=Paper=
{{Paper
|id=None
|storemode=property
|title=Generating Consistent Universal Controllers for Web-Service-enabled Appliances
|pdfUrl=https://ceur-ws.org/Vol-787/paper6.pdf
|volume=Vol-787
}}
==Generating Consistent Universal Controllers for Web-Service-enabled Appliances==
https://ceur-ws.org/Vol-787/paper6.pdf
Modiquitous 2011 Proceedings
Generating consistent universal controllers for
Web-Service-enabled appliances
Marius Feldmann, Thomas Springer, Alexander Schill
Technische Universität Dresden
Fakultät Informatik
Professur Rechnernetze
Germany
{marius.feldmann, thomas.springer, alexander.schill}@tu-dresden.de
ABSTRACT universal control application for a mobile device or a
Today, an increasing number of home and office appliances Web-based universal control application. If a new device
that we interact with contain embedded Web Servers. (DVB-T device) is added to the device infrastructure, a user
Making available Web Services for remote access to their interface has to be made available dynamically within the
functionality is just a small step. In this paper, we present a two universal control applications. Developing these user
multi-platform, model-based generation approach enabling interfaces for various target platforms usually tends to
efficient and low-cost development of interactive constitute a time consuming and expensive task.
applications for accessing Web-Service-enabled appliances.
The results are not stand-alone, monolithic elements of
software but are capable of being integrated into a
consistent host application ad-hoc during runtime. Thus, a
heterogeneous and dynamic infrastructure of appliances
from different manufacturers can be accessed via single
control applications. The approach has been proven to be
applicable for generating interactive applications for
various target platforms including mobile devices.
Keywords
Web Services, Model-based User Interface Generation,
Dynamic Service Infrastructures Figure 1. Sketch of the home appliance scenario
In order to solve these problems, this paper presents an
INTRODUCTION AND MOTIVATION
approach to generate the user interfaces of the
Web Services are software components offering their
Web-Service-enabled appliances fully automatically from
functionalities via a well-defined interface. This interface is
functional interface descriptions. Due to the fact that
described by a functional interface description language
without further input, the generation result would be of low
such as the Web Service Description Language (WSDL).
quality, so called Service annotations [8] are applied as
Nowadays, Web Services are an accepted and widely used
platform independent modeling approach for defining user
means for offering remote functionalities. Various tools are
interfaces.
available for managing the whole lifecycle of Web Services
starting from creating, via testing, to deploying and The results of the generation chain named interactive
managing them. However, the field of developing user components can be embedded in the universal control
interfaces for Web Services has not been covered in a applications dynamically during runtime. Without stopping
satisfactory manner yet. Though some approaches have this application, they appear in their navigation menu and
been specified during the last years enabling the can directly be used to remote control the appropriate
development of user interfaces for static Web Service device. Due to the possibility to parameterize the
infrastructures, no approach exists that makes it possible to generation of interactive components by using layout and
extend an interactive application fully automatically style descriptions, they can be visually adapted to different
depending on the associated set of Web Services the appearances of the embedding universal control
application interacts with. The necessity for such an applications. Thus, a consistent visual representation is
interactive application becomes obvious in the case of the achieved.
selected use case: Within an automated home, a set of The remainder of this paper is structured as follows. In the
appliances can be controlled via a universal control second section an overview of the state of the art in the
application available on different platforms. In the sketched addressed domain is provided. The third section defines the
scenario in Figure 1, three appliances (Light Control concept of interactive components and points out their
System, Music Control System and a Router) can be central characteristics. In the fourth section the assumed
accessed via their offered Web Services by using either a development approach is described. The fifth section
M. Feldmann, T. Springer, A. Schill: Generating consistent universal controllers for Web-Service-enabled 39
appliances. Proc. of 1st International Workshop on Model-based Interactive Ubiquitous System 2011, Pisa, Italy,
June 13, 2011, http://ceur-ws.org/Vol-787
Modiquitous 2011 Proceedings
introduces the steps for generating interactive components As soon as an interactive component is physically available
from the results of the development approach. The sixth on a target device, it runs through the following steps:
section describes the technical realization of the mentioned 1. Registration: The interactive component
appliance control scenario and an end user study applied communicates the information needed for its execution
using the prototypical implementation. The paper is to the host application. The registration information
concluded by a summary and outlook on future work. covers:
STATE OF THE ART a. Identifier: In order to identify a component and to
Creating user interfaces for home appliances is a topic replace old versions on a target platform, a unique
covered in the HCI community already for years (e.g. [3]). identifier is assigned to every interactive
As well the specific goal to create consistent user interfaces component.
