consisted of data on targets
`that consisted of entirely off-axis targets such as “l-2-l-2”.
`Group a2 consisted of data on targets that were a mixture of
`on-axis and off-axis menu items, such as “12-7-3-9.
`Figure
`4 shows that axis level had a significant effect on response
`time (F(2,22)= 104.84, p < .001) and on percentage of errors
`(F(2,22)=36.2, p < .001). Figure 4 (a) shows how the type
`of device interacted with off-axis level (F(2,22)=6.93, p <
`
`485
`
`GOOGLE EX. 1019
`
`Google v. Philips
`
`

`
`24-29 April1993
`
`lNTf!RcH1’
`
`response time on the
`.05). This indicates that subjects’
`worse off-axis targets did not degrade as badly with the pen
`as it did with the mouse.
`
`CONCLUSIONS
`We can now revisit
`paper.
`
`the questions posed at the start of this
`
`Ql: Are hierarchic marking menus a feasible idea? Even if
`using a marking to access an item is too hard to draw or
`carmot be remembered, a user can perform a selection by
`displaying
`the menus. Nevertheless,
`since the subjects
`could perform the experiment,
`it
`is feasible that markings
`could be used to select hierarchic menu items.
`
`Q2: How deep can one go using a marking? Our data
`indicates
`that
`increasing depth increases response time
`linearly.
`The limiting factor appears to be error rate. For
`menus of four items, even up to four levels deep, the error
`rate was less than ten percent. This is also true for menus of
`eight
`items, up to a depth of
`two. However, when using
`markings for menus with eight
`items or more, at depths
`greater than two, selection becomes error-prone, even for
`the expert. However, our “off-axis”
`analysis indicates that
`the source of poor performance at higher breadths and
`depths is due to selecting “off-axis”
`items. Thus, when
`designing a wide and deep menu, the frequently used items
`could be placed at “on-axis”
`locations. This would allow
`some items to be accessed quickly
`and reliably with
`markings, despite the breadth and depth of the menu.
`
`to this
`The answer
`rate?
`is an acceptable error
`What
`question depends on the consequences of an error, the cost
`of undoing an error or
`redoing the command, and the
`attitude of
`the user.
`For example, we have data that
`indicates,
`in certain situations, experts produce more errors
`than novices
`[11].
`The experts were skilled at error
`recovery and thus elected to trade accuracy for
`fast
`task
`performance. Our experiences with marking menus with six
`items being used in a real application indicates that experts
`perceived selection to be error-free. Other research reports
`that menus with up to eight
`items produce acceptable
`
`performance [4]. Marking menus present a classic time
`versus accuracy trade-off.
`If
`the marking error rate is too
`high, a user can always use the slower but more accurate
`method of popping up the menus to make a selection.
`
`Is breadth better than depth? For menu configurations
`Q3:
`that resulted in acceptable performance, breadth and depth
`seems to be an even trade-off
`in terms of response time and
`errors. For example, accessing 64 items using menus of
`four
`items,
`three deep, is approximately
`as fast as using
`menus
`of eight
`items,
`two
`deep, and both
`have
`approximately
`equivalent error
`rates. Thus, within this
`range of menu configurations,
`a designer can let
`the
`semantics of menu items dictate whether menus should be
`narrow and deep, or wide and shallow.
`
`Q4:
`in poorer
`result
`Will mixing menu breadths
`performance? The experiment did not show this to be true.
`This may be due to the fact
`that our menu labels strongly
`suggested the correct angle to draw at, and therefore
`confusion was avoided. A stronger test might be to compare
`mixing menu breadths
`using less suggestive
`labels.
`However,
`our
`results
`do indicate
`that, with
`enough
`familiarity
`with the menus, mixing
`breadths is not a
`significant problem.
`
`than the mouse for making
`the pen be better
`Q5: Will
`marks? Overall, subjects performed better with the pen than
`with the mouse. However,
`for small menu breadths and
`depths, subjects’ performance, with either the mouse or pen,
`was approximately
`equivalent. We found this extremely
`encouraging because it
`implies that a marking menu is an
`interaction technique that not only takes advantage of
`the
`pen but also remains compatible with the mouse.
`
`FUTURE DIRECTIONS
`We are currently experimenting with designing interfaces
`that use marking menus. When displays become small or
`very large, marking menus are effective.
`A mark or
`selection can be made at a user’s current
`location without a
`trip to a menu bar or tool pallet. We are currently trying to
`exploit
`this advantage on a electronic whiteboard system
`
`Off AXIS Level
`
`0 mouse
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`
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`
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`
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`
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`
`a
`
`1
`
`al
`
`a”2
`Off Axis Level
`
`a‘3
`
`(a)
`
`Figure 4: Average response time and percentage
`
`of errors for
`
`targets with an increasing
`
`number of “off-axis”
`
`items.
`
`486
`
`GOOGLE EX. 1019
`
`Google v. Philips
`
`

`
`lNTfRcH1’93
`
`24-29 April1993
`
`[3]. We are also using marking menus on small hand-held
`computers [12]. On small screens, since both the menu and
`mark “go-away” once performed, no vrduable screen space
`is consumed.
`
`to gather both programmer and user
`We are continuing
`feedback on using markings menus in many applications
`[6],
`
`A marking menu is a specific instance of an interaction
`technique that supports both the novice and expert user, and
`trains a novice to become expert. We are investigating how
`this philosophy can be applied to other types of interaction
`techniques and markings.
`
`ACKNOWLEDGMENTS
`We thank the members of the Input Research Group at the
`University
`of Toronto who provided the forum for
`the
`design and execution
`of
`this project. This work was
`performed in the Dynamic Graphics Project laboratory at the
`University
`of Toronto,
`to whom we are grateful. We
`especially
`thank Scott Mackenzie
`for his advice on
`statistical matters and Beverly Harrison for her comments
`on experimental design. We gratefully
`acknowledge the
`financial support of the Natural Sciences and Engineering
`Research Council
`of Canada, Digital
`Equipment
`Corporation, Xerox PARC and Apple Computer.
`
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