Challenging Documentation Practices for Interactions inNatural User Interfaces

Bashar AltakrouriAmbient Computing Group

Institute of TelematicsUniversity ofLubeck

Lubeck, Germanyaltakrouri@itm.uni-luebeck.de

Andreas SchraderAmbient Computing Group

Institute of TelematicsUniversity of Lubeck

Lubeck, Germanyschrader@itm.uni-luebeck.de

ABSTRACTDozens of novel natural interaction techniques are proposedevery year to enrich interactive eco-systems with multitouchgestures, motion gestures, full body in motion, etc. Wepresent a novel investigation of the community’s applied doc-umentation practices for Natural User Interfaces (NUI). Ourinvestigation includes analyzing a survey targeted at NUI de-signers and a large sample of recently published multitouchand motion-based interaction papers. To the best of ourknowledge, this paper is the first to offer a close investiga-tion of this kind. The results reveal that good NUI documen-tation practices are rare and largely compromised. Thus, weargue that engineering interactive systems for large-scale dy-namic runtime deployment of existing interaction techniquesis greatly challenged.

Author KeywordsNatural User Interfaces (NUI); Gesture Interfaces; MotionInterfaces; HCI modeling; HCI documentation; HCI sharing.

ACM Classification KeywordsH.5.m. Information Interfaces and Presentation (e.g., HCI):Miscellaneous; H.5.2 Information interfaces and presentation(e.g., HCI): User Interfaces

INTRODUCTIONCalls arise to explore new potential in designing for the wholebody in motion as part of the NUI paradigm [3][4], to fa-cilitate users’ interactions with real-world pervasive ecosys-tems (ambient spaces). In the literature, different definitionsof NUI [6] were elaborated, which mostly refer to the user’snatural abilities, practices, and activities to control interactivesystems. Devised from Wachs et al. [10], interactions withNUI can be shortly defined as voice-based and kinetic-basedinteractions. Kinetic-based interactions are mostly causedand characterized by motion and movement activities, rang-ing from pointing, clicking, grasping, walking, etc. [2]

Workshop on Large-scale and model-based Interactive Systems: Approaches andChallenges, June 23 2015, Duisburg, Germany.Copyright c© 2015 for the individual papers by the papers’ authors. Copyingpermitted only for private and academic purposes. This volume is published andcopyrighted by its editors.

Herein, we focus on a subset of Kinetic-based interactions,namely multitouch- and motion-based interactions. In the lastdecade, touch and motion enabled technologies found theirway commercially and became widely accessible to the enduser, in various application domains such as gaming (e.g.,motion-controlled active play by Microsoft Kinect1 or the Wiisystem2), data browsing, navigation scenarios (e.g., tilting forscrolling photos as in iOS3 and Android4 devices) and manymore.

Despite the immense progress and success in different ap-plication domains, interactive environments will pose addi-tional significant challenges to the design, engineering anddeployment of NUI technologies. Considering user hetero-geneity, e.g. due to aging and demographic change (”come-as-you-are” paradigm), user mobility to unknown environ-mental settings at design time (interaction context) and spon-taneous construction of interactive environments in-situ atruntime, the isolated design of natural interface devices willnot be sufficient any more, regardless of the quality andnaturalness of the proposed interaction scheme per se. Intheir work, Altakrouri and Schrader [2] proposed a shift to-wards completely dynamic on-the-fly ensembles of interac-tion techniques at runtime. The Interaction Ensembles ap-proach is defined as ”Multiple interaction modalities (i.e., in-teraction plugins) from different devices are tailored at run-time to adapt the available interaction resources and possibil-ities to the user’s physical abilities, needs, and context” [2].A shift of this kind imposes new dissemination, deployment,and adaptation requirements for engineering interaction tech-niques and interactive systems for NUI. Precisely for thosereasons, better understanding and analysis of the practiceddocumentation habits of interaction techniques for NUI playsa major role to bridge the possible gaps between designinginteraction techniques and engineering interactive systems.