for controlling different devices has been addressed [4].
However, these approaches do not focus in any way on b. Component Dependencies: An interactive
Web-Service-enabled appliances. Thus, the possibility to component may demand functionality that has to
generate user interfaces from functional interface be provided by the host application. This includes
descriptions is not discussed. The only approach exploring for example functionality to determine the current
Web Services in the field of universal appliance control geolocation or specific data storage facilities.
applications exploits a task-driven development approach c. Input-/Output-Data: An interactive component
to create consistent user interfaces [5]. Though the may interact with a host application via
efficiency of this approach may be increased by using exchanging data. To identify the data needed as
Service annotations [6], it still takes various manual steps input and returned as output, references to data
to develop a user interface for different target platforms. described within the associated functional
Furthermore, the resulting user interfaces cannot be interface description is used.
embedded automatically into a host application during d. Context information: Every interactive
runtime. Extending the focused research and development component may be generated for a concrete usage
field to ad-hoc UI generation approaches for context such as a specific language, a specific
Web-Service-based interactive applications, we discovered target platform or a selected geographical location.
a set of ten approaches. They usually take either a A context description is expressed as a set of
functional interface description or additionally Service context type and value information.
annotations as input and create stand-alone markup-based
UIs as output. An example for this category of approaches e. Information for visualization purposes: An
is described in [7]. The results have a low quality and do interactive component is included dynamically
not address the generation of consistent UIs enabling the into the navigation menu of a host application so
interaction with various underlying Web Services as it is that a user can activate it. For visualizing the
demanded within the home appliance scenario. component, data such as a label text or an icon is
communicated to the host application.
To summarize our efforts, we realized an intensive
state-of-the-art analysis searching for approaches that make If a host application accepts the registration
it possible to generate automatically user interfaces for information and fulfills the requirements (thus it can
Service-based interactive applications and that create offer the necessary components (b) and the appropriate
results which can be included ad-hoc into a running host input data (c)), the registration is successful. If the
application. To the best of our knowledge, no comparable interactive component is not registered successfully, it
approach like the one presented in this paper exists. is removed from the host application.
INTERACTIVE COMPONENTS
2. Activation: After an interactive component has been
Interactive components are a domain-specific solution for registered successfully and the current application
user interfaces of Service-based interactive applications. context conforms to the context the component is
Due to their characteristics, they solve the identified intended for, the component can be activated by a user.
problems of dynamic integration of ad-hoc generated user The host application hands over the input parameters
interfaces into a hosting interactive application. demanded by the interactive component during the
registration procedure.
Interactive components contain all information necessary
for registration purposes within a host application. They 3. Usage: After a successful activation of the interactive
offer a user interface for providing input values and component, a user can input data via the user interface
displaying output values of Web Service operations and and invoke remote Web Service operations. The
contain all information needed for enabling the interaction operation results are being visualized in the user
of a human user with a remote Web Service. After an interface.
interactive component has been generated, it is transmitted 4. Deactivation: The interactive component can be
to a host application (such as the universal appliance deactivated at any time by the host application or the
control application) via an application specific directory user. After the deactivation has been triggered, its user
Service. interface is not visible anymore. During deactivation of
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Modiquitous 2011 Proceedings
an interactive component, it returns the output data 2. Bundling: Renders it possible to merge the user
specified during the registration process to the host interfaces of different operations into one user
application. interface. Furthermore, the view for input and output
We have specified a Meta-model named Service-based of one operation might be merged in one view.
