MODELLING USER INTERACTIONS IN WEB SERVICE-BASED

BUSINESS PROCESSES

Antonio Pintus

CRS4, Loc. Pixinamanna Edificio 1, Pula (CA), Italy

Dipartimento di Informatica e Matematica, Università di Cagliari, Via Ospedale 72, Cagliari, Italy

Fabio Paternò, Carmen Santoro

CNR-ISTI, Via Moruzzi 1, Pisa, Italy

Keywords: User Interface Modelling, Model-Based Design, Task Models, Business Processes, Web services.

Abstract: This paper presents a methodology that defines a model-based approach in composing User Interfaces for

Business Processes based on Web service technology. The core concepts of the methodology are

represented by an integration of modern task model notations developed in the HCI area, such as

ConcurTaskTrees, with a mainstream notation for Business Process modelling (BPMN) developed in the

workflow/business process area. The main advantage is to obtain thorough support in designing complex

interactive business applications able to flexibly compose Web services and obtain meaningful associated

user interfaces which can be not only Web interfaces but also extended to a multi-modal fruition. The

proposed methodology allows a collaborative work between business process modellers and user interface

modellers remaining open to iterative refinements. In this paper we also briefly compare the considered

notations and discuss an example application of the proposed method.

1 INTRODUCTION

Business Process solutions enable enterprises to

consolidate and optimize their business operations

and to gain competitive advantage in the fast

evolving global market. Business process modelling

is the activity of representing enterprise processes.

In particular, the Business Process Modelling

Notation (BPMN) is a standard for business process

modelling, based on a flowcharting technique, able

to represent complex process semantics. With a

broad adoption of Web service technology, business

process management solutions (and workflow

systems in general) started to include Web service

support as a natural component in processes

specification.

Model-based user interface design has mainly

focused on how to obtain user interface

implementations from user interface description

languages or task models. Business process models

have addressed a different topic: how to organize

workflows using business. Business process

notations do not seem suitable to specify user

interfaces for those process units that require user

interactions nor they provide a modelling

methodology for them. Also, Web service

specifications and standards do not include a

formalism to describe and associate user interfaces

related to services, so they have to be composed and

authored from scratch depending on platform, media

and programming languages constraint. This

becomes even more complicated in case of SOA

applications based on Web services and designed as

Business Processes. Thus, it is important to

investigate novel solutions able to integrate business

process-oriented approaches with approaches

coming from the HCI field, such as task models.

They can lead to new methodologies for designing

customizable systems supporting business processes,

which benefit from model-driven user interface

design to support business process management

environments with adaptable, process-specific and

task-specific interfaces. There is a general agreement

on the abstraction layers relevant for interactive

systems, like the CAMELEON Reference

Framework (Calvary, 2003), and there has been a

175

Pintus A., PaternÃš F. and Santoro C.

MODELLING USER INTERACTIONS IN WEB SERVICE-BASED BUSINESS PROCESSES.

DOI: 10.5220/0002774401750180

In Proceedings of the 6th International Conference on Web Information Systems and Technology (WEBIST 2010), page

ISBN: 978-989-674-025-2

considerable amount of work on how to support

transformations across such layers in order to

address multi-device environments, i.e. (Mori,

2004). In this case the generated user interfaces

adapt to the interaction resources available in the

target devices. Thus, the methodology proposed in

this paper can also support derivations of user

interfaces for various types of devices (desktop,

mobile, vocal, ...), which can be used depending on

the current context and task.

In this paper we propose an integrated approach

which combines BPMN notation for business

process modelling with ConcurTaskTrees (CTT) for

task modelling, to fulfil the design of user interfaces

for interactive business processes based on Web

services. Lastly, some conclusions along with

indications for future work are provided.

2 RELATED WORK

The relations between HCI task modelling and

business process modelling are stimulating

increasing interest in deriving user interfaces for

human-based activities in business processes.

In (Traetteberg, 1999) the integration of task

modelling with workflow modelling languages is

motivated from a general point of view, making the

assumptions that workflow models can provide a

useful context for task modelling at different levels

since they essentially face the same domain and, in

particular, low-level workflow activities can be

considered high-level tasks in task models, hence a

task model can be viewed as a refinement of a

workflow model from the perspective of a particular

user role. However, differently from our approach,

this work is not much focused on business processes

based on Web Services, which raise specific design

issues.

