Information from the physical world is increasingly being digitalized and shared in social networks. We share our locations, tag photos and add different kinds of informal awareness cues about the physical world to our online communities. In this paper, we investigate the privacy implications of shared context cues in social networking services. We present an experimental mobile application, which allows users to add different descriptions of context information to their Facebook and Twitter status updates. The application was used by 12 persons during a two-week user trial using their own devices and Facebook accounts. The results indicate that user-defined abstractions of context items were often preferred over more accurate indicators due to privacy concerns or discomfort in sharing. We also found out that using shared context from friends in vicinity needs careful design to overcome the extended privacy implications.

1. Understanding the Privacy Implications of Using Context-based Awareness Cues in
Social Networks
Ville Antila Jussi Polet
Context-Awareness and Service Interaction Context-Awareness and Service Interaction
VTT Technical Research Centre of Finland VTT Technical Research Centre of Finland
Oulu, Finland Oulu, Finland
ville.antila@vtt.fi jussi.polet@vtt.fi
Abstract — Information from the physical world is increasingly the user, the currently active applications in the mobile
being digitalized and shared in social networks. We share our device, information about the current device, information
locations, tag photos and add different kinds of informal about the friends around, the current location as well as
awareness cues about the physical world to our online information about the surroundings. We deliberately selected
communities. In this paper, we investigate the privacy a wide variety of context types (even some more
implications of shared context cues in social networking unconventional ones) to get better understanding over which
services. We present an experimental mobile application, types of information are considered useful and which are
which allows users to add different descriptions of context more privacy sensitive than others. Through a two-week user
information to their Facebook and Twitter status updates. The
trial we explored the usage and privacy implications of
application was used by 12 persons during a two-week user
different abstraction levels when publicly sharing contextual
trial using their own devices and Facebook accounts. The
results indicate that user-defined abstractions of context items information. The goal was to shed light into the practical use
were often preferred over more accurate indicators due to of context information in informal information sharing and
privacy concerns or discomfort in sharing. We also found out the implications that these practices have in designing
that using shared context from friends in vicinity needs careful context-aware applications, especially regarding the
design to overcome the extended privacy implications. perceived privacy effects.
Keywords - Awareness Cues; Context-awareness; Mobile II. RELATED WORK
Applications; Privacy; Sensing; Social Networks; Through the analysis of contextual information derived
from mobile device usage patterns it is possible to infer a lot
I. INTRODUCTION of potentially privacy-sensitive information. Eagle and
Pentland demonstrate the ability to use mobile devices to
Social networks are increasingly used to share digital
recognize social patterns, infer relationships, identify socially
artefacts, which are often “tagged” with contextual
significant locations, and model organizational rhythms [4].
information from the situation or event, mirroring its
These life patterns can be used as input for creating narrative
physical counterpart. Photos can be tagged with GPS
events [17]. In the work of Miluzzo et al. they propose a
coordinates, or presence information can be shared by an
system, which is capable of sensing various activities
instant messaging application. Furthermore, location check-
(location, physical activity, social and physical surroundings)
ins, adding sports activities and giving informal awareness
and share this information on various social networking
cues in status updates are increasingly used functionalities in
platforms [12, 13]. Moreover, the use of mobile devices to
SNSs (Social Networking Services), such as the Facebook.
create context-aware content to social networking services
In many cases the shared information is tailored to a specific
has grown recently. Services such as Foursquare, and
case, containing detailed information like GPS coordinates
Facebook Places can be used to check-in to venues using
with textual descriptions, which can render the information
mobile devices equipped with GPS-chips. In [21] context
too specific or too ambiguous to fit different use cases. Often
information, such as location, proximity of friends and
the level of information disclosure can be also hard to
motion, is used to create suggestion and validation of check-
manage for the user. We claim that in order to ensure the
ins into these kinds of applications. Furthermore, location-
privacy and user control there should be means for
based formation of social networks has been researched
abstracting this information regarding the specific needs and
recently [10]. As the social computing is getting more
desires of the user.
mobile and pervasive there has been an increase in interest of
In this paper, we investigate the practices of abstracting
exploring the social-side of context-awareness [5]. In
contextual information for public (or semi-public) sharing.
addition to mere location or physical activity of the user, the
To facilitate this, we have developed an experimental mobile
systems could benefit from the knowledge of the social
application, which allows users to add different types of
surroundings. For example, there has been research to
contextual information to their Facebook status updates in a
explore the social use of ubiquitous computing in urban areas
format of a story. The types of contextual information
[7]. In this paper, we suggest mechanisms to gather context
explored in this study include the current physical activity of
from the surroundings to enhance both availability and

2. relevance of context information (e.g. querying the devices Our hypothesis is that in many cases, rather than using exact
around). In addition, we investigate the extended privacy parameters provided by context recognition modules for
implications of such sharing mechanisms from the user’s describing the situation, people would like to add semantic
point-of-view and point out design challenges based on the meaning by using more abstract notions. As Benford et al.
