Towards Gesture-based Process Modeling on Multi-Touch Devices [original]

Towards Gesture-based Process Modeling

on Multi-Touch Devices

Jens Kolb, Benjamin Rudner and Manfred Reichert

Institute of Databases and Information Systems

Ulm University, Germany

{jens.kolb,benjamin.rudner,manfred.reichert}@uni-ulm.de

http://www.uni-ulm.de/dbis

Abstract. Contemporary tools for business process modeling use menu-

based interfaces for visualizing process models and interacting with them.

However, pure menu-based interactions have been optimized for applica-

tions running on desktop computers and are limited regarding their use

on multi-touch devices. At the same time, the increasing distribution

of mobile devices in business life as well as their multi-touch capabil-

ities offer promising perspectives for intuitively defining and adapting

business process models. Additionally, multi-touch tables could improve

collaborative business process modeling based on natural gestures and

interactions. In this paper we present the results of an experiment in

which we investigate the way users model business processes with multi-

touch devices. Furthermore, a core gesture set is suggested enabling the

easy definition and adaption of business process models on these devices.

Overall, gesture-based process modeling and multi-touch devices allow

for new ways of (collaborative) business process modeling.

Key words: process modeling, gestures, user-centered process model-

ing, multi-touch application

1 Introduction

Multi-touch devices have been increasingly used in companies during the last

years and have become more and more useful for the daily work of business peo-

ple. Multi-touch devices used in companies range from smartphones and tablets

to multi-touch tables and walls. Obviously, screen size affects both mobility and

application areas. While smartphones are primarily used for mobile communi-

cation (e.g., mailing and information retrieval), tablets and multi-touch tables

are applied for enabling collaborative tasks (e.g., joint editing of a business doc-

ument). Consequently, multi-touch devices may be applied to business process

modeling as well. In particular, portable multi-touch devices can be used to

capture and model business processes while interviewing process participants.

Multi-touch devices with larger screens (e.g., multi-touch tables), in turn, can

be used to collaboratively model, discuss and change business processes [1]. How-

ever, traditional process modeling tools have not been designed with multi-touch

devices in mind and do not take their specific properties (e.g., small screen size)

2 Jens Kolb, Benjamin Rudner and Manfred Reichert

and interaction possibilities (e.g., gesture-based interaction) into account [2, 3].

In this paper we introduce a set of gestures to easily and intuitively model

business processes using multi-touch devices. This gesture set enables process

designers to define, visualize and adapt business processes in an intuitive and

comprehensible way. The focus of the paper is on the introduction of this core ges-

ture set, and less on a concrete user interface design. The suggested core gesture

set is applicable to all screen sizes of multi-touch devices. It has been developed

in the context of the proView1project [4], which aims at user-centered pro-

cess management. This includes techniques enabling personalized process model

visualizations (e.g., process views [5, 6]) as well as intuitive process model repre-

sentations (e.g., diagrams and trees [7]). Gesture-based modeling complements

this work with sophisticated and intuitive concepts for interacting with process

designers.

The remainder of this paper is structured as follows: Section 2 gives background

information on multi-touch applications and summarizes the abstract modeling

operations to be supported by the gesture set. Section 3 presents the results of an

experiment we conducted to analyze how users interact with multi-touch devices

and which kind of gestures they are using to model and change processes. These

results provide the foundation of the core gesture set introduced in Section 4.

Finally, Section 5 concludes the paper with a short summary and outlook.

2 Background

This section describes background information needed for the understanding of

this paper. Section 2.1 introduces general interaction concepts, which can be used

to interact with an application on a multi-touch device. Section 2.2 then lists

common characteristics of multi-touch applications. Finally, Section 2.3 presents

a core function set required for modeling and adapting business processes.

2.1 Multi-Touch Interaction Concepts

Generally, users may interact in different ways with a multi-touch application.

First, concepts used in the context of conventional desktop applications may

be applied to multi-touch application as well; e.g., menu-based interactions use

menus and toolbars to provide available functions to users. As an advantage,

this concept allows users to easily explore the application when searching for

a specific function. However, displaying menus and toolbars requires space on

the screen, which is limited on devices with small screens (e.g., smartphones).

Hence, menu-based interaction should primarily be used for multi-touch appli-

cations running on larger screens.

