Trigger-Action Programming (TAP) has been shown to support end-users' rule-based mental models of context-aware applications. However, when desired behaviours increase in complexity, this can lead to ambiguity that confuses events, states, and how they can be combined in meaningful ways. Blocks programming could provide a solution, through constrained editing of visual triggers, conditions and actions. We observed slips and mistakes by users performing TAP with Jeeves, our domain-specific blocks environment, and propose solutions.Postprin

Quigley, Aaron

Rough, Daniel

English

Trigger-Action Programming (TAP) has been shown to support end-users' rule-based mental models of context-aware applications. However, when desired behaviours increase in complexity, this can lead to ambiguity that confuses events, states, and how they can be combined in meaningful ways. Blocks programming could provide a solution, through constrained editing of visual triggers, conditions and actions. We observed slips and mistakes by users performing TAP with Jeeves, our domain-specific blocks environment, and propose solutions.</p

University of Dundee Online Publications

                                                                    University of DundeeTAPping into mental models with blocksRough, Daniel; Quigley, AaronPublished in:Proceedings - 2017 IEEE Blocks and Beyond Workshop (B&B)DOI:10.1109/BLOCKS.2017.8120429Publication date:2017Document VersionPeer reviewed versionLink to publication in Discovery Research PortalCitation for published version (APA):Rough, D., & Quigley, A. (2017). TAPping into mental models with blocks. In F. Turbak, C. Kelleher, J. Gray, &M. Sherman (Eds.), Proceedings - 2017 IEEE Blocks and Beyond Workshop (B&B) (pp. 115-116). IEEE.https://doi.org/10.1109/BLOCKS.2017.8120429General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 19. Apr. 2023TAPping into Mental Models with BlocksDaniel RoughSchool of Computer Science, University of St Andrewsdjr53@st-andrews.ac.ukAaron QuigleySchool of Computer Science, University of St Andrewsaquigley@st-andrews.ac.ukAbstract—Trigger-Action Programming (TAP) has been shownto support end-users’ rule-based mental models of context-aware applications. However, when desired behaviours increasein complexity, this can lead to ambiguity that confuses events,states, and how they can be combined in meaningful ways. Blocksprogramming could provide a solution, through constrainedediting of visual triggers, conditions and actions. We observedslips and mistakes by users performing TAP with Jeeves, ourdomain-specific blocks environment, and propose solutions.I. INTRODUCTIONWith the increasing ubiquity of smartphones, wearabledevices, and home automation systems in our everyday lives,a need has arisen to support end-users in customising thebehaviour of their technology. Today, a range of commercialplatforms aim to put the power of context-aware computinginto the hands of non-programmers. A prevalent example isIFTTT (https://ifttt.com/), an app that allows users to cus-tomise their smartphones and external devices. Its growinguser base demonstrates a strong desire for such functionality.Automation apps have succeeded in lowering the barriersto simple trigger-action programming (TAP) by end-users.For example, IFTTT allows a user to pick an event, andan associated action, from a list of options. However, suchsimplicity necessitates a sacrifice in flexibility, and multipleactions or triggers cannot be combined. Although this flexi-bility is desired by users, previous work shows that