In this paper, we present a novel investigation of the com-munity’s applied documentation practices for interactions inNUI. We believe that an investigation of this kind is essentialto understand some of the challenges for engineering inter-active systems in ambient spaces and setting proper interac-1http://www.microsoft.com/en-us/kinectforwindows/, latest accesson 25.03.2015.2http://www.nintendo.com/wii, latest access on 25.03.2015.3http://www.apple.com/ios/, latest access on 25.03.2015.4http://www.android.com/, latest access on 25.03.2015.

tion dissemination guidelines, where interactions are becom-ing increasingly dynamic, adaptive and multi-modal.

Our novel investigation is concluded by analyzing a surveytargeted at NUI designers and a large sample of recently pub-lished multitouch and motion-based interaction papers. Al-though limited in scale, we believe that this investigationopens the door for important open research issues for the CHIand EICS community around this problem domain.

In this paper, the term documentation is used to capture theway an interaction technique is defined and described by theinteraction designer (i.e. developer). Principally, documen-tation refers to any written material, visual clues, animatedclues, formal description models and languages, etc, used todescribe or disseminate the developed interaction. The liter-ature covers various approaches to describe touch-based in-teractions. An extensive review on those approaches is out ofthe scope of this paper. In their work about formal descrip-tions for multitouch interactions, Hamon et al. [5] analyzedthe expressiveness of various user interface description lan-guage (an extension to [8]) and suggested the ICO formalismfor modeling multitouch interactions. Principally, modelingincludes data description, state representation, event repre-sentation, timing, concurrent behavior, dynamic instantiation,etc. Recently, Altakrouri et al. [1] targeted their effort todescribe the movement aspects of motion-based gestures andthe physical context (i.e., abilities and disabilities) of the user.

Documenting interaction technique is relevant for the correctexecution of interactions by end users, the preservation oftechnique by designers, the accumulation of knowledge forthe community, and the engineering of interactive systems.We argue that documenting interactions should be treated asan important resource of context information about the in-teraction technique, which can be also utilized by interactivesystems for various reasons. For instance, filtering relevantinteraction techniques at runtime in response to the user’sphysical context (e.g., disabilities) as in the Interaction En-semble approach mentioned above.

Better understanding of the currently applied documenta-tion practices does not only reveal the current dissemina-tion strategies but also triggers possible needs for new tools,guidelines, and systems that improve those practices and ulti-mately bridge the gap between the design of single interactiontechniques and the development of interactive systems.

In this paper we will substantiate the following main contri-butions and findings:

• We present a number of observations regarding the NUI de-signers’ most commonly applied documentation choices,most importantly, documentation frequency and mediatype of choice.

• We unveil that NUI documentation is largely underesti-mated and compromised by NUI designers due to the lackof adequate documentation tools, absence of documenta-tion standards, and irregularity of documentation habits.

METHODOLOGYOur study included two investigation areas: (1) analyzing atailored survey targeted at NUI designers and (2) coding andanalyzing a large sample of recently published multitouch andmotion-based interaction papers. In this section, we first out-line our approach before we present the results in the follow-ing section.

Survey on NUI documentationThe first step in our review was to capture a snapshot on thecurrent most employed practices for NUI documentation bycarrying out an online survey. The survey aimed to partiallycharacterize a number of designers’ documentation practices,including: (1) The adoption level and frequency of documen-tation practices and standards in design and development ofNUI; (2) The designers’ satisfaction with their practiced NUIdocumentation habits; (3) The needs for new documentationtools and methods; (4) The commonly used documentationmethods, tools, and media types; and (5) The perceived im-portance of documentation for sharing, acceptance, user ex-perience, and correctness.