In (Zhao, 2007), information inference from a

business process specification is used within a

model-based approach where automatic user

interface generation is achieved through a set of

transformations that exploit the definition of several

heuristic rules to obtain task models directly from

business processes. However, in this work, the issue

of how to transform a task model into a UI structure

is a decision of the UI designer, while in our

approach we make provision for several rules and

guidelines to move in a semi-automatic way from

task models to final UIs. In (Guerrero, 2008) a user

interface modelling approach in the context of

workflows is proposed but it does not use the BPMN

notation. Other works have focused on rapid

prototyping of low-fidelity user interfaces mock-ups

using business process models as a starting point:

(Sukaviriya, 2007) and (Pontico, 2006) highlight the

need of integrating UI aspects in business process

models and the fact that business notations, such as

BPMN alone, are not suitable to analyze user

activities because user interactions are disjointed

throughout the process and stress that a mixed user-

centred approach can lead to several advantages in

eGoverment applications. Moreover, an interesting

work (Sousa, 2008b) has proposed a model-driven

approach in aligning business processes, expressed

using BPMN, with user interfaces, in which

assumptions made on associations between elements

of those models are exploited to automatically

transform business process models into user

interface models to then complete the user interface

development cycle. Therefore, also the latter work

mentioned assumes the concept that the information

contained in business processes are not sufficient for

supporting the related UI design.

3 CONCURTASKTREES AND

BPMN NOTATIONS

The strong motivation of workflow systems is to

provide automatic support to organisation processes

by incorporating the rules that define how activities

should be carried out, how they should

communicate/coordinate/synchronise with each

other, and how to manage the involved information

objects while harmonising their solutions with

existing operating systems, databases, software

applications and hardware infrastructures.

Task modelling deals with similar concepts, as

its objective is to identify the activities users are

supposed to carry out in order to achieve their goals

while using an interactive system and information

contained in task models can be used to generate

effective user interfaces accordingly.

However, on the one hand workflow systems

share some concepts with task modelling, especially

when methods based on task analysis are applied to

multi-user applications, since both of them cope

with identifying roles, specifying constraints

between the activities carried out by the various

roles for accomplishing their work, the information

objects manipulated, and so on. On the other hand,

two basic differences can be identified between

them; the first one is the granularity of the

considered activities: in workflow systems the focus

is generally on entire processes at the organisational

level, which might even have a long duration,

whereas task analysis focuses more on individual

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users’ interactions with applications, which in some

cases can be almost instantaneous. The other

difference is the area in which they have been

developed: workflow systems originated in the area

of information systems, where their original aim was

to allow different users to have access to the same

information in a consistent manner, while task

analysis is basically connected with human-

computer interaction, since it provides relevant

information that can be appropriately used in the

design of user interfaces.

The Business Process Modelling Notation (BPMN),

is a visual notation for business process flows

modelling, composed of graphical elements,

semantics, attributes and properties, which visually

compose a Business Process Diagram (BPD) (OMG,

2007). It is conceived to provide a readily

understandable formalism by both business analysts

and technical developers. BPMN fits well with

Service-Oriented paradigms and Web service

technology since it can be almost finally mapped to

process execution languages (Owen, 2005) in order

to obtain an executable process from a BPMN

diagram, providing a notation for them. BPMN

supports modelling a business process flow using

activities, events, gateways for business decisions

and flow branching. Activity is a generic term in

which are included processes and sub-processes and,

when it is not possible a further decomposition, in

tasks, which are the lowest-level, atomic activity

definition that are generally executed by an end-user

and/or an application, like invoking a Web service

operation. However, the concept of task in the BPD

context focuses on what should be accomplished in

performing a task and does not specify how the task

is performed. Indeed, it does not provide any

formalism to describe all user interactions in

accomplishing a particular task when a human

intervention is needed. In this case, task modelling

from HCI could result useful to describe the user

interfaces for the interactive steps involved in the

particular human activity.

ConcurTaskTrees (Paternò, 1999) is a de facto

standard notation for task modelling, also thanks to

the availability of a number of tools that support

editing and analysis of CTT specifications. Its

combination of hierarchical structures (inherited

from Hierarchical Task Analysis) with a flexible set

of temporal operators allows designers to easily

specify complex interactive sessions.

BPMN and CTT notations share similar concepts

and, sometimes even expose similar semantics, these

similarities can lead to definition of automatic

transformations between notations, as discussed in

(Sousa, 2008a), but it is also necessary to take into

account the general lack of support of BPMN for

domain data objects, and that the CTT notation,

beside direct reference to them, offers a more

detailed view on user-applications interactions. So,

we believe that an integration between BPMN for

general business processes design and CTT in

refining the specification of user oriented tasks

achieved through the use of Web services based

applications, can be useful and suitable in defining a

methodology for related user interface design.