they designtrigger combinations with ambiguous interpretations [1], [2].One solution to this problem is to actively disallow theseambiguous trigger combinations [2]. The syntax-directed edit-ing of blocks supports this strategy. However, even if blockssupport clearly defined triggers, can end-users make senseof correct combinations? Further, do blocks raise issues thattext avoids? We conducted a usability study of Jeeves, ourblocks environment [3] for creating experience sampling apps,recruiting 10 participants with limited or no programming ex-perience. We briefly discuss pertinent issues they encounteredin TAP, and suggest potential solutions.II. VISUAL TAP CONCEPTSPrevious work has shown that natural language is unsuitablefor making the distinction between triggers (discrete events)and conditions (ongoing states) [4]. Even in a jigsaw-puzzlebased composition environment, triggers and actions can beconfused if they are not distinct [5]. Inspired by the Blocklyeditor [6] and similar environments, Jeeves blocks are sep-arated into ‘palettes’. An example of this distinction can beFig. 1. A Location trigger, with an if-block containing a location condition,and an action to capture the current locationseen in Figure 1. The trigger represents an event — a user’slocation, acquired through their smartphone’s GPS sensor, haschanged to Home. The if-block then evaluates its condition,representing whether a user is currently Home. Finally, theaction captures and stores data from the GPS sensor. Whilesuch an execution is nonsensical, it serves to illustrate thedifferent uses of smartphone sensor functionality in Jeeves.Unambiguous context-aware behaviours should be com-posed of one discrete event trigger, with an optional numberof state conditions [1], [2]. As shown in Figure 1, Jeeves,like other blocks languages, supports these constraints throughthe visual affordance of correct connections. With no external‘notches’, event triggers cannot be nested together. Multipleconditions can be nested, but only within an event trigger.III. SLIPS AND MISTAKESWe observed that Jeeves blocks supported our participantsin thinking about triggers, conditions and attributes correctlyin task completion. However, errors from both mistakes andslips resulted in obscurity and damage of mental models [7].A. From Slips To FallsIn part of a task, participants had to set a ‘Do Not Disturb’attribute to be true. Figure 2 (Right) shows that a ‘near miss’had a negative impact on their mental model of how blockscould be combined. One participant who made this slip, whenlater asked about her understanding of the ‘set attribute’ action,stated that she “couldn’t work out how to use it”, despitepreviously demonstrating a correct assumption of the action’sbehaviour. Participants learn that a block snapping into placeindicates correctness, so when this fails to happen, correctchoices are discounted and mental models break down.© AAM, 2019. This is the author’s version of the work.  It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in C&T 2019: The 9th International Conference on Communities & Technologies - Transforming Communities [https://doi.org/10.1145/3328320.3328371].Fig. 2. Left: A correct snap supports a user’s mental model. Right: A ‘near miss’ damages the mental modelFig. 