The survey was targeted at both NUI designers (i.e. NUI de-velopers) and users, it was split into two sections accordingly.In this paper, we only focus and report about the designersection, which contained a total sum of 11 different multiplechoice and likert scale questions. The survey was bound toa maximum completion time of 3 minutes to maximize thenumber of voluntary participations. The survey included anintroductory section where the notion of NUI, specially formultitouch- and motion-based interfaces, as well as the pur-pose of the survey were introduced.

The survey was distributed online through specialized HCImailing lists (including BCS-HCI run by the British Com-puter Society Human-Computer Interaction Group5), ubiqui-tous computing mailing lists (including Ukubinet-announcerun by the Imperial College London6 and announce-ments@ubicomp.org7), Lubeck university mailing lists, andsocial networks (i.e. Facebook, Twitter, and ResearchGate).The survey was open for participation for about 3 weeks.

Analyzing the interaction publications landscapeThe second step in our review intended to capture a closerlook at the published work in the area of interaction tech-niques. In order to find out how the community expresses,documents, and shares interaction techniques, we have de-cided to base our investigation on a collection of the mostrecent ACM published work under the ACM classification(H.5.2 Information Interfaces and Presentation: User Inter-faces - Input devices and strategies) for the years 2012 and

5https://www.jiscmail.ac.uk/cgi-bin/webadmin?A0=bcs-hci, latestaccess on 25.03.2015.6https://mailman.ic.ac.uk/mailman/listinfo/ukubinet-announce, lat-est access on 25.03.2015.7http://mail.ubicomp.org/mailman/listinfo/announcements ubicomp.org,latest access on 25.03.2015.

2013 (until 22.08.2013). Out of 518 total papers in this cate-gory, we manually coded and analyzed a total sum of 93 pa-pers that matched one of two categories: (1) papers present-ing novel interaction techniques; (2) papers applying or an-alyzing existing interaction techniques in various scenarios.Our filtering criteria excluded all none touch or none motiongesture papers (as considered out of the focus of this inves-tigation), video papers (as those papers don’t have enoughspace to cover the interaction technique and only convey verylimited aspects of the work), and duplicated paper entries (ifthe same work was presented in multiple venues but with dif-ferent contribution size, e.g., work-in-progress papers, shortpapers, full papers). In the case of duplication, the latest andlongest contribution was considered. Our aim was not to con-duct a complete and detailed review of all published papers.Instead, we aimed at providing a snapshot at the most recentpublished work as a living example of the current practiceddocumentation habits.

Our analysis and classification are based on the publishedpaper and any corresponding material directly mentioned,linked, or attached with the published work (e.g., many pub-lished papers have also videos attached within the ACM li-brary, or links to external resources). Other materials out ofthe aforementioned criteria were considered hidden and werenot included in the study, such as in application help menusor offline accessible manuals.

The papers were coded based on four main aspects: Type- gesture types discussed in the paper including multitouchand motion gestures; Still - used still media types to doc-ument and describe the gesture including text, images, andsketches; Animated - used animated media types to documentand describe the gesture including videos, animations, per-sonal walkthrough, and onscreen walkthrough; and finallyAuthoring - reported or used authoring and documentationtools and formal languages. Our main goal of this analysiswas to highlight general practices and habits rather than fo-cusing on a particular paper title or the authors. Hence, wereference the reviewed papers by the unique identification key(ACM ID) instead of the papers’ full title or author names.

RESULTS AND OBSERVATIONSIn this section, we present the results for each of our inves-tigation areas. We have supported the data with a number ofgeneral observations to enhance the readability of the results.The observations are numbered and marked with an abbrevia-tion to the corresponding section (D: Designer survey sectionand P: Papers analysis section).

SurveyA total of 332 anonymous individual responses wererecorded, split into 267 NUI users (80% of the total respon-dents) and 65 NUI designers (20% of the total respondents).

The designer respondents are split to 11 expert designers, 14professional designers, 28 competent designers, 10 advancedbeginners, and finally 2 novice designers. This categorizationis based on an explicit survey question about expertise self-assessment.

