Christer Rindeb
ack, Rune Gustavsson
Blekinge Institute of Technology, School of Engineering
P.o Box 520, SE37235 Ronneby, Sweden
Trust, trustworthiness, trust management, e-services.
Designing trustworthy e-services is a challenge currently undertaken by many actors concerned with the de-
velopment of online applications. Many problems have been identified but a unified approach towards the
process of engineering trustworthy e-services doesn’t yet exist. This paper introduces a principled approach to
deal with trust solutions in e-services based on a concern-oriented approach where end users’ concerns serve
as the starting point for the process to engineer appropriate solutions to trust related issues for an e-service.
The trust management cycle is introduced and described in detail. We use an online application for reporting
gas prices as validation of the proposed cycle.
The dynamic human assessment of trust has been
identified as a major concern for user acceptance and
hence for deployment of efficient and successful on-
line applications. Not only do we need to ensure trust,
we need to create an environment and online sup-
port between end-users and e-service providers and
other actors. This means to both engender, and pro-
vide means for a positive trusting experience. Many
applications available online presuppose a high level
of trust, and thus low levels of perceived concerns or
risk taking by the user in order for users to utilize
the provided service. Examples today include online-
banking where sensitive financial information is ex-
changed between the bank and the bank customer on
a public network (i.e. the Internet) or e-health appli-
cations where sensitive personal information might be
sent over the public Internet infrastructure. It is in-
teresting to note that use of online banking, when it
was introduced in a larger scale a decade ago, indeed
was regarded with scepticism by a substantial num-
ber of new users, but is today generally accepted as
a trusted service. This example illustrates that trust
in e-services is in fact dynamic in nature, depending
on, as we will discuss later, time and context depen-
dent variances in concerns and familiarity. In this
paper we will address a principled way towards de-
sign, implementation, and maintenance of trustwor-
thy e-services. To that end we will, in the next Sec-
tion 2 Background, introduce a structured approach of
addressing trust concerns of users and transforming
those concerns into engineering principles of trust-
worthy systems. In Section 3, we will introduce a
trust management model geared at maintaining trust-
worthiness. In section 4, Validation, we analyse ex-
periences gained from a field experiment where the
e-service provided is ”Cheapest gas in the neighbor-
. In Section 5, Trust and trustworthiness, we
summarize the main aspects on those topics. There-
after, in section 6 Related work, we outline some
other contemporary approaches towards trust and e-
services. In section 7 Conclusions and future work
we present our findings and point at future work. The
final section is the Reference section.
With a multitude of novel and existing e-services on-
line questions and concerns regarding trust and credi-
bility are of major concerns by stakeholders. In the
”early” days of e-commerce concerns about online
payments was frequently discussed as a main barrier
for successful online businesses (Nissenbaum, 2000).
Today general concerns about online payments are
A Swedish web site:
Rindebäck C. and Gustavsson R. (2006).
In Proceedings of WEBIST 2006 - Second International Conference on Web Information Systems and Technologies - Society, e-Business and
e-Government / e-Learning, pages 100-105
DOI: 10.5220/0001256001000105
less prevalent and it is likely that issues related to this
has been more grounded in general payment struc-
tures in our society, that is users won’t generally have
the same doubts with respect to online payments due
to enforced and developed practices in the credit card
payment industry.
Privacy- and credibility concerns and qualities re-
lated to accuracy of information published on the In-
ternet are other factors often mentioned in trust stud-
ies and literature. We will likely discover new con-
cerns requiring attention in the future both in exist-
ing and new e-services. We claim in the paper ”Why
trust is Hard” (Rindeback and Gustavsson, 2005) that
trust in artifacts is in fact an assessment by a user if a
product or service is trustworthy. Building trustwor-
thy systems is furthermore an engineering task based
on a basis of observations about what is perceived to
be trusting qualities. To support that task we have
introduced a model that takes user related trust con-
cerns and translate those into a set of trust aspects
(e.g., my credit card number, or my identity can be
stolen). For a given trust aspect there are usually sev-
eral trust mechanisms that could be implemented to
carter for the aspects (e.g., encryption of data or ac-
cess control). Those mechanisms typically are invis-
ible or difficult to assess by a common user. To that
end, the service provider has to provide the service
or product with signs (brand names, test results, and
so on) to help the user to assess if the service meet
her concerns in a way that ensure that the product is
trustworthy. Trustworthiness, however, is a dynamic
and context dependent concept since the perception
of signs and the required mechanisms changes over
time. In order to maintain trustworthiness we propose
a trust management cycle (see fig. 1(b)). We will val-
idate our model by applying it on the ”Cheapest gas
in the neighborhood!” scenario example. As e-service
designers we can attempt to find a balanced solution
from a trust perspective that addresses the involved
actors’ different perspectives and trust concerns and
turn them into appropriate mechanisms. Ideally the
mechanisms should provide actors and end users with
signs for trust assessment purposes. The relationships
between these concepts are presented in fig.1(a)
In this section we will take a closer look at how our
suggested approach can be broken down in a number
of steps. In fig. 1(b) we introduce the trust manage-
ment cycle, a model we propose to be used in order to
develop sustainable trustworthy e-services.