Gesture-based interaction, in turn, uses gestures for selecting functions of the

multi-touch application as well as for interacting with them. Thereby a (multi-

touch) gesture constitutes a movement of one or more fingers on the screen of

1http://www.uni-ulm.de/in/iui-dbis/forschung/projekte/proview-project.html

Towards Gesture-based Process Modeling on Multi-Touch Devices 3

the multi-touch device. This movement is then recognized and interpreted by

the application. For example, in a slideshow of pictures the wipe gesture (i.e.,

wiping with one finger from right to left) can be used to display the next picture.

Generally, gestures can be categorized into physical gestures and symbolic ges-

tures [8]. Physical gestures manipulate the virtual objects on the screen directly,

e.g., by dragging a virtual element on the screen. Symbolic gestures, in turn, are

related to the function to be executed (e.g., drawing a plus to add an object).

As opposed to menu-based interactions, gestures do not require any space on

the screen in order to display menus or other graphical elements. However, as

a barrier for their application, users do not always know which functions are

supported by a multi-touch application and with which gestures they can be

selected. The latter is especially crucial for novices and unexperienced users of

the multi-touch application. Usually, this problem is addressed through a tu-

torial provided the first time the user starts the application. Finally, a hybrid

interaction based on both menu- and gesture-based interactions can be realized.

For example, a menu bar may be displayed at the top or bottom of the screen

offering the most important functions. Additionally, well-known gestures may be

supported, e.g., the above mentioned wipe gesture.

2.2 Characteristics of Multi-Touch Applications

Besides their interaction concepts multi-touch applications—or to be more pre-

cise their multi-touch capabilities—can be described through six properties.

C1 (Screen Occlusion): The user interface design of a multi-touch applica-

tion should consider that users directly interact with the application, but might

cover screen areas with their hand [9]. For example, dragging an object from the

top-left corner of a tablet to its bottom-right corner will be a difficult task if

large parts of the screen are covered by the user’s hand.

C2 (Handling Precision): Conventional desktop applications, require a mouse

pointer to interact with them. This pointer scales with the screen resolution in

order to ensure high precision of the interactions. In multi-touch applications, in

turn, the ’interaction device’ is the user’s finger [10]. As opposed to the mouse

pointer, a finger does not scale up or down when changing screen sizes. Accord-

ingly, the handling precision of a multi-touch application changes with the size

of an object the user has to touch. Studies have shown that an object should

have a size of 11.52 mm or more to have a hit probability of at least 95% [11].

Regarding multi-touch process modeling, it will be crucial to achieve a high han-

dling precision.

C3 (Fatigue of Extremities): When using a computer mouse, usually, the

hand does not move a lot. Typically, the arm lays on the table and the mouse

is moved with the fingers to reach the corners of the screen with the mouse

pointer. Interacting with multi-touch applications, in turn, frequently requires

the movement of the whole arm. Further, the arm does not lay on a table, but

has to be hovered in the air during the interaction with the multi-touch applica-

tion [12]. Obviously, the degree of movement strongly depends on the screen size.

4 Jens Kolb, Benjamin Rudner and Manfred Reichert

C4 (Number of Supported Fingers): Compared to conventional desktop

applications with a mouse pointer, a multi-touch application typically supports

more than one touch point. Generally, the maximum of touch points an applica-

tion supports is limited through the underlying hardware and operation system.

For example, Apples iPad distinguishes between 11 touch points (i.e., fingers)

[13]. While this number is sufficient for single user applications, multi-user ap-

plications should be able to even support more touch points, e.g., in order to

allow for the concurrent modeling of processes on a multi-touch table.

C5 (Number of Concurrent Users): Multi-touch applications may be con-

currently used by multiple users. Obviously, the degree of concurrency is limited

by the screen size. While concurrent interactions with a tablet would effect each

other, concurrent use of an application on a multi-touch table (e.g., joint editing

or modeling) might improve the way of working [14]. Especially in the context

of concurrent process modeling, this should be exploited, particularly in process

management projects involving multiple modelers [15].