3. Language ambiguity caused trigger, action and condition confusionB. Blame The NameOrganising blocks by type into palettes supports recognitionover recall. However, our participants’ inexperience with TAPcaused issues with recognition, thus they would hunt for ablock by name, regardless of its type. In one task, we askedparticipants to turn on the Bluetooth sensor when a user returnshome. Figure 3 shows two examples of participants failing tofind the appropriate ‘capture data’ action — they instead triedadjusting the sensor trigger (top), or used a sensor conditionin place of the action (bottom). When they found and used thecorrect action, they expressed doubt as to correctness.IV. REBUILDING BLOCKSHow do we rebuild a damaged mental model? Based onfeedback and observations of our study participants, we pro-pose two potential solutions, which will be incorporated intoJeeves and evaluated in a further study.Baudisch et al. [8] demonstrate their ‘drag-and-pop’ inter-action, supporting drag-and-drop on large displays, wherebyan icon’s compatible drop locations are drawn towards it. Weare currently considering a similar solution we call ‘lock-onblocks’, which will visually suggest compatible locations fordragged blocks, resolving certain mistakes, as well as reducingslips. As suggested by one participant, simple highlighting ofcorrect locations for a dragged block may also be sufficient.The question “Does that block live there?” was raised byone of our participants, and echoed in various forms by others.Forgetting where to find correct blocks, many would search inthe ‘conditions’ palette for an action. Conversely, they wouldsometimes look to actions for functionality provided by acondition. Rodriguez et al. demonstrated that block categorynames can have a significant effect on perceived usability [9].As a flexible solution, we propose that having the user click ona particular drop location would automatically switch them tothe relevant palette, guiding their search. This could reinforcehow triggers, actions and conditions combine.V. CONCLUSIONWe propose that blocks can support TAP, but care must betaken to reinforce fragile assumptions when they are correct.REFERENCES[1] B. Ur, E. McManus, M. Pak Yong Ho, and M. L. Littman, “Practicaltrigger-action programming in the smart home,” in Proc. 32nd Annu.ACM Conf. Human factors in computing systems, 2014, pp. 803–812.[2] J. Huang and M. Cakmak, “Supporting mental model accuracy in trigger-action programming,” in Proc. 2015 ACM Int. Joint Conf. Pervasive andUbiquitous Computing, 2015, pp. 215–225.[3] D. Rough and A. Quigley, “Jeeves - A Visual Programming Environmentfor Mobile Experience Sampling,” Visual Languages and Human-CentricComputing (VL/HCC), 2015 IEEE Symp., pp. 121–129, 2015.[4] M. Garcı́a-Herranz, P. Haya, and X. Alamán, “Towards a UbiquitousEndUser Programming System for Smart Spaces,” Journal of UniversalComputer Science, vol. 16, no. 12, pp. 1633–1649, 2010.[5] Y. Dahl and R. M. Svendsen, “End-user composition interfaces for smartenvironments: A preliminary study of usability factors,” in Lecture Notesin Computer Science, vol. 6770 LNCS, no. 2, 2011, pp. 118–127.[6] N. Fraser, “Ten things we’ve learned from Blockly,” in 2015 IEEE Blocksand Beyond Workshop (Blocks and Beyond), Oct 2015, pp. 49–50.[7] D. A. Norman, “Design rules based on analyses of human error,”Commun. ACM, vol. 26, no. 4, pp. 254–258, Apr. 1983.[8] P. Baudisch, E. Cutrell, D. Robbins, M. Czerwinski, P. Tandler, B. Bed-erson, A. Zierlinger, and M. Push, “Drag-and-Pop and Drag-and-Pick:Techniques for accessing remote screen content on touch- and pen-operated systems,” Proc. INTERACT ’03, pp. 64–57, 2003.[9] F. J. Rodrı́guez, K. M. Price, J. Isaac, K. E. Boyer, and C. Gardner-Mccune, “How Block Categories Affect Learner Satisfaction with aBlock-Based Programming Interface.”