We have applied Kruskal Wallis test to identify any statisti-cally significant differences among expertise groups. In mostcases, no statistical differences amongst groups were foundunless explicitly mentioned in the text.

Observation - D1: Small majority of NUI designers are sat-isfied with their current documentation practices: 57% of thedesigners responded positively to a question on the satisfac-tion with their current documentation habits.

Observation - D2: Only a small minority of NUI designerspractice NUI documentation continuously: Figure 1 showshow often the designer respondents document designed NUI,independent of form or documentation type. The figure re-veals that the majority of the respondents practice documen-tation either sometimes (42%) or frequently (38%). Merelysmall minority of designers (14%) practice documentationregularly. Statistically significant difference was identifiedamong expertise (H(4) = 13.466, p = 0.009) with a mean rankof 43.93 for proficient, 33.75 for competent, 32.91 for expert,18.70 for advanced beginner, and 18.0 for novice designers.Higher mean ranks indicate a more frequent documentationpractice.

Figure 1. Practicing NUI Documentation and Complying with Stan-dards

Observation - D3: The vast majority of NUI designers neveror rarely apply documentation standards: One interesting as-pect in this survey is to highlight the designers’ habits to ap-ply standard documentation approaches, as shown in Figure1. The survey unveils that about half of the respondents neverapply any documentation standards and merely a third did onrare occasions. Small number of respondents apply documen-tation standards either sometimes (14%) or frequently (3%).

Observation - D4: The majority of NUI designers indicateda lack of NUI documentation tools and methods: The respon-dents answered positively (66%) when asked whether there isa lack of NUI documentation methods and tools available forthem to use.

Observation - D5: NUI are mostly documented using text,pictures, sketches, and videos respectively: Another goal ofthe survey was to identify the dominant media types used bydesigners to document interaction techniques. Figure 2 il-lustrates the distribution of used NUI documentation mediatypes by designers. Text is the most used medium to describe

and document NUI. Still visual documentation records (i.e.pictures and sketches) follow next. Moreover, animated vi-sual records come fourth. Additionally, audio and formal lan-guages come last with very low percentages.

Figure 2. Medium for Documentation

Observation - D6: NUI are rarely documented using formal-ized languages: Figure 2 also shows clearly designers don’tfollow formalizations as a documentation media type.

Observation - D7: The most ranked importance of NUI docu-mentation is acknowledged for sharing NUI, followed by userexperience: Figure 3 illustrates the designers’ perceived im-portance of NUI documentation for sharing, experience, ac-ceptance, and correctness. The vast majority of respondersscored documentation as a very important (45%) or an im-portant (37%) factor for a successful sharing of NUI. Re-garding user experience, the majority of respondents scoredthe documentation as an important (48%) or a very impor-tant (11%) factor respectively. Moreover, designers scoredNUI documentation for user acceptance as very important(14%), important (40%), moderate (25%), and of little im-portance (18%). Merely 3% negatively scored documentationas unimportant for the user acceptance. Finally, the majorityof respondents scored documentation as either an important(40%) or very important (26%) factor for the correctness ofNUI execution. Approximately one third of the respondentsscored documentation as moderate or of little importance forcorrectness.

Scientific publicationsFigure 4 illustrates the complete classification of the analyzedpapers based on the previously presented methodology. Pa-pers that satisfy the conditions are distinguished with a cod-

Figure 3. The Designers’ Perceived Importance of Documentation forAcceptance, Correctness, Experience, and Sharing of NUI

ing mark as shown in the figure. The analyzed papers weremotion (51%) and touch based (68%) interaction papers (notethat a paper may fall into more than one category).

Observation - P1: NUI in publications are mostly docu-mented using text, sketches, and pictures respectively: As ex-pected, figure 4 shows that text descriptions as a medium fordocumenting interaction techniques is used in all of the pa-pers that we have reviewed. Sketches (59%) come secondwith a very close match with the designer survey in Figure 2.Pictures (53%) come third, slightly lower than in the designersurvey.