C6 (Usage of Common Interaction Concepts): As known from conven-

tional desktop applications, there are interaction concepts representing de-facto

standards. Examples include the menu bar on the top of the application window

or File as first entry of such a menu bar. Such recurrent patterns help users to

intuitively interact with applications. The same applies to multi-touch applica-

tions and especially gesture-based interactions; e.g., the pinch gesture is typically

used for zooming. However, there are only few gestures that have been used in a

consistent manner so far. Therefore, [16] suggests a gesture dictionary with the

intention that different applications show similar behavior in connection with a

specific gesture.

The introduced characteristics of multi-touch devices show their wide range

of possible applications. Obviously, these characteristics should be taken into

account when designing gestures for business process modeling.

2.3 Required Functions for Modeling Business Processes

This section introduces a core function set required to model and change pro-

cesses. This function set is derived from the change patterns presented in [17, 18].

In the context of this paper we assume that process models are well-structured

and are based on an activity-centric modeling language. Furthermore, a process

model is displayed to process designers by using advanced layout algorithms,

i.e., the process designer cannot position single process elements arbitrarily on

the screen. Finally, an initial process model consists of a start and an end node

connected through a control-flow edge. Based on modeling functions F1-F8, as

introduced in the following, the (multi-touch) application ensures that the ele-

ments of a process model are connected.

Function F1 (Insert Activity) inserts a single activity into a process model be-

tween two existing nodes. F2 (Insert Surrounding Block) encloses a process frag-

ment with an XOR (AND) block, i.e., an XOR (AND) split with corresponding

XOR (AND) join gateway. The enclosed process fragment may be also “empty”

Towards Gesture-based Process Modeling on Multi-Touch Devices 5

leading to the creation of an XOR (AND) block having one “empty” branch.

Function F3 (Insert Branch) extends an existing XOR (AND) block with an

empty branch between the splitting and joining gateway.

Function F4 (Renaming Element) changes the name of a process element, e.g.,

an activity or data element. To delete process elements, function F5 (Delete

Element) can be applied. The process element may be an activity, a data ele-

ment, or a gateway. Comparable to F1, function F6 (Insert Data Element) adds

a new data element to the process model. This data element, in turn, can be

connected to activities using function F7 (Insert Data Edge). Finally, function

F8 (Extract/Inline Sub-process) extracts a sub-process based on a selected set

of activities or inlines this sub-process [19]. This function is especially required

when modeling complex process hierarchies. An overview of the core function

set is given in Table 1.

Core Function Set

F1 Insert Activity F5 Delete Element

F2 Insert Surrounding Block F6 Insert Data Element

F3 Insert Branch F7 Insert Data Edge

F4 Renaming Element F8 Extract/Inline Sub-process

Table 1: Core Function Set

In this paper, we restrict ourselves to this core function set, which provides

elementary functions required to model and adapt processes. Obviously, addi-

tional functions are required for a sophisticated process modeling tool (e.g., to

specify attributes or to undo/redo modeling steps).

3 An Experiment on Multi-Touch Process Modeling

Experimental research in the context of business process management has al-

ready shown promising results regarding user-centric process support [20, 21,

22, 23]. In our research, we conducted, a user experiment on multi-touch process

modeling before developing a corresponding gesture set. Using the Goal Defi-

nition Template as presented in [24], the goal of the experiment is defined as

follows:

Analyze multi-touch process modeling interaction

for the purpose of evaluating

with respect to their intuitive usage

from the point of view of the researchers and developers

in the context of students and research assistants.

6 Jens Kolb, Benjamin Rudner and Manfred Reichert

Taking this goal definition, our experiment evaluates multi-touch interactions

applied by users—or to be more precise by students and research assistants—

when modeling and changing processes on multi-touch devices. The results of

this experiment are then used to develop a consistent set of modeling gestures

covering the core process modeling functions introduced in Section 2.3. Based

on this goal definition, the following hypothesis is derived:

Users intuitively use multi-touch gestures when modeling and changing

process models on multi-touch devices.

Section 3.1 refines the goal and explains the experiment setting. Section 3.2

discusses the results of the experiment.