Step one: From Concerns to Aspects.The first step of
the trust management cycle is the initial component
of our model. The dynamic nature of both concerns
and perception of signs are forcing us to reflect and
constantly re-assess our efforts to comply with the e-
service users’ concerns. We need to ensure that the
identified trust issues are addressed. In fig. 1(c) we
illustrate the dynamics of trust concerns.
The gap between the upper and lower dotted curve
illustrates the current set of addressed trust concerns
of an e-service at a particular point in time. The filled
curves illustrate the set of actual trust concerns at a
point in time. With actual concerns we mean the set
of the actors’ and end-users’ concerns with respect to
a particular e-service at a particular time. We can il-
lustrate points before T (e.g. P) and points in time
after T (e.g. F). At time T in fig. 1(c) we can see
that there is a mismatch between the current actual
trust concerns and the addressed ones that may cause
an insufficient treatment of relevant concerns for trust
assessment purposes. There are other notable areas in
fig. 1(c) of interest; at the time interval P we see an il-
lustration of what we ideally want to achieve, namely
a match between the actual concerns that needs atten-
tion and the identified concerns. Under such circum-
stances we are addressing all relevant trust concerns
for the current context with respect to the e-service.
At the point F we are addressing too many concerns
that are outside the scoop of the actual concern do-
main at the time of investigation. This means that we
may address issues that aren’t actually perceived as
a concern from the perspective of the involved actors
and end-users. This can in turn lead to new concerns,
e.g. if privacy is addressed in a context where it isn’t
perceived as motivated it may trigger trust concerns.
Many concerns are similar and can be condensed into
more general classifications. For instance if we have
discovered many concerns related to the privacy of
personal information this can be derived into the as-
pect privacy. We summarize this first step as: ”What
trust concerns and aspects are we addressing?”.
Step two: from aspects to mechanisms. We can’t
deploy an aspect or trust concern directly into an
e-service application or it’s context. We need to
make a transition between the identified concerns
and aspects into deployable solutions. This process
include efforts to discover, engineer and develop
appropriate trust mechanisms. A trust mechanism
is a deployable solution that encompasses one or
more trust aspects. There is no one-to-one matching
between a trust aspect and a trust mechanism; instead
we may need multiple mechanisms to meet the
concerns addressed. Consider for instance the case
where the trust aspect privacy needs attention. First
we may need to deploy a privacy policy but this may
not be sufficient; we may also need to deploy and
join a certification program such as truste in order to
satisfy users’ concerns for trust cues. A mechanism
can also be used to satisfy multiple aspects. Such an
Trust Concerns
Trust aspects
Trust mechanisms
Trust signs
Assessed trust
Context including actors, artifacts, e-services and work-
(a) Important trust concepts
1. What trust
concerns and
aspects are we
2. What trust
should be
4. Do we need
to redesign or
implement new
3. Do actors see
signs of trust-
(b) Trust management cycle
(c) The dynamics of trust concerns
Figure 1: The trust management cycle and the dynamics of trust concerns illustrated.