Moreover, personal walkthrough is reported by 16% (the de-veloper introduces the interaction technique to other develop-ers or users by demonstration). Videos are reported by 11%.This percentage matches the survey’s results (Figure 2). Inresearch papers, mentioning and linking to video content isusually neither required nor critical for the acceptance of theresearch paper. Hence, videos related material to the tech-nique are often hidden. The use of animations is reportedonly once. This matches to a large extend the designer surveyresults in Figure 2. On the other hand, other media types suchas onscreen walkthrough are hardly used.

Observation - P2: NUI in publications are never documentedusing formalized languages or interaction authoring tools:To our expectations, none of the papers reported or usedlanguages (including notations and formalisms) or interac-tion authoring tools (including gesture authoring tools). Fi-nally, we found no statistical difference between the two mainaforementioned analyzed groups of papers.

DISCUSSIONIn this section, we present a number of interesting aspectsregarding NUI documentation practices and possible impacton designing and engineering interactive systems.

Documentation habits: Ignorance or underestimation?Our results show that the majority of the designer respon-dents are satisfied with their current NUI documentation prac-tices (D1). Nonetheless, this satisfaction is not necessarilyreflected on the quality and extend of applied documentationpractices (D2, D3). Those observations unveil that NUI docu-mentation is generally an underestimated or ignored problemby interaction designers and developers.

Clearly, the NUI paradigm vastly grows in terms of the num-ber of interaction proposed, the diversity of interaction types,involved body parts, involved actions, etc. [3][4][8]. Greatadvancements, in terms of innovation and usability evalua-tion, of this type of interaction are usually proposed and pre-sented at various venues and conferences such as ACM CHI(Human Factors in Computing Systems) and UIST (User In-terfaces Software and Technology). Despite this effort, someresearchers believe that very little effort is actually targeted toimprove the reliability of systems offering and adoption thesekinds of novel interaction techniques [8].

Soon the lack of adequate interaction documentation and dis-semination will lead to challenge the design and engineer-ing of interactive systems. Documentation can be used to

Figure 4. ACM Multitouch and Motion based Interaction Papers Review - Interaction Documentation Practices and Habits Analysis for The Years 2012and 2013 (until 22.08.2013)

extract information about the type of movements involvedin the interaction, involved body parts, adequate interactionexecution, etc. The absence of such information will nec-essarily lead to burden the deployment of interaction tech-niques in automated interactive systems, especially processessuch as context acquisition, reasoning, interaction filtering,etc. are greatly hindered. The absence of documentation in-evitably challenges analyzing the proposed interaction tech-niques. For instance, requirement analysis can be greatlycompromised, analyzing physical requirements for NUI usersis not possible, or correctly reproduce or extend a particu-lar interaction techniques becomes an extremely challengingtask.

Documentation types and methodsThe results show that various media types are used by design-ers for documentation. From one hand, designers reportedthat the most used media types for documenting NUI aretext, pictures, sketches, and videos respectively (D5). Theacademic paper investigation on the other hand shows text,sketches, and pictures respectively used in the analyzed pa-pers (P1). Despite the aforementioned difference, it is clearlyvisible that designers rarely use formalized languages or ap-proaches as a documentation medium (D3, D6, P2). Formal-ized description of NUI are an important mean to documentvarious aspects on the interaction to insure integrity and cor-rectness of execution, and the possibility of replicability.

Designers are not in favor of formal languages and audio.This can be due to the complexity of language learning, andthe complexity of describing movements respectively. Whilstformalized languages can be hard to learn and apply, theyare often used in different fields for documenting movements.Formalized languages have a clear benefit to preserve andtransfer the technique to other designers without endanger-ing the originality and vital aspects of the technique. Using

the currently applied media such as text, pictures, sketches,and videos may lead easily to losing parts of the movements,overly complicated descriptions, losing timing information,etc.