3.1 Experiment Setting

The experiment is designed as a multi-test within object study [24], i.e., having

two groups of participants and one object. Students (as first group) do not have

a broad background in process modeling and process management, whereas the

second group consists of research assistants being more experienced with process

modeling. Furthermore, the experiment is divided into two parts. In the first one,

demographic and background information of the participants is collected (i.e.,

gender, experience with multi-touch devices, profession). In the second part of

the experiment, each participant has to modify an existing process model (i.e.,

object) in eight different steps. Each step includes a description explaining to

participants what they have to do in order to perform the respective process

modeling task (cf. Section 2.3). For example, step “Think of a way to create a

new activity between Make Up Package and the XOR Branch” can be accom-

plished using core function F1 (Insert Activity).

The response variable of our experiment is the interaction category used to per-

form the required change of the process model. Therefore, for each step the

variable can have one of the following values: picture-based,gesture-based, or

menu-based interaction.

As instrumentation of the experiment, an Apple iPad and the multi-touch draw-

ing application Doodle Buddy [25] is used. For each step, this application displays

an image to the participant. On the image, a process model is shown serving as

starting point for the model change to be conducted in the respective step. Fur-

thermore, the aforementioned textual explanation is displayed in this context.

Finger movements of participants are captured through lines overlaying the im-

age (cf. Figure 1). Additionally, the gesture is captured through a video camera.

The latter records the screen of the device as well as the hands of the partici-

pant and their movements. Furthermore, participants are asked to think aloud

about what they are doing and what they are thinking about [26]. This informa-

tion is used for classifying and interpreting results afterwards (cf. Section 3.2).

Furthermore, the supervisor of the experiment stays in the same room as the

participant, motivates him or her to think aloud, and provides assistance in case

of emerging questions.

Towards Gesture-based Process Modeling on Multi-Touch Devices 7

3.2 Analysis and Results

26 participants attended the experiment. Table 2 summarizes background infor-

mation on them. It is worth mentioning that the number of participants being

experienced with multi-touch devices (e.g., smartphones) and participants not

using multi-touch devices is almost equal.

Gender Profession Handedness Multi-Touch

Experience

26 Participants 19 Male 17 Students 25 Right 14 Yes

7 Female 9 Res. Assist. 1 Left 12 No

Table 2: Participants’ Background

We classify the interactions a participant applies in the context of a concrete

modeling step into three interaction categories. Note that this classification is

accomplished by two persons and is therefore a subjective measurement. As basis

of this measurement, we choose the drawing overlaying the image of the respec-

tive modeling step as well as the video capturing the actual movement of the

participant’s hand.

The first category groups gesture-based interactions. This kind of interaction

uses simple movements on the multi-touch screen changing the process model

(as physical gestures described in Section 2.1). Figure 1a exemplarily shows a

gesture-based interaction applied to insert an XOR block surrounding a par-

ticular process fragment in a process model. In this scenario, the participant

moves two fingers simultaneously up and down in order to insert the surround-

ing block.

The second category comprises picture-based interactions, i.e., all interactions

drawing a realistic representation of the final result expected from the applica-

tion of the respective modeling function (as symbolic gestures, cf. Section 2.1).

Figure 1b shows an example of this category.

The third category captures all interactions presuming the presence of a menu

bar or context menu. Figure 1c exemplarily shows the result of a participant who

is drawing a toolbar at the top of the screen and is dragging & dropping the re-

quired process elements on the depicted process model. This category, therefore,

covers menu-based interactions.

Figure 2 summarizes the results of the experiment and visualizes the distri-

bution of the interaction categories. On the x-axis, each step of the experiment

is represented through its corresponding function. The y-axis, in turn, shows the

number of participants using interactions from a specific category.

Obviously, there is no predominant interaction concept covering all process mod-

eling functions. However, for certain functions one can observe a clear preference

for a specific interaction concept. Function F8 (Extract/Inline Sub-process), for

example, is applied by 73% of the participants by using gesture-based inter-

action. For other functions (e.g., F2 (Insert Surrounding Block)), however, no

8 Jens Kolb, Benjamin Rudner and Manfred Reichert

(a) Gesture-based Interaction (b) Picture-based Interaction

Fig. 1: Interaction Categories of the Experiment

dominating interaction can be identified. Hence, multiple interaction concepts

should be provided to optimally support different user groups and users in ap-

plying respective functions.