Interactive Component Model (SBIC) for representing 3. Provided by Host: Marks an input parameter of a
interactive components during the generation process. The Service operation as input to the interactive component
structure of the model is sketched in Figure 2. The SBIC provided by the host application.
has been developed as a model representing an interactive 4. Returned to Host: Marks output parameters to be
component in a way close to a runtime representation. returned to the host application when the interactive
Thus, a model-to-code transformation mapping a SBIC component is deactivated.
instance to a platform specific interactive component can
be implemented with little effort. 5. Component Dependency: Defines dependencies to
functionalities the host application has to provide.
Besides the registration information, the SBIC describes the
structure, navigation flow and data flow of the user 6. Initial Operations: A subset of the operations defined
interface. Furthermore, it contains layout and design in a functional interface description may be marked as
information that is weaved into the model during the initial. These operations can be accessed directly from
generation process. Thus, the layout and design of a the host application. Every initial operation is an entry
generated interactive component can be adapted to the point to activate the interactive component. After
layout and design of a host application. activating it, the user interface for the appropriate
initial operation is visualized.
DEVELOPMENT APPROACH
As aforementioned in the state-of-the-art analysis, the In order to specify these annotations, an authoring tool
development of Service-based interactive applications for named Interactive Component Editor (ICE) [2] has been
various target platforms is currently a time-consuming task created. One of the views of the ICE is shown in Figure 3.
involving huge manual effort. Our approach is After importing one or more functional interface
characterized by the novel idea to only use Service descriptions into the tool, the tree structure of these
annotations for modeling user interfaces. As the descriptions is visualized. The nodes on the various levels
state-of-the-art does not offer any Service annotation model (Service, operation, input/output parameters, data types) of
enabling the specification of application-specific aspects the tree representation can be included into the modeling of
such as navigation or data flows, we introduced new the interactive component.
annotation types. The screenshot in Figure 3 shows various navigation flows
To not reinvent the wheel, these types were introduced into and data flows in a specific editor view during modeling an
the annotation model originating from the ServFace project interactive component for a DVB-T device. The editor
[8]. Besides others, the following annotation types have makes it possible to specify any of the annotations defined
been specified and included into an extension of the within the ServFace project and of the abovementioned
ServFace annotation model: extensions. Thus, a full featured development approach has
been created enabling the model-based specification of
1. Navigation Flow: Enables the possibility to define a interactive components solely with annotated functional
navigation flow between the user interfaces derived interface descriptions.
from different Service operations. With every specified
navigation flow, a data flow may be associated. After the modeling has been realized, the resulting
annotations are serialized to a file and transferred to a
remote annotation repository.
GENERATION APPROACH
The generation of interactive components is triggered on
demand once an interactive component has to be embedded
into a host application. In the case of the automated home
scenario, the generation chain is activated as soon as a new
device and thus a new annotated Web Service appears in
the home infrastructure. Due to the usage of platform
independent Meta-models and the platform specific
parameterization of the generation approach, it can be
reused for various target platforms and different host
applications. The platform and host specific parameters
have to be provided only once for every host application.
The target specification can be reused during the generation
of each interactive component that should be embedded
Figure 2. Structure of interactive component Meta-model into this host application.
The generation chain is summarized in Figure 4.