TAPping into mental models with blocks

Rough, D.

Quigley, A.

St Andrews Research Repository

TAPping into Mental Models with BlocksDaniel RoughSchool of Computer Science, University of St Andrewsdjr53@st-andrews.ac.ukAaron QuigleySchool of Computer Science, University of St Andrewsaquigley@st-andrews.ac.ukAbstract—Trigger-Action Programming (TAP) has been shownto support end-users’ rule-based mental models of context-aware applications. However, when desired behaviours increasein complexity, this can lead to ambiguity that confuses events,states, and how they can be combined in meaningful ways. Blocksprogramming could provide a solution, through constrainedediting of visual triggers, conditions and actions. We observedslips and mistakes by users performing TAP with Jeeves, ourdomain-specific blocks environment, and propose solutions.I. INTRODUCTIONWith the increasing ubiquity of smartphones, wearabledevices, and home automation systems in our everyday lives,a need has arisen to support end-users in customising thebehaviour of their technology. Today, a range of commercialplatforms aim to put the power of context-aware computinginto the hands of non-programmers. A prevalent example isIFTTT (https://ifttt.com/), an app that allows users to cus-tomise their smartphones and external devices. Its growinguser base demonstrates a strong desire for such functionality.Automation apps have succeeded in lowering the barriersto simple trigger-action programming (TAP) by end-users.For example, IFTTT allows a user to pick an event, andan associated action, from a list of options. However, suchsimplicity necessitates a sacrifice in flexibility, and multipleactions or triggers cannot be combined. Although this flexi-bility is desired by users, previous work shows that they designtrigger combinations with ambiguous interpretations [1], [2].One solution to this problem is to actively disallow theseambiguous trigger combinations [2]. The syntax-directed edit-ing of blocks supports this strategy. However, even if blockssupport clearly defined triggers, can end-users make senseof correct combinations? Further, do blocks raise issues thattext avoids? We conducted a usability study of Jeeves, ourblocks environment [3] for creating experience sampling apps,recruiting 10 participants with limited or no programming ex-perience. We briefly discuss pertinent issues they encounteredin TAP, and suggest potential solutions.II. VISUAL TAP CONCEPTSPrevious work has shown that natural language is unsuitablefor making the distinction between triggers (discrete events)and conditions (ongoing states) [4]. Even in a jigsaw-puzzlebased composition environment, triggers and actions can beconfused if they are not distinct [5]. Inspired by the Blocklyeditor [6] and similar environments, Jeeves blocks are sep-arated into ‘palettes’. An example of this distinction can beFig. 1. A Location trigger, with an if-block containing a location condition,and an action to capture the current locationseen in Figure 1. The trigger represents an event — a user’slocation, acquired through their smartphone’s GPS sensor, haschanged to Home. The if-block then evaluates its condition,representing whether a user is currently Home. Finally, theaction captures and stores data from the GPS sensor. Whilesuch an execution is nonsensical, it serves to illustrate thedifferent uses of smartphone sensor functionality in Jeeves.Unambiguous context-aware behaviours should be com-posed of one discrete event trigger, with an optional numberof state conditions [1], [2]. As shown in Figure 1, Jeeves,like other blocks languages, supports these constraints throughthe visual affordance of correct connections. With no external‘notches’, event triggers cannot be nested together. Multipleconditions can be nested, but only within an event trigger.III. SLIPS AND MISTAKESWe observed that Jeeves blocks supported our participantsin thinking about triggers, conditions and attributes correctlyin task completion. However, errors from both mistakes andslips resulted in obscurity and damage of mental models [7].A. From Slips To FallsIn part of a task, participants had to set a ‘Do Not Disturb’attribute to be true. Figure 2 (Right) shows that a ‘near miss’had a negative impact on their mental model of how blockscould be combined. One participant who made this slip, whenlater asked about her understanding of the ‘set attribute’ action,stated that she “couldn’t work out how to use it”, despitepreviously demonstrating a correct assumption of the action’sbehaviour. Participants learn that a block snapping into placeindicates correctness, so when this fails to happen, correctchoices are discounted and mental models break down.Fig. 2. Left: A correct snap supports a user’s mental model. Right: A ‘near miss’ damages the mental modelFig. 