A VISIR lab server for the iLab Shared Architecture

Abstract

This paper describes the work done at the Carinthia University of Applied Sciences towards integrating VISIR-based labs on the iLab architecture. The Virtual Systems in Reality (VISIR) project is carried out by the Blekinge Institute of Technology, Sweden and features a platform for performing experiments in different domains.

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A VISIR Lab Server for the iLab Shared Architecture
Danilo Garbi Zutin, Michael E. Auer
Department of Systems Engineering
Carinthia University of Applied Sciences, CUAS
Villach, Austria
Ingvar Gustavsson
Electrical Engineering Department
Blekinge Institute of Technology
Ronneby, Sweden


Abstract— This paper describes the work done at the Carinthia
University of Applied Sciences towards integrating VISIR-based
labs on the iLab architecture. The Virtual Systems in Reality
(VISIR) project is carried out by the Blekinge Institute of
Technology, Sweden and features a platform for performing
experiments in different domains.
VISIR; iLab Shared Architecture; online laboratories; web
services.
I.
INTRODUCTION

The VISIR system developed by the Blekinge Institute of
Technology, Sweden provides an extraordinarily flexible
environment in which students can construct and test different
circuits. The modularity of the VISIR hardware permits for
some flexibility level concerning the resources (circuit
components and lab equipments) students have at their disposal
to construct and test circuits. Beyond this, the VISIR platform
is remarkable in the interactivity it presents to students.
Electronic circuits can be built and tested by students with a
degree of freedom normally associated with a traditional,
hands-on electronics laboratory. Integrating VISIR and iLabs
turns out to be a way to provide several users from the iLabs
community the possibility to use and/or deploy VISIR-based
online laboratories inside their existing ISA framework.
This paper will present the first results of the work carried
out at the Carinthia University of Applied Sciences in
cooperation with the Blekinge Institute of technology to
integrate the VISIR workbench as a Lab Server and client into
the iLab Shared Architecture (ISA). An introduction about
VISIR and ISA will be presented and then the actual proposed
work will be detailed.
II.
THE VISIR PROJECT

The VISIR (Virtual Systems in Reality) project was started
by the Blekinge Institute of Technology, Sweden in partnership
with National Instruments and Axiom EduTech in Sweden.
The goals of the project were to create/modify software
modules for online laboratories using open source technologies
and to set up online lab workbenches [1]. The VISIR platform
offers an online workbench where users can perform
electronics experiments. Students can wire a desired circuit and
use different laboratory equipment to test that circuit. The
experiments performed with VISIR are highly interactive and
allow a real time control of the equipment. One of the most
interesting aspects of the platform is that it features an
expandable relay switching matrix where lab instructors can
attach several components as well as whole circuits depending
on the experiments to be performed. With the help of a virtual
breadboard implemented as a VISIR client module the students
can assemble several different circuits with different
component sets available and pre-configured by the laboratory
administrator/instructor. The tasks of the lab instructors are to
add components to the library, update the components list that
specifies where the components are connected at the relay
switching matrix and update the maxlists. The possible
connections are specified in the components list.
The original VISIR online workbench offers the following
flash client modules:
•
•
•
•
•
A Breadboard for wiring circuits
Function generator, HP 33120A
Oscilloscope, Agilent 54622A
Triple Output DC Power Supply, E3631A
Digital Multi-meter, Fluke 23
The equipments used by VISIR are plug-in boards installed
in a National Instruments PXI (PCI eXtensions for
Instrumentation) chassis.
Due to the modularity and flexibility of the VISIR lab
server and client software the task of integration it within ISA
is made much less complex. More details on that will be
provided in the following sections.
III.
THE ILAB SHARED ARCHITECTURE

The iLab Shared Architecture (ISA) is a web services based
software framework that aims at providing access to online
laboratories assuming that they share some characteristics. It
distinguishes the tasks of using a specific lab that comprises
an experiment from the tasks of managing users’ accounts,
user authentication and other tasks that follow a lab session.
This clear separation of roles is one of the main advantages of
the iLab Shared Architecture. ISA does not focus in a specific
type of laboratory but provides a set of general purpose
functions for lab developers. ISA is divided into three tiers
that provide different services. These tiers are client, Service
Broker and lab server. The Service Broker is the core of the
architecture and provides user authentication, authorization,
experiment data storage and access to scheduling services. The
lab clients and lab servers are lab domain specific. Fig. 1
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depicts the iLab Shared Architecture with the distributed
services.