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

Picture-based

Gesture-based

Menu-based

Fig. 2: Distribution of Interaction Categories

When drilling down the results, some insights into differences of the interac-

tions applied by the two groups of participants can be identified. Analyzing the

influence of multi-touch experience, for example, shows that experienced partic-

ipants use gesture-based interactions more often than picture- and menu-based

Towards Gesture-based Process Modeling on Multi-Touch Devices 9

interactions (cf. Figure 3a). By contrast, unexperienced participants more often

tend to predominantly use picture-based interactions, but do hardly use menus

(cf. Figure 3b). Probably, this can be explained by the fact that unexperienced

participants are unaware of common interaction concepts as provided by multi-

touch devices (cf. Section 2.2).

Comparing the results of the two gender groups (cf. Figures 3c+3d), female par-

ticipants predominantly use picture-based interactions. Moreover, none of the

female participants uses gesture-based interactions when applying function F6

(Insert Data Element). Male participants, in turn, show a clear preference for

gesture-based interactions.

Finally, comparing the results of the professions, participants with low experience

on process modeling (i.e., students) slightly prefer gesture-based interactions (cf.

Figure 3f). Opposed to this, participants having modeling experience (i.e., re-

search assistants) do not clearly prefer a specific interaction except for function

F8 (cf. Figure 3e). Overall, here no clear distinction can be made.

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

(a) Experience=yes

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

Picture-based

Gesture-based

Menu-based

(b) Experience=no

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

Picture-based

Gesture-based

Menu-based

(d) Gender=female

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

(e) Profession=Res.Assist.

20%

40%

60%

80%

100%

F1 F2 F3 F4 F5 F6 F7 F8

Picture-based

Gesture-based

Menu-based

(f) Profession=Student

Fig. 3: Experiment Results

10 Jens Kolb, Benjamin Rudner and Manfred Reichert

A B

(a) Wipe to Right

A B

Data

(b) Scroll the Menu

A B

Data

Task

Fig. 4: Gesture for Inserting New Elements

Note that the results of our experiment are only to a certain degree representative

due to the rather low number of participants and the chosen experiment setting.

Nevertheless, it can be concluded that process modeling experience does not in-

fluence the way how processes are modeled on multi-touch devices. By contrast,

being experienced with multi-touch devices affects the way of modeling processes

on them. This can be explained by the non-availability of standardized gestures

on multi-touch devices (cf. Section 2). Therefore, when developing a multi-touch

application, its target group should be taken into account as well; e.g., it might

be relevant to know whether members of the target group use their own devices

or multi-touch devices are handed out to them.

In the following, we focus on end-users being experienced with multi-touch de-

vices, and propose a core gesture set enabling intuitive process modeling.

4 A Core Gesture Set for Process Modeling

Taking into account the results of our experiment, we propose a core gesture set

for modeling and adapting processes. In this context, we have to cope with the

existing trade-off between common interaction concepts provided by multi-touch

devices and the results of our experiment. Our goal is to provide an appropriate

gesture set suited for modeling and adapting processes on multi-touch devices.

4.1 Core Gesture Set

Our experiment shows that users prefer a menu-based interaction when adding

new elements to a process model (cf. Figure 2). Therefore our core gesture set

includes a slider menu enabling the insertion of activities, data elements, and

surrounding control-flow blocks (cf. functions F1, F2, F6). To trigger the slider

menu, users wipe with their finger from an existing process element right to

insert the new element at the respective position (cf. Figure 4a). Following this,

the slider menu appears at the position where the user releases his finger from

the surface of the multi-touch device. Through up and down movements in the

slider menu, the required process element can be chosen. For example, to insert

Towards Gesture-based Process Modeling on Multi-Touch Devices 11

an element, the user taps on the respective icon in the slider menu (cf. Figure 4c);

afterwards the slider menu disappears and the element is inserted. Obviously,

when inserting a surrounding control-flow block, a second position needs to be

selected for adding the corresponding join gateway. For this purpose, the pro-

cess model editor shows valid positions in the process model where the joining

gateway may be inserted; the user then chooses a position by tapping on it. To

provide more sophisticated user support when inserting a control-flow block that

surrounds an existing process fragment, abstractions in terms of process views

are useful, i.e., abstracting the process model to a simpler one only comprising

those activities being relevant for the insertion of a join gateway [5].