The BPMN Task specification includes a

TaskType attribute, where a value of Service,

Receive and Send task types can be used to specify a

Task that provides or uses some sort of service,

which could be a Web service or an automated

application, whereas User task type value denotes a

task where a human performs it with the assistance

of a software application and that type is taken into

consideration our approach.

These features can be used to describe, at a

higher-level of abstraction, a complete SOA

application based on Web service technology where:

a) Tasks which are conceived as completely

automatic activities are achieved through the

invocation of Web services operations, can be

labelled as Service or Receive or Send task types, b)

Tasks in which a human user/performer

accomplishes the task using a software application,

can be labelled as User task type. In the former case,

no human involvement or actions are expected, so

no further modelling is required. More interesting is

the latter case, in which human activities are

required to be achieved and a user interface could be

presented to the user in order to accomplish the task.

This is the case in which task modelling with CTT

helps to define in detail the conceptual model of user

interactions. On the other side, also the CTT main

concept is the Task, although different from BPMN

Task. In CTT, tasks can be used to detail activities

with different levels of granularity thanks to the

hierarchical structure of the notation which allows to

detail them and retain the ancestor's relations.

CTT supports four task categories, which

indicate to what agent the performance is allocated:

a) Abstraction: which represents complex Tasks

(with sub-tasks differently allocated); b) User:

denotes a cognitive human activity; c) Interaction:

involves a human interaction with the system; d)

Application: represents a completely automatic task

performed by the system.

4 AN INTEGRATED APPROACH

In the proposed approach we make the assumption

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177

that several business activities are performed using

Web services and that some of these activities

(Tasks) require user interactions. Then, we first

model the business process using a standard business

notation (BPMN). This is useful to identify the main

activities in the process, with large granularity, and

the Web services or their compositions that are

required to support them. Then, each main activity

in the process that requires some user interaction

becomes the root for a corresponding task model

specified using CTT and describing more in detail

how such activity should be performed (see Figure

1). In developing the task models, designers should

consider on the one hand the user requirements

elicited through interdisciplinary teams and the

available Web services, in particular their operations

and parameters. Web services can be considered

system tasks in the CTT classifications, since they

are automatically performed, and the CTT model has

to be refined until a system task for each possible

used service operation is reached.

Obviously the task model should include not

only system tasks but also interactive tasks to

describe the required user interactions and user

tasks, to indicate tasks that involve particular

internal cognitive processing by the user.

From the task model then an abstract, platform-

independent description of a user interface can be

derived. This, in turn, can be transformed into a

concrete user interface description ready for the

generation of the implementation once the target

platform is identified (i.e. XHTML, voice, Java

Swing, etc…). The main advantage of this solution

is that the business process can be supported by

users working in flexible multi-device contexts, in

which users can vary the interaction device to use,

and still receive user interfaces adapting to the

varying interaction resources.

Since a task model can imply the access to

multiple Web services, the building of the

corresponding user interface can be considered a

composition of the user interfaces associated with

each Web service. Such composition can be

performed according to various dimensions: the

abstraction level considered, the granularity of the

elements composed (interface elements or groups or

entire presentations), the user interface aspects

involved (perceivable elements, dynamic behaviour

or content), and in which phase the composition is

expected to take place (e.g. at runtime or at design

time).

When designers have to refine the task model

associated with each main interactive activity in the

BPMN model, they have to consider the Web

services to access and their operations in such a way

Figure 1: The proposed approach.

that system tasks are associated with the operations

to access. The task model is then transformed into a

MARIA (Paternò, 2009) specification: a recent

XML language that provides the possibility to

specify abstract and concrete user interface

descriptions. It overcomes limitations of previous

languages in this area because it also includes a data

model, which is useful to specify the format of the

information manipulated by user interface elements;

and an event model, which allows the description of

flexible interactions with any type of interaction

objects. It also provides support for complex

scripting and Ajax-style interactions.

In this transformation from task models into

logical user interface descriptions we also consider

the existence of user interface annotations associated

with Web services. They can be useful to provide

hints from the service developers regarding

attributes to consider when designing the user

interface of applications accessing such Web

services. For example, such hints can provide

suggestions regarding labels or icons to use rather

than those automatically generated or regarding the

type of interaction object to use for accessing the

service or regarding other aspects of the service (e.g.

its importance or criticality).