Figure 1. The iLab Shared Architecture

A. Scheduling

In the interactive iLabs, experiments cannot be queued for
execution as a typical lab session of such an experiment might
take several minutes to execute. Therefore, a scheduling
service had to be implemented. The scheduling service of ISA
consists of two separated Web services, the User-side
Scheduling Service (USS) and the Lab-side Scheduling (LSS).
Only the Service Broker can authenticate a user and
determine if he/she has the right to schedule a lab session. The
user uses the USS to schedule a session for a lab, based on the
available time slots published by the LSS. The LSS is
responsible for setting the policies for a specific lab and can
run with different USS’s and lab servers. The policies
mentioned might be a lab setup, etc. In order to use the ISA
scheduling services, an Online Lab must be built in a way that
scheduling for a specific user will be ensured [14].
B. Ticketing

The scenario involving an interactive experiment the level
of complexity is much higher as other services are involved in
the authentication process.
implemented in the form of ticketing. This mechanism allows
some services to issue tickets that allow the access to some
resources. A ticket coupon is the authorization item transmitted
between the services [14].
The authentication was
A typical scenario involving this mechanism would be the
following. As soon as a student logs in and is authorized to
execute an experiment, tickets are created along with a coupon
representing the collection. The coupon is passed to the lab
client. In order to connect to the lab server, the client sends the
coupon to the lab server that retrieves than the ticket with the
Service Broker. If a valid ticket is returned, the user is
authorized for the amount of time reserved to use the lab. Also
for storing the data with the ESS, a ticket coupon is passed to
the ESS, which retrieves the data storage ticket. Ticketing is
also based on Web services and must be provided by the
developer of the lab server [14].

IV. INTEGRATION OF VISIR INTO ISA

In order to allow iLab users to perform experiments with the
VISIR platform it was decided to implement a VISIR iLab lab
server taking as a basis for the development the existing Time
of Day lab server. Therefore some design requirements had to
be specified:

1. Use ISA interactive services to store experiment
results and schedule lab sessions
2. Use the original VISIR flash client, measurement and
equipment servers
3. Allow teachers/instructors to create pre-configured
experiments

By comparing VISIR and iLabs it is obvious that both have
some overlapping characteristics and services, but also
different design goals. The iLab Shared Architecture is not
focused in any specific type of experiment but rather in
providing mechanisms for the creation and maintenance of a
lab session by means of standard interfaces based in Web
Services regardless the nature of the online laboratory.
The model adopted by ISA to deliver online experiments
facilitates the practice of sharing resources (online laboratories)
without the burden to manage users from other institutions.
The VISIR Web Application and ISA adopt different
approaches to deal with authorization to use resources and with
user management.
ISA implements a ticketing mechanism to deal with
authorization to use resources. When access to a resource is
requested a ticket is issued by the domain Service Broker
registered to this specific resource. The Service Broker
redirects the user to the requested resource and forwards
credential information along with the request. These credentials
are a coupon ID, passkey and the ticket issuer GUID (Global
Unique Identifier) that the resource being accessed uses to
retrieve the ticket from the ticket issuer (Service Broker) via
the Service Broker Web services interface. This mechanism is
used by the interactive iLab shared architecture to authorize
access to distributed resources. The type of the ticket may vary
according to the resource being accessed (Experiment
execution, Manage Lab Server, etc). The ticket is an XML
document and the information contained in its payload might
vary according to the ticket type. For example, a ticket of an
experiment execution request has in it payload the following
information:
•
•
•
•
•
•
•
Experiment Storage Server Address
Start Execution Time
Experiment Duration
User Group Name
Service Broker GUID
Experiment ID
User Time Zone