The ordering of the process elements depicted in the slider menu can be opti-

mized by considering their usage frequency. For example, inserting an activity

might be more often required compared to the insertion of a surrounding control-

flow block. Therefore, the respective function should be positioned on a “central”

position in the slider menu that can be quickly accessed.

Another core gesture allows inserting new edges into a process model (cf.

Figure 5a). Since we presume a block-structured modeling approach with fixed

layout, in general, only two types of edges need to be “manually” added: data

edges and edges connecting split and join gateways to add “empty” branches.

For example, the user has to draw a line with his finger from the splitting to the

joining gateway in order to insert an “empty” branch between them (i.e., F3).

A C

Data

(a) Insert Edges

A Z

B C

A Z

B C

A Z

(b) Extract/Inline Sub-process

Fig. 5: Gesture to Insert Data Edges and Extract/Inline Sub-processes

To insert a data edge, in turn, the user has to draw a line between the activity

and the respective data element or vice versa (i.e., F7). The direction of the data

edge indicates whether it represents a read or write access of the activity on the

data element. When inserting a data edge, the gesture set supports users by

suggesting a target element (see the left of Figure 5a). If the target element is

the desired one the user can lift his finger and the edge will be automatically

12 Jens Kolb, Benjamin Rudner and Manfred Reichert

completed and inserted. Note that this gesture complies with our experiment

results since for both functions (i.e., F3 and F7) the majority of participants

prefer gesture-based interactions.

To extract or inline a sub-process (i.e., function F8), a two-handed gesture is

introduced. The user pushes the start and end element of the process fragment to

be extracted into a sub-process activity (Figure 5b). While pushing the elements

towards each other, the movement needs to be animated to give direct feedback

to the user. After completing the gesture, the new sub-process model has to be

linked to the respective sub-process activity. The resulting sub-process can then

be displayed through a double tap gesture. To inline a sub-process, in turn, the

user pulls the sides of the activity representing the sub-process apart. When

pulling the sides of this activity apart, the sub-process appears and is inlined

into the process model again. Note that this gesture also matches the results of

our experiment in which a majority of 73% of the participants use gesture-based

interaction in the context of function F8.

Though 62% of the participants of the experiment use gesture-based interaction

to rename a process element (i.e., free-hand writing on the screen), most mobile

applications provide an on-screen keyboard for inserting or modifying text on

multi-touch devices. The keyboard is hidden most of the time to save screen space

and is displayed only when the user wants to add or modify text. To comply with

common interaction (de-facto) standards on multi-touch devices, in our gesture

set, function F4 (Renaming Element) can be activated through tapping on a

process element. Afterwards the keyboard appears and the user may modify the

text. After confirming the modified text, the keyboard disappears.

Fig. 6: Delete Element Gesture

Finally, the majority of participants delete process elements using gesture-

based interactions. For realizing this function, a gesture crossing out the element

to be deleted is suggested (cf. Figure 6). Generally, different variants for realiz-

ing this gesture could be envisioned (e.g., drawing two crossing lines or one line

from bottom-left to top-right). Regarding our core gesture set, the user draws a

connected zigzag-line on the respective element. Generally, this is more accurate

regarding recognition compared to the drawing of two separate lines.

Towards Gesture-based Process Modeling on Multi-Touch Devices 13

5 Summary and Outlook

In this paper, we presented the results of a first experiment we performed to

investigate how users model processes on multi-touch devices in a natural and

intuitive way. Experiment results indicate that gestures are useful for interacting

with process modeling functions, but that for some functions menus are preferred

when editing process models. Based on our experiment results as well as com-

mon interaction concepts of multi-touch applications a core gesture set has been

suggested. This gesture set provides the basis for process modeling tools offer-

ing new ways of gesture-based process modeling and providing a high degree of

usability. Note that it is no good idea to migrate existing modeling tools, which

were designed for desktop computers, straight forward to multi-touch devices

since this would affect the usability. The gesture set developed is independent

from a concrete device type (e.g., table, tablet or smartphone), but has to be

extended with gestures for supportive functions (e.g., undo/redo, copy, paste) in

order to use it in a production environment.

As next step a proof-of-concept prototype will be developed. Using this modeling

application, further experiments will be conducted to evaluate usability of the

developed core gesture set and to elaborate emerging opportunities for modeling

processes on multi-touch devices.

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