example includes the mechanism ”data encryption”
which can be used to satisfy both security- and
privacy aspects. The transition from concerns and
aspects into the mechanism level is an important step
since it is here decided what we will implement into
the e-service with respect to trust. The mechanisms
can be implemented in more than just one way. A
privacy policy can, be a couple of rows long or
span over several web pages. Thus each mechanism
implementations may contribute uniquely to the
addressed concerns and aspects. We conclude this
step as ”What trust mechanisms should be designed
to present signs related to the trust concerns and
Step three: From mechanisms to signs. With deployed
and implemented trust mechanisms in place the ques-
tion is if our efforts are perceived by the actors and
end-users for the cause of trust assessment. We can
through our implemented solutions suggest that we
are trustworthy and taking care of the concerns the
end-users or actors may have. However trust and
what the observers see is subjective; we can’t enforce
trust or the wished behavior onto the e-service end-
users. We need to use measures to find out how and in
what way our efforts are perceived by actors and end-
users. Finding appropriate variables and measures is
challenging and can be done by various means. Our
trust management cycle in no way limits the approach
to determine how the efforts made to encompass the
identified trust concerns are made; however our ap-
proach is based on theories of signs, a concept used
by (Bacharach and Gambetta, 2001) in the context of
trust to illustrate the point that trust as such isn’t a
directly observable property, but rather we see signs
suggesting trustworthiness such as ”an honest look”
or affiliation. These signs are derived from the vari-
ous observable properties in place (an honest person
is a subjective observation based on e.g. the look of
that person). Likewise a person may comment that
somebody looks dishonest or unprofessional through
his or her way of dressing. The concept of signs in
our context is linked to the deployed mechanisms im-
plemented. Will there be signs pointing in the direc-
tion that the e-service provider seems to be ”honest”
(a trust aspect we strive to encompass through mech-
anisms) or are signs and thus sources to assess the
trustworthiness lacking? If we find a mapping be-
tween the identified concerns and the signs presented
this is a step into a better-engineered e-service from
the perspective of trust. The third step of the trust
management cycle can be concluded as: ”Do actors
and end-users see signs of trustworthiness that covers
the identified concerns?”
Step four: Assessment. In the previous stage we dis-
cussed the relationship between signs, mechanisms
and concerns. The re-assessment phase is the stage
where we closer reflect upon the e-service context and
the concerns we need to address in our solution. In
fig.1(c) we illustrate the dynamics of concerns and
we may need to reconsider from time to time which
concerns we need to address in our solution. For in-
stance at one point in time privacy may not be an
issue but because of changes in attitudes in society
and technical advancements these issues can become
more important at certain points in time. This en-
forces us to assess trust issues during the life span of
an e-service with arbitrary intervals. We also need to
reflect upon the validity of the deployed trust mecha-
nisms; are they still up to date or do they need fine-
tuning? Should a particular mechanism be removed?
If trust concerns are still in place we may need to in-
troduce new mechanisms or re-design present ones
for that partciular concern. In some cases e.g. aware-
ness of legal changes or if a particular encryption cho-
sen is hacked we may need to completely replace a
mechanism. This step can be summarized as: ”Do
we need to redesign or implement new mechanisms
or address new concerns?”.
Step Five: Gateway to the next cycle. The concerns
gathered and findings pointing us towards assump-
tions that the trust concerns aren’t properly addressed
trigger a new round in the model. Reasons for this
could be required changes of mechanisms or the intro-
duction of new ones for a particular set of concerns.
We also must consider if the concerns we are address-
ing are the right ones at this point in time.
Our ”Cheapest gas in the neighborhood!” service will
be used to illustrate how the trust management cy-
cle can be used to reason about trustworthy e-service
development. When the service was introduced the
prices of gas in Sweden were varying almost daily due
to the volatile global oil prices. Also there were local
price wars where the price levels between different
gas stations, could vary up to as much as 25% be-
tween closely located stations. Therefore people con-
sult the service from time to time to find information
about potential bargains on gas. If a price is lower in
one station some may consider reschedule their route
and in some cases even their destinations in order to
save some money. The e-service relies on price re-
ports submitted by it’s visitors who report prices by
filling out a form.
Table 1: Condensation of mechanisms and assessments
from our scenario.
Concern: Price and information accuracy
Cycle: Mechanism: Assessment of reactions:
Date policy Ok but still comments
published on site. where visitors want
Dates when the more information.
prices where
reported added.
Forum and e-mail A way to give feedback
for feedback was about site features.
deployed to
enable comm-
Limits for false Invisible feature as long
pricing was as a user don’t attempt
introduced. to insert an
high or low price.
Registration Ok, but concerns raised
requirements regarding privacy.