findings. argue: “[in this context,] declaring one’s position is perhaps
as much about deixis (pointing at and referencing features of
III. PRIVACY IMPLICATIONS OF CONTEXT-AWARENESS IN the environment) as it is about telling someone exactly where
SOCIAL APPLICATIONS you are” [2]. In addition Tang et al. argue that social-driven
The perceived privacy implications of shared presence location sharing favours semantic labels and information
information are largely related to the information type as blurring, but also use location sharing as a way to boost self-
well as the intended audience, but people are also willing to presentation [19].
stretch the boundaries of privacy in exchange for useful In this work, we explore not only the different
services [9]. Privacy is a dynamic and continuously abstractions of location information, but also other
negotiated process [16]; in practice people tend to commonly available and used context information types. We
appropriate the usage of a service for their own needs [1]. selected six basic information types that the users could use
From the technical point-of-view there are two distinct to describe their context. The selected context types are
approaches. First, there has been research on developing activity, applications, device, friends, location and
frameworks to help the development of privacy-aware surroundings. These context types are described more in the
participatory sensing applications. For example in [3] the next sections. Furthermore, we were interested in the
privacy implications of sharing the sensory data of one’s perceived privacy of different levels of abstraction of
mobile device are discussed and a framework is presented. contextual information.
Similarly, in [8] a privacy-aware framework is proposed, The narrative status update message is generated from
which enables the sharing of contextual data between users the freeform user-inputted status message and the context
and central servers while at the same time maintaining the information gathered by the mobile application and selected
security and privacy of each user. Furthermore, there has by the user. The rule for generating the message is as
been some recent research on enabling the knowledge of the follows:
situation and its privacy implications to automatize certain
functionalities. For example, in [6] contextual data is used to “[User-defined message]
determine the mobile device locking timeout and unlocking Sent from [Location] using [Device] with [Friends]
method dynamically, depending on the perceived safety of
nearby, while [Activity] and [Applications
the current context (home, office etc.).
On the other hand, in many application cases the notion Activity] in [Surroundings].”
of context itself is very dynamic and ever-changing. Mancini
et al. argue that context is not objectively defined by settings, As an example, a status update message generated with
actions or actors themselves but by the meaning that they the previous rule could be (not all context fields selected):
acquire at any given time from the subjective perspective
[11]. Furthermore the privacy preferences themselves also “Thinking of mesh-networks!
change in time and are dynamic in different situations.
Awareness of consequences of contextual information Sent from Lugano, Switzerland with 2 Facebook friends
sharing is said to be important factor for the users to get a nearby, while walking and using Maps.”
better grasp on how their actions affect the level of
V. PROTOTYPE APPLICATION
information disclosure [18, 20]. One of our leading design
goals in this work has been to explore the practical usage of The prototype application consists of a mobile client and
different levels of abstractions by giving the user full control a server-side application, which is integrated with Facebook
over the level of information they share. and Twitter. The overall prototype architecture is depicted in
the Figure 1.
IV. CONTEXT-BASED AWARENESS CUES The mobile application gathers context data from the
Oulasvirta et al. have studied how sharing context device itself, available sensors and by using Bluetooth to
information could create awareness about the user’s situation collect data from nearby devices. The application presents
and thus enhance communication and collaboration [14]. the sensed context information to the user along with
They also discuss the different design requirements for proposals for other semantic abstractions, which have been
representing context-based awareness cues [15]. used to describe similar contexts earlier. User can also define
To explore the usage of shared context cues, we a new context element which will be then coupled with the
developed an application which allows people to include raw context data gathered from that situation (enabling the
contextual information to their status updates they send to application to suggest it later on). After selecting the context
Facebook. In addition to the selection of different context items and their abstractions, the status update is sent to the
types, the user can also decide the desired abstraction level server. The server application stores the received context
(e.g. coordinates, address or semantic label such as “office”). data into a semantic model (including the raw data from the
sensors and the associated abstraction) and creates a context-

3. enhanced status update, which is used to create a new status A. Context Recognition
update in Facebook (Figure 2). The context recognition is based on different “sensors”
on the mobile device, such as the accelerometer, ambient
light detector and GPS data, the open applications on the
Social Media mobile device, the device system information, the nearby
Bluetooth devices and the WLAN access points. Based on
ContextCapture this data, context descriptions and suggestions are shown to
Server the user. For example, based on the ambient light detector
data, information about the current lighting is shown to user,
such as “Dark lighting” or based on the GPS data, the
Web
current street address, GPS coordinates and current
temperature and weather descriptions are shown. In the list
below we describe all the context information items
Network supported by the application:
User connection
with (3G/WLAN)
Mobile
Phone Other user • Activity – Based on the accelerometer data, a decision is
with mobile made whether the user is running, walking or still by
phone
using movement detection algorithms. This is then
Bluetooth shown to the user as a description of the current physical
connection
activity abstraction.