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Modiquitous 2011 Proceedings
Figure 3. Screenshot of the Interactive Component Editor
In a first step, the functional interface description and the For instantiating the ISF, the ASM instance is traversed. By
annotation file fetched from an annotation repository are default for every Service operation one container for all
parsed and merged together into a common model. For this input parameters and one container for all output
purpose the Annotated Service Model (ASM) has been parameters are derived and embedded into the ISF instance.
developed. It enables the representation of all ServFace This default behavior may be modified by annotations of
annotations and the mentioned extensions. An ASM the Bundling type (see previous section).
instance contains, on the one hand, the tree representation In a next step, appropriate interactors are derived from all
of the functional interface description with the different input and output parameters passed during traversing of the
hierarchies (Service, operation, input/output parameters, ASM instance. They are embedded into the containers
data types) and, on the other hand, the annotations created in the previous step.
referencing a subset of the tree’s nodes. This subset has
been determined during the development approach applied As the selected interactors are described within the ISF
e.g. by using the ICE. using platform specific vocabulary, this step is
parameterized by a set of inference rules which determine
After the ASM has been instantiated, a basic structure of which interactor should be selected under which condition.
the user interface with all its interactors is inferred in a first Besides the data types of an input or output parameter, the
model-to-model transformation step. For representing the decision depends particularly on the set of annotations
structure of the UI, a domain-specific model named referencing this parameter.
Intermediate Service Frontend Model (ISF) adapted to the
generation chain has been developed.
Figure 4. Generating interactive components from annotated functional interface descriptions
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Modiquitous 2011 Proceedings
Figure 5. Usage of the generation approach within the home appliance scenario
In a second model-to-model transformation step, an 4. Using platform-specific model-to-code transformations
instance of the SBIC Meta-model mentioned above is (named platform adapters) for all desired target
created from the ISF instance. Just as the transformation platforms, the SBIC instance is transformed to
steps before, the implementation of this step can be reused platform specific interactive components.
for various target platforms due to the parameterization of 5. These components are forwarded to a repository that is
the transformation. The provided parameters contain checked in fixed intervals by the used universal control
especially layout and design information for adapting the applications for updates.
appearance of the interactive component to the appearance
of a host application. This information can be made 6. As soon as a new interactive component is available
available a-priori and updated as soon as the layout and within the repository, it is downloaded to the target
design of the host application is modified. platform and registered in the universal control
application.
Finally, every SBIC instance is transformed to a platform
specific interactive component that can be made available 7. After a successful registration of an interactive
via a component repository to a host application. For every component it can be used to interact with the remote
supported platform a model-to-code transformation has to Web Service thus enabling device control.
be provided that takes an SBIC instance as input and REALIZATION AND EVALUATION
returns a packaged and deployable interactive component The approach has been implemented and evaluated using
as output. two heterogeneous target platforms as shown in Figure 5.
The described generation chain builds the core of the home As proof-of-concept for mobile devices, a universal control
appliance scenario introduced above. Figure 5 shows the application and a platform adapter for the smartphone
different steps used to make interactive components platform Android has been realized and as proof-of-concept
available in different universal control applications. for Web applications, the same parts of software have been
implemented using the Apache Wicket framework. The
The approach runs through the following seven steps: repository for devices has been realized as a simple
1. A device (e.g. a DVB-T device) is newly introduced relational database. As technology for the repository for
into the infrastructure of Web-Service-enabled interactive components Subversion (SVN) was used. SVN
appliances. As soon as it is switched on, it is registered has the central advantage that no additional mechanism for
by transmitting the Uniform Resource Identifier (URI) versioning of interactive components had to be introduced.
of its functional interface description plus a reference Figure 6 shows a screenshot of the prototypically
to an annotation file to a device repository. implemented Web-based universal control application. As
2. The device repository is monitored by a specific it is depicted in the figure, interactive components are
system component named Activator. As soon as this embedded once they are registered in this application into
component detects a new device registration, it its navigation menu shown on the left side. The initial
forwards the functional interface description operations (see fourth section) of each interactive
referenced by the URI plus the annotation file to the component are displayed by a navigation option each. As
generation chain described above. soon as a user selects one of these options, the appropriate
3. The generation chain parses the functional interface user interface is displayed in the center of the Web page.
description and the annotation file and transforms it
first to an ISF and then to a SBIC instance.
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Figure 6. Prototype for the Web-based universal control application
The approach has been evaluated based on the prototypical REFERENCES
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