In iLab group policies rather than user policies are used.
Observing the ticket payload above one notice that only the
user group information is given to the lab server, what means
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that the lab server does not know the identity of the user
executing the experiment.
The lab server, service broker and the other interactive
services from ISA should accomplish the same functionalities
that the original VISIR Web application does, that means
provide the mechanism to load the flash client and maintain the
direct communication between the client and the measurement
server. Furthermore, as detailed previously in this chapter, it
should provide the flash client with information about the
modules and components to be loaded as well as necessary
information the measurement server needs to authenticate a
client before it is allowed to request other commands. Fig. 2
depicts the overall view of the system. Basically this picture
shows the interactive services of ISA replacing the original
VISIR Web application.
Another feature provided by the VISIR Web interface is the
possibility to manage and prepare laboratory experiments that
will be available for the students. This means creating a pre-
configured profiles with a components set or a pre-assembled
circuit on the virtual breadboard for a specific laboratory
exercise. These functionalities are very specific for the VISIR
Electronics laboratory and were integrated into the lab server
management interface.
By using the iLab group policy an administration group on
the service broker was created that gives access to the
management functions and other configuration interfaces of the
VISIR Lab Server (e.g. Process Agent Self Registration,
experiment management, etc). Only users which are members
of this group have access to the management interface.
On the client side the original flash modules were used.
They add an extremely important value to the experiments
carried out with VISIR because they do embody pedagogical
aspects and resemble the real instruments’ interfaces.
The client modules are loaded by a Web application where
the user is redirected to perform the experiments. This
application retrieves the credential information from the URL
query portion and uses it to retrieve the ticket from the service
broker (if it has not been stored on the lab server database).
This Web application loads the flash modules and populates a
list with available experiment setups previously created by the
laboratory instructor.
The flash client interface with the virtual breadboard can be
seen on Fig. 3. A list with all prepared experiments is
populated. These experiments were created by the lab
instructor via the lab server administration interface and are
stored in the lab server database.
The experiment client is delivered as a Flash application
and resembles real instruments used in a real laboratory. Each
instrument is implemented as a Flash module and can be
dynamically loaded as the instruments are needed. A
JavaScript enabled browser loads the Flash client and passes
several parameters to the client. Some of these parameters
determine the Flash modules to be loaded, the components
available in the components bin and circuits implemented on
the breadboard. When one of the available experiments is
selected by the student, the flash modules are reloaded and the
the desired components to be loaded in the components bin is
passed to the flash application via flashvars.
CONCLUSION
The VISIR platform for electronics experiments provides a
highly flexible online workbench as circuits can be built and
tested in a similar way as in traditional hands on laboratories.
Due to that reason we believed that providing a VISIR iLab lab
server could bring valuable assets to the iLab Shared
Architecture. In the other side, this approach would allow iLab
users to take advantages with the use of VISIR and foster
collaboration.


Figure 2. VISIR as an iLab Lab Server
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Figure 3. The VISIR Lab Client

The iLabs Shared Architecture was built based on the
philosophy that each institution or university willing to use
Online Laboratories hosted in other institutions should be
responsible for their own users. This responsibility should not
be delegated to the institution hosting the labs or even to the
Online Lab owner. Therefore, it is desirable that each
institution have its own Service Broker, although, it might not
make sense to have a Service Broker if someone intends to
have only one lab server. Beyond these issues that concern the
philosophy of ISA, there are absolutely no technical restrictions
or limitations against other practices.
Due to the advantages that ISA provides we decided to
pursue this idea to integrate a VISIR lab Server and make
VISIR experiments available to ISA users.
Moreover, remote systems can be very useful when applied
to solutions involving the often substantial costs of transporting
people or equipment. Different institutes and schools could
share experiments and knowledge in a collaborative manner
that parallels real-life working conditions. Also, by using
remote solutions, it is possible for institutions with more
limited financial resources to take advantages of expensive
equipment installed at other institutions by means of a
cooperative network of remote systems. From that perspective,
users, educators and students could more efficiently take
advantage of the use of online labs if these are available inside
of a common framework, that means, being deployed by means
of standard interfaces.

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