5 AN EXAMPLE APPLICATION

We clarify the proposed approach through an

example taken from a business application. The

BPMN diagram visualised in Figure 2 shows an

excerpt of the flow of cooperation occurring

between a customer and a sales representative when

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some orders have to be created by the customer and

sent to the sales manager and some business

activities are performed using Web services.

In particular, Figure 2 uses two lanes to show

that there are two basic entities/participants (or

pools) involved in the process (the Customer and the

Sales Manager), which are responsible for two

different groups of tasks. Regarding the Customer,

whenever she decides that some items have to be

bought, s/he has first to login into the system, then

s/he has to create a new order (see “Create new

order” activity in Figure 2). The latter activity

automatically triggers gathering the list of available

products. This is done through a Web Service

operation invocation associated with the “Get

available products” activity in Figure 2. Such an

output is in turn sent to another Web service

operation (associated with the “Get quotations of

products” activity, see Figure 2). In this way, it has

been specified a Web service composition. After

providing this information to the user, the customer

has the necessary information for appropriately

modifying the newly created order, by adding

further details to it (e.g. by adding/deleting items).

Figure 2: BPMN Diagram (two swimlanes: Sales Manager

and Customer.

As soon as s/he finishes to modify the order, s/he

sends it to the Sales manager, and then the Customer

can logout from the system. After some time, s/he

will receive a notification (from the Sales Manager)

about the result of her order request.

If we focus on the swimlane of the Sales

Manager, her main activity is to iteratively check

information regarding drafts that already exist within

the system. However, as soon as a new order from a

customer is received, s/he decides to handle the

newly arrived order: this means to check the type of

payment requested by the customer, and then

complete the order by also sending to the customer

the notification about the result of processing the

order.

Within these two lanes there are some activities

(Tasks) that can be further refined and specified

through suitable task models since they required a

direct user interaction. It is the case, for instance, of

the “Edit Order” activity performed by the Customer

(see Figure 3 for a refinement of this activity

represented as a CTT task model), as well as the

“Complete Order” carried out by the Sales Manager

user (see Figure 4).

Figure 3: Task model of the “Edit Order” activity

(Customer).

As shown in Figure 3, the Customer is supposed

to perform several tasks in order to edit the order.

More specifically, after having checked the list of

available quoted products, s/he can iteratively add

(and also delete) items from her current shopping

cart. In addition, s/he has also to specify the type of

payment requested for buying the items specified.

Please note that, as we mentioned before, the input

of this “Edit Order” task is actually the result of

composing two different services. In addition, please

note that the activity “Edit Order” is consistently

represented as iterative in both diagrams visualized

in Figure 2 and Figure 3 (in the BPMN diagram a

“Loop type” has been used, while in the CTT

notation an iterative task is specified).

In Figure 4 there is a refinement of the

“Complete Order” activity performed by the Sales

representative user. Depending on the type of

payment requested by the Customer, the Sales

Manager activates the concerned check, and the

system notifies him about the result of the process.

Figure 4: Task model of the “Complete Order” activity

(Sales Manager).

Then, the possibility to integrate the business

process specified in Figure 2 with the information

specified in the task models of Figure 3 and Figure 4

allows us to provide an “extended” diagram in

which the associated interactive part of the business

activity considered in the example are further

specified with CTT. Having done this, it is then

possible to derive the user interfaces associated with

the various task/activities, by transforming the

information contained in the CTT task model into an

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179

abstract description of the user interface (expressed

with MARIA XML language).

In addition, also the system-supported services

specified in the BPMN diagram can be translated

(through suitable transformations) in order to obtain

the associated abstract UI descriptions for

supporting the access to such services.

After this, and depending on the specific

platform at hand, it is possible to obtain a concrete

description which is in turn transformed into a final

user interface implemented a particular language.

6 CONCLUSIONS AND FUTURE

WORK

In this paper we present an approach to integrating

business process models with task models. The goal

is to exploit the potentialities of the two fields in

order to obtain a comprehensive approach able to

support the design of complex interactive business

applications based on Web services in which not

only them are composed together, but also their

associated user interfaces. We have also shown

some example application of the proposed method.

Future work will be dedicated to developing tool

support for this method in such a way to use a single

environment for editing integrated BPMN and CTT

specifications, which can then be used to generate

user interfaces for various type of interactive

platforms exploiting intermediate logical user

interface descriptions.

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