Registration re- The function opened up
quirement became for anonymous
optional. Manual submissions.
approval of ano- Affected the will-
nymous reports. ingess to report prices
When the service was first deployed only one con-
cern had been identified on behalf of the end-users;
the information about the prices needed to be correct
and up to date. To avoid too old price quotes to be
published a date limit mechanism was deployed. It
was thought that this effort would mediate the correct
signs for information accuracy. This concern seemed
to be met during the initial stage of the e-service af-
ter deployment, but after a while it seemed like new
mechanisms was needed in order to assure that the
concern could be met. During the first assessment cy-
cle it turned out that users again were concerned about
the accuracy the published prices. E-mails and on-
line forum discussions revealed problems with false
reports. The initial idea was that users would be able
to spontaneously report price quotes without the need
to provide an identity. By filling out a form on a web
page the price report was published on the web site.
After misuse, which affected end-users credibility in
the e-service, mechanisms needed to be deployed in
order to sustain the trustworthiness. The problem was
addressed by forcing users to register in order to re-
port prices by stating name and email. However, it
turned out that some users where reluctant to sign up
due to privacy concerns. For this reason the registra-
tion solution became optional with manual reviews of
anonymous price quotes. Up until today this solution
has proved to function well. In table 1 we illustrate
findings from four cycles of the trust management cy-
Trust can be defined in many ways depending on
the context and circumstances, there simply is no
commonly agreed upon definition stating what trust
actually is. Trust is often seen as a mechanism used
to reduce complexity in situations of uncertainty
(Luhmann, 1988). If an online service is perceived
as to be trusted this may increase the likelihood
that the service is used by the truster although this
is no guarantee. Trust is by no means static, we
may have trust in e.g. a neighbor but due to some
event that ends with disappointments about their
behavior, or solely a suspicion about a behavior,
may cause the trust to decrease. The very opposite
may also be true since trust can grow depending on
signs suggesting somebody is to be trusted. We have
identified the following trust dimensions (Rindeback
and Gustavsson, 2005):
Trust in Professional Competence - When a decision
to delegate a task to another actor is taken this is often
based on a perception of that actor’s professional
competence. This refers to expectations about the
professional abilities (Barber, 1983) of e.g. a doctor
or banker and suggests further refinements of trust
Trust in Ethical/moral Behavior - Trust isn’t only
related to professionalism in dealing with tasks as
such, it is also suggested to be linked to values
and less tangible nuances such as ethical and moral
premises. If a trusted professional acts in a manner
that is perceived as being against common ethical
and moral norms we can choose to distrust this
person in a given context despite his professional
skills. Examples include certain types of medical
experiments or other acts that can be regarded as
unethical or even criminal if detected. Trust in
moral or ethical behavior is, of course, very context
dependent. Moral and ethical trust is discussed both
in (Barber, 1983) and (Baier, 1986).
Trust in Action Fulfillment - In cooperation a specific
trust dimension surfaces in most contexts. That is,
can a subject trust that an object will indeed fulfill a
promise or obligation to do a specified action? When
ordering a product online concerns may for instance
be raised if it will be delivered or not.
Functionality - The functionality of an artifact is
an important and natural quality of trust, e.g., the
tools are expected to function as they should. An
implicit trust condition is that an artifact or tool is not
behaving in an unexpected or undesired way by its
design (Muir, 1994).
Reliability - The reliability of an artifact is another
important criteria of trust in classical artifacts.
The tools should be resistant to tear and wear in a
reasonable way and the e.g. a VCR should function
flawless for some years. Reliability thus means that
an artifact can be expected to function according
to the presented functionality and is working when
These dimensions of trust are related to one or more
objects, in which a truster place his or her trust
(Rindeback and Gustavsson, 2005):
Trust in social/natural order and confidence - Our so-
ciety rests on basic assumptions about what will and
will not happen in most situations. For instance we
have trust in the natural order, that the heaven won’t
fall down or that the natural laws will cease to be true.
There is also a general trust related to the social order
in most of our societies, that is that the governmen-
tal representatives will do the best for the citizens and
countries they represent and follow laws and norms
as well as follow established practices accordingly.
This mutual trust isn’t something that actors in gen-
eral reflect consciously about. The non-reflective trust
serves as a basic trust/confidence level for our daily
actions where in general there aren’t any alternatives
to the anticipated risks. The notion confidence (Luh-
mann, 1988) is sometimes used in situations where
actors in reality have no choice. It isn’t a viable op-
tion to stay in bed all day due to concerns about the
social or natural order.
Trust in communities - Humans are often part of a
larger community. In the society we have companies,
non-profit organizations, governmental institutions
and other groups of humans, which often act ac-
cording to policies, and interests of the community.