3. Language ambiguity caused trigger, action and condition confusionB. Blame The NameOrganising blocks by type into palettes supports recognitionover recall. However, our participants’ inexperience with TAPcaused issues with recognition, thus they would hunt for ablock by name, regardless of its type. In one task, we askedparticipants to turn on the Bluetooth sensor when a user returnshome. Figure 3 shows two examples of participants failing tofind the appropriate ‘capture data’ action — they instead triedadjusting the sensor trigger (top), or used a sensor conditionin place of the action (bottom). When they found and used thecorrect action, they expressed doubt as to correctness.IV. REBUILDING BLOCKSHow do we rebuild a damaged mental model? Based onfeedback and observations of our study participants, we pro-pose two potential solutions, which will be incorporated intoJeeves and evaluated in a further study.Baudisch et al. [8] demonstrate their ‘drag-and-pop’ inter-action, supporting drag-and-drop on large displays, wherebyan icon’s compatible drop locations are drawn towards it. Weare currently considering a similar solution we call ‘lock-onblocks’, which will visually suggest compatible locations fordragged blocks, resolving certain mistakes, as well as reducingslips. As suggested by one participant, simple highlighting ofcorrect locations for a dragged block may also be sufficient.The question “Does that block live there?” was raised byone of our participants, and echoed in various forms by others.Forgetting where to find correct blocks, many would search inthe ‘conditions’ palette for an action. Conversely, they wouldsometimes look to actions for functionality provided by acondition. Rodriguez et al. demonstrated that block categorynames can have a significant effect on perceived usability [9].As a flexible solution, we propose that having the user click ona particular drop location would automatically switch them tothe relevant palette, guiding their search. This could reinforcehow triggers, actions and conditions combine.V. CONCLUSIONWe propose that blocks can support TAP, but care must betaken to reinforce fragile assumptions when they are correct.REFERENCES[1] B. Ur, E. McManus, M. Pak Yong Ho, and M. L. Littman, “Practicaltrigger-action programming in the smart home,” in Proc. 32nd Annu.ACM Conf. Human factors in computing systems, 2014, pp. 803–812.[2] J. Huang and M. Cakmak, “Supporting mental model accuracy in trigger-action programming,” in Proc. 2015 ACM Int. Joint Conf. Pervasive andUbiquitous Computing, 2015, pp. 215–225.[3] D. Rough and A. Quigley, “Jeeves - A Visual Programming Environmentfor Mobile Experience Sampling,” Visual Languages and Human-CentricComputing (VL/HCC), 2015 IEEE Symp., pp. 121–129, 2015.[4] M. Garcı´a-Herranz, P. Haya, and X. Alama´n, “Towards a UbiquitousEndUser Programming System for Smart Spaces,” Journal of UniversalComputer Science, vol. 16, no. 12, pp. 1633–1649, 2010.[5] Y. Dahl and R. M. Svendsen, “End-user composition interfaces for smartenvironments: A preliminary study of usability factors,” in Lecture Notesin Computer Science, vol. 6770 LNCS, no. 2, 2011, pp. 118–127.[6] N. Fraser, “Ten things we’ve learned from Blockly,” in 2015 IEEE Blocksand Beyond Workshop (Blocks and Beyond), Oct 2015, pp. 49–50.[7] D. A. Norman, “Design rules based on analyses of human error,”Commun. ACM, vol. 26, no. 4, pp. 254–258, Apr. 1983.[8] P. Baudisch, E. Cutrell, D. Robbins, M. Czerwinski, P. Tandler, B. Bed-erson, A. Zierlinger, and M. Push, “Drag-and-Pop and Drag-and-Pick:Techniques for accessing remote screen content on touch- and pen-operated systems,” Proc. INTERACT ’03, pp. 64–57, 2003.[9] F. J. Rodrı´guez, K. M. Price, J. Isaac, K. E. Boyer, and C. Gardner-Mccune, “How Block Categories Affect Learner Satisfaction with aBlock-Based Programming Interface.”