In fact, according to Navarre et al. [8], formal interfacesdescription languages support interaction at the development(e.g., prototyping) as well as the operation phase, while con-ventional empirical or semiformal techniques lack to provideadequate and sufficient insights about the interaction (e.g.,comparing two design options with respect to the reliabilityof the human-system cooperation).

The notion of movement is of particular importance for Ki-netic Interactions, as it resides at the core of this type of inter-actions. Movement documentation is a very relevant and gen-erally a very unresting problem for many fields such as dancechoreography, movement rehabilitation, motion recognitionand analysis, and human movement simulation. Accord-ing to Kahol et al. [7], having such languages and notationsfeatures three main qualities: facilitate teaching and learn-ing of movement styles, permit the writing of universally-understood scores of movement, and provide a universal lan-guage to communicate movements. Nonetheless, Kahol etal. [7] still acknowledge the lack of a formalized languagesand notations of generic motion, matching our investigationresults (especially D4). We share the same viewpoint as in[8], lacking adequate and formalized documentation lead in-evitably to increase the gap between the design and (commer-cial) deployment of developed interaction techniques.

The importance of documentationDesigners recognize the importance of documentation for theusers’ experience, the acceptance of NUI techniques, andcorrectness of use. The most important use of documenta-tion is for sharing NUI techniques (D7). Sharing is particu-

larly important for different purposes such as communicatingNUI to other peer designers, improving NUI functionality byother designers, adopting NUI techniques in various interac-tive eco-systems, and reaching user audience. Even thoughdesigners recognized these important roles, their documenta-tion practices appear generally ignorant to this importance.

Documentation challenges in future ambient spacesSo far we have discussed the current NUI documentationpractices, but the shift towards future ambient spaces imposesnew requirements, and challenges the current practices.

This type of interactive systems aims at avoiding mismatchproblems between user’s needs and device’s offers, by em-ploying the best matching interactions to the given context,hence the user independence (acceptability by permitting cus-tomizability) and usability qualities required by Wachs et al.[10] are inherently enhanced. Pruvost et al. [9] noted thatinteraction environments are becoming increasingly hetero-geneous and dynamic, hence they are no longer static andclosed; the interaction context is becoming increasingly morecomplex; and, increasing adaptability is required for sustain-able utility and usability.

Current NUI documentation practices, as discussed in this pa-per, are greatly challenged by such a system. The currentdocumentation practices and strategies are not adequate andfail to meet the challenge of dynamically created documen-tation for interaction ensembles. Interactions are currentlyego-centric and designed in isolations, so is the documenta-tion. Such isolation implies a complete absence of informa-tion about the interaction’s behavior as part of an ensemble ina dynamically changing eco-system.

FUTURE WORKAs part of our research roadmap, we will continue to ex-plore this field by (1) extending our investigation to study thedifferences and similarities between NUI documentation inacademic and commercial settings (as in motion-based andtouch-based application market initiatives); (2) extending ouranalysis to include NUI users and their learning habits; and(3) extending our ongoing work on a dedicated tool for docu-menting NUI

CONCLUSIONWe have presented an investigation on the applied practicesand habits to document and share developed interaction tech-niques. The analysis included: (1) an online exploratory sur-vey on documenting Natural User Interfaces (NUI) answeredby 64 designer; and, (2) coding and analyzing a sample of93 recently ACM published multitouch and motion-based in-teraction papers. Our study reveals that good documentationpractices are rare and largely compromised. Our survey re-veals that there is a lack of documentation tools, methods, andformal languages; designers almost never follow or apply anydocumentation standards; and designers never use availableinteraction authoring tools. Hence, the creation of a collec-tive long lasting interaction heritage remains unachievable.Moreover, the gap between developing and rightly dissem-inating interaction techniques increases. Thus, engineering

interactive systems for large-scale dynamic runtime deploy-ment of existing and future interaction techniques is greatlychallenged.

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