In many cases the trust may be attributed primarily
(or at least in part) in the behavior in a community
e.g. a hospital. On the other hand, a hospital may
be perceived as trustworthier than another due to
better reputation regarding the perceived treatment
and quality of their staff. Depending on the context,
trust by a subject may be placed on the object
being a community, an individual representing the
community, or both.
Trust in humans - In many situations we attribute
trust towards other humans, we may trust a particular
person about his capabilities or trust his intentions
about a particular action. When buying a used car
for instance we may trust a car salesman to a certain
degree or trust a neighbor being an honest person.
Trust between humans has been studied among others
by (Deutsch, 1973; Gambetta, 1988; Rempel et al.,
Trust in artifacts - Trust in human-made objects such
as cars or VCR:s are in some cases discussed in a
manner which implies that these objects can be seen
as objects in which trust is placed. For instance ’I
trust my car and VCR’. This means that our expecta-
tions regarding the objects with respect to reliability
are in some sense confused with or attributed for trust
in humans enabling the intended behavior.
The distinction between what or whom we trust is im-
portant when determining how to address trust issues
in a given context. E.g. if a patient don’t trust a doctor
this may have different causes which can be related to
the person as such (a human) and his or her profes-
sional competence, artifacts or maybe the reasons are
that the hospital as such isn’t to be trusted, the doctor
is just the representative towards the lack of trust is
attributed. When developing e-services we also must
consider the cause of particular trust concerns. Are
for instance the concerns technology-oriented or are
there other reasons for the identified trust concerns?
Trust and trustworthiness shouldn’t be confused.
An online vendor or a person can suggest that they
are trustworthy by their actions or through e.g. a web
site (Sisson, 2000). But it is up to the truster to assess
these suggestions.
Two strands of dealing with the problem of trust have
been identified. In some work and traditions there
is an implied idea that we can solve the problems
related to trust by encryption and security solutions
(Nissenbaum, 2000). Others suggest the need to cre-
ate an atmosphere of trust and understand issues re-
lated to different situations and actors. One approach
that deals with trust in risky environments such as
e-commerce is the model of trust in electronic com-
merce (MoTech) (Egger, 2003). It aims to explain
the factors that affect a person’s judgment of an e-
commerce site’s trustworthiness. MoTech contains of
a number of dimensions intended to reflect the stages
visitors goes through when exploring an e-commerce
website. The dimensions pre-interactional filter, in-
terface properties, informational content and relation-
ship management will be described below. Each of
these components addresses factors that have been ob-
served to affect consumers’ judgment of an on-line
vendor’s trustworthiness. Pre-interactional filters re-
fer to factors that can affect people’s perceptions be-
fore an e-commerce system has been accessed for the
first time. The factors presented are related to user
psychology and pre-purchase knowledge. The first
group refers to factors such as propensity to trust and
trust towards IT in general and the Internet. Pre-
purchase knowledge is related to Reputation of the
industry, company and Transference (off-line and on-
line). The second dimension of MoTech is concerned
with interface properties that affect the perception of
a website. Here the components are branding and us-
ability. Factors in the branding component are ap-
peal and professionalism. The usability component
factors are organization of content, navigation, rele-
vance and reliability. The next dimension, informa-
tional content contains components related to compe-
tence of the company and the products and services
offered and issues regarding security and privacy. The
fourth and last dimension reflects the facilitating ef-
fect of relevant and personalized vendor-buyer rela-
tionship. The components Pre-purchase Interactions
and Post-purchase interactions are related to factors
such as responsiveness, quality of help and fulfilment.
This model is interesting and divides the relationship
between the vendor and user into units that can be
analysed further.
We introduced the trust management cycle, a princi-
pled approach to address the problem of trust in online
e-services in a structured manner which takes a start-
ing point in actual trust concerns expressed or identi-
fied in the user community. These concerns need to
be turned into deployable solutions by means of trust
mechanisms. We also presented validation of the cy-
cle by applying it on the ”cheapest gas in the neigh-
borhood!” scenario. We need to further validate the
model and investigate constituents of e-service con-
texts in order to find better ways to deal with trust
issues. We also see a need to understand the relation-
ship between specific signs and mechanisms in order
to better understand the characteristics of good trust
mechanisms. This will hopefully give us better tools
to deploy and design trustworthy e-services.
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