                                                                    University of DundeeTAPping into mental models with blocksRough, Daniel; Quigley, AaronPublished in:Proceedings - 2017 IEEE Blocks and Beyond Workshop (B&amp;B)DOI:10.1109/BLOCKS.2017.8120429Publication date:2017Document VersionPeer reviewed versionLink to publication in Discovery Research PortalCitation for published version (APA):Rough, D., & Quigley, A. (2017). TAPping into mental models with blocks. In F. Turbak, C. Kelleher, J. Gray, &M. Sherman (Eds.), Proceedings - 2017 IEEE Blocks and Beyond Workshop (B&B) (pp. 115-116). IEEE.https://doi.org/10.1109/BLOCKS.2017.8120429General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 07. Jul. 2020TAPping into Mental Models with BlocksDaniel RoughSchool of Computer Science, University of St Andrewsdjr53@st-andrews.ac.ukAaron QuigleySchool of Computer Science, University of St Andrewsaquigley@st-andrews.ac.ukAbstract—Trigger-Action Programming (TAP) has been shownto support end-users’ rule-based mental models of context-aware applications. However, when desired behaviours increasein complexity, this can lead to ambiguity that confuses events,states, and how they can be combined in meaningful ways. Blocksprogramming could provide a solution, through constrainedediting of visual triggers, conditions and actions. We observedslips and mistakes by users performing TAP with Jeeves, ourdomain-specific blocks environment, and propose solutions.I. INTRODUCTIONWith the increasing ubiquity of smartphones, wearabledevices, and home automation systems in our everyday lives,a need has arisen to support end-users in customising thebehaviour of their technology. Today, a range of commercialplatforms aim to put the power of context-aware computinginto the hands of non-programmers. A prevalent example isIFTTT (https://ifttt.com/), an app that allows users to cus-tomise their smartphones and external devices. Its growinguser base demonstrates a strong desire for such functionality.Automation apps have succeeded in lowering the barriersto simple trigger-action programming (TAP) by end-users.For example, IFTTT allows a user to pick an event, andan associated action, from a list of options. However, suchsimplicity necessitates a sacrifice in flexibility, and multipleactions or triggers cannot be combined. Although this flexi-bility is desired by users, previous work shows that they designtrigger combinations with ambiguous interpretations [1], [2].One solution to this problem is to actively disallow theseambiguous trigger combinations [2]. The syntax-directed edit-ing of blocks supports this strategy. However, even if blockssupport clearly defined triggers, can end-users make senseof correct combinations? Further, do blocks raise issues thattext avoids? We conducted a usability study of Jeeves, ourblocks environment [3] for creating experience sampling apps,recruiting 10 participants with limited or no programming ex-perience. We briefly discuss pertinent issues they encounteredin TAP, and suggest potential solutions.II. VISUAL TAP CONCEPTSPrevious work has shown that natural language is unsuitablefor making the distinction between triggers (discrete events)and conditions (ongoing states) [4]. Even in a jigsaw-puzzlebased composition environment, triggers and actions can beconfused if they are not distinct [5]. Inspired by the Blocklyeditor [6] and similar environments, Jeeves blocks are sep-arated into ‘palettes’. An example of this distinction can beFig. 1. A Location trigger, with an if-block containing a location condition,and an action to capture the current locationseen in Figure 1. The trigger represents an event — a user’slocation, acquired through their smartphone’s GPS sensor, haschanged to Home. The if-block then evaluates its condition,representing whether a user is currently Home. Finally, theaction captures and stores data from the GPS sensor. Whilesuch an execution is nonsensical, it serves to illustrate thedifferent uses of smartphone sensor functionality in Jeeves.Unambiguous context-aware behaviours should be com-posed of one discrete event trigger, with an optional numberof state conditions [1], [2]. As shown in Figure 1, Jeeves,like other blocks languages, supports these constraints throughthe visual affordance of correct connections. With no external‘notches’, event triggers cannot be nested together. Multipleconditions can be nested, but only within an event trigger.III. SLIPS AND MISTAKESWe observed that Jeeves blocks supported our participantsin thinking about triggers, conditions and attributes correctlyin task completion. However, errors from both mistakes andslips resulted in obscurity and damage of mental models [7].A. From Slips To FallsIn part of a task, participants had to set a ‘Do Not Disturb’attribute to be true. Figure 2 (Right) shows that a ‘near miss’had a negative impact on their mental model of how blockscould be combined. One participant who made this slip, whenlater asked about her understanding of the ‘set attribute’ action,stated that she “couldn’t work out how to use it”, despitepreviously demonstrating a correct assumption of the action’sbehaviour. Participants learn that a block snapping into placeindicates correctness, so when this fails to happen, correctchoices are discounted and mental models break down.© AAM, 2019. This is the author’s version of the work.  It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in C&T 2019: The 9th International Conference on Communities & Technologies - Transforming Communities [https://doi.org/10.1145/3328320.3328371].Fig. 2. Left: A correct snap supports a user’s mental model. Right: A ‘near miss’ damages the mental modelFig. 3. Language ambiguity caused trigger, action and condition confusionB. Blame The NameOrganising blocks by type into palettes supports recognitionover recall. However, our participants’ inexperience with TAPcaused issues with recognition, thus they would hunt for ablock by name, regardless of its type. In one task, we askedparticipants to turn on the Bluetooth sensor when a user returnshome. Figure 3 shows two examples of participants failing tofind the appropriate ‘capture data’ action — they instead triedadjusting the sensor trigger (top), or used a sensor conditionin place of the action (bottom). When they found and used thecorrect action, they expressed doubt as to correctness.IV. REBUILDING BLOCKSHow do we rebuild a damaged mental model? Based onfeedback and observations of our study participants, we pro-pose two potential solutions, which will be incorporated intoJeeves and evaluated in a further study.Baudisch et al. [8] demonstrate their ‘drag-and-pop’ inter-action, supporting drag-and-drop on large displays, wherebyan icon’s compatible drop locations are drawn towards it. Weare currently considering a similar solution we call ‘lock-onblocks’, which will visually suggest compatible locations fordragged blocks, resolving certain mistakes, as well as reducingslips. As suggested by one participant, simple highlighting ofcorrect locations for a dragged block may also be sufficient.The question “Does that block live there?” was raised byone of our participants, and echoed in various forms by others.Forgetting where to find correct blocks, many would search inthe ‘conditions’ palette for an action. Conversely, they wouldsometimes look to actions for functionality provided by acondition. Rodriguez et al. demonstrated that block categorynames can have a significant effect on perceived usability [9].As a flexible solution, we propose that having the user click ona particular drop location would automatically switch them tothe relevant palette, guiding their search. This could reinforcehow triggers, actions and conditions combine.V. CONCLUSIONWe propose that blocks can support TAP, but care must betaken to reinforce fragile assumptions when they are correct.REFERENCES[1] B. Ur, E. McManus, M. Pak Yong Ho, and M. L. Littman, “Practicaltrigger-action programming in the smart home,” in Proc. 32nd Annu.ACM Conf. Human factors in computing systems, 2014, pp. 803–812.[2] J. Huang and M. Cakmak, “Supporting mental model accuracy in trigger-action programming,” in Proc. 2015 ACM Int. Joint Conf. Pervasive andUbiquitous Computing, 2015, pp. 215–225.[3] D. Rough and A. Quigley, “Jeeves - A Visual Programming Environmentfor Mobile Experience Sampling,” Visual Languages and Human-CentricComputing (VL/HCC), 2015 IEEE Symp., pp. 121–129, 2015.[4] M. Garcı´a-Herranz, P. Haya, and X. Alama´n, “Towards a UbiquitousEndUser Programming System for Smart Spaces,” Journal of UniversalComputer Science, vol. 16, no. 12, pp. 1633–1649, 2010.[5] Y. Dahl and R. M. Svendsen, “End-user composition interfaces for smartenvironments: A preliminary study of usability factors,” in Lecture Notesin Computer Science, vol. 6770 LNCS, no. 2, 2011, pp. 118–127.[6] N. Fraser, “Ten things we’ve learned from Blockly,” in 2015 IEEE Blocksand Beyond Workshop (Blocks and Beyond), Oct 2015, pp. 49–50.[7] D. A. Norman, “Design rules based on analyses of human error,”Commun. ACM, vol. 26, no. 4, pp. 254–258, Apr. 1983.[8] P. Baudisch, E. Cutrell, D. Robbins, M. Czerwinski, P. Tandler, B. Bed-erson, A. Zierlinger, and M. Push, “Drag-and-Pop and Drag-and-Pick:Techniques for accessing remote screen content on touch- and pen-operated systems,” Proc. INTERACT ’03, pp. 64–57, 2003.[9] F. J. Rodrı´guez, K. M. Price, J. Isaac, K. E. Boyer, and C. Gardner-Mccune, “How Block Categories Affect Learner Satisfaction with aBlock-Based Programming Interface.”

Trigger-Action Programming (TAP) has been shown to support end-users' rule-based mental models of context-aware applications. However, when desired behaviours increase in complexity, this can lead to ambiguity that confuses events, states, and how they can be combined in meaningful ways. Blocks programming could provide a solution, through constrained editing of visual triggers, conditions and actions. We observed slips and mistakes by users performing TAP with Jeeves, our domain-specific blocks environment, and propose solutions.<br/

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TAPping into mental models with blocks

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