• Applications – Based on the data gathered from the
mobile device, the currently open applications are
shown to the user as a description of the current virtual
activity abstraction.
• Device – Some of the data gathered about the mobile
device itself, such as the device type, is shown to the
user.
• Friends – Based on the Bluetooth device and service
scan data, the current nearby Bluetooth devices and
ContextCapture friends are shown to the user as the
current social context. The current ContextCapture
friends’ detection is based on the Facebook friends and
ContextCapture use, i.e. if the users are friends in the
Facebook and both are using ContextCapture and are
nearby, they are shown in the current social context
abstractions.
• Location – Based on the GPS, network and WLAN scan
data, the current street address, GPS coordinates,
network cell ID and nearby WLAN access points are
shown as the possible current location abstractions.
• Surroundings – Based on the ambient light detector and
Figure 1. Left-Up: The prototype architecture. Right and GPS data, the current ambient lighting and the
Bottom: The ContextCapture mobile application UI. temperature and weather (which are downloaded based
on the GPS coordinates) are shown as the current
physical surroundings abstractions.
B. Protocol for Exchanging Collective Context
The client-to-client communication is done over a
Bluetooth connection, using a specified communication
protocol. The mobile client notices whether there are other
devices nearby offering the specified service. If so, the
devices exchange MD5-hashed IDs, which are coupled with
the Facebook accounts. If the mobile client is lacking some
context information, for example the GPS coordinates; it will
request that information from the nearby friends, which will
reply with the data, should they possess it. The syntax for the
exchange protocol is as follows:
Figure 2. Example of using context-based awareness cues in a
status update shown on Facebook

4. CCRAControlProtocol:<role_name>:<BT_name>: VI. USER STUDY
<command>:<parameters>
To evaluate the ContextCapture application and to find
answers to our research questions, we arranged a trial, where
For example, the mobile client requesting for weather 12 participants used ContextCapture for two weeks with
data from a nearby ContextCapture friend takes the client their own mobile phones in their everyday lives. This section
role and sends a request as follows: introduces the user study and the results from the trial.
A. User study design
CCRAControlProtocol:Client:ClientBluetooth
Name:WTHR:Request The aim of the evaluation was to study how people
would use context information in their status updates and
what kind of abstraction levels would be suitable for
And the service running on the specified device replies:
presenting the context information regarding the perceived
privacy effects. To discover these matters, two distinct
CCRAControlProtocol:Server:ServerBluetooth research questions were set:
Name:WTHR:-3 degrees Celsius,Sunny
1. How do users perceive privacy implications of
The ContextCapture Facebook application is located at shared context cues in social settings (such as status
the server and relays the incoming status update messages updates)?
from the mobile client to the Facebook. The client-to-server 2. How do users perceive the privacy implications of
communication is based on normal HTTP GET and POST collaborative context gathered from the
operations, where the data sent is JSON formatted. The two surroundings (such as identifying friends in their
main communication sequences between the mobile client status updates)?
and the server are the login and status update.
In the login sequence, the mobile client sends the login As we wanted to ensure that all significant data would be
key, which the user has got from the ContextCapture collected, various data collection methods were used. In the
Facebook application and the MD5-hashed IMSI string. This beginning of the trial we had an initial web questionnaire,
way, the user’s Facebook account and the user’s mobile which included questions about the Facebook usage and
device are coupled together at the server by using the expectations towards the ContextCapture application. During
Facebook user ID, ContextCapture login key and the MD5- the trial, participants could report about their experiences
hashed IMSI string. with the application through a web-based diary
In the status update sequence, the mobile client sends a questionnaire. The diary inquired, which of the context types
JSON formatted data package containing all the context data had been most useful to the participants and whether they
and the user-given abstractions to server. The server then had got any comments and feedback from their Facebook
parses the message and creates a story-like status update friends related to the contextual status updates. It also
string, which is sent as a wall post to Facebook. Depending included questions about the experiences related to privacy.
on the success, the server sends back a reply, which also The participants could also give general free-formatted
contains the current ContextCapture friends so that the feedback about the study through the diary questionnaire. At
mobile client can update the friends list if there have been the end of the trial all participants were interviewed for
changes. getting more in-depth information about the user experience.
Interviews also included a background information sheet,
C. Used Technologies
which was given on paper. It contained demographical and
The mobile application was implemented for Symbian closed scale questions, which were easier to ask in written
and Android devices. Qt was used in the Symbian form.
application and the persistent storage for context data was
implemented with the Qt APIs for SQLite. The server-side B. Participants
implementation was developed using J2EE web framework. The first criterion for the trial participants was the fact
The contextual data is saved using RDF format with Jena that they had to be active Facebook users. Some of the
Semantic Web Toolkit and persisted in a PostgreSQL participants had to be connected through Facebook, as we
database. The context information was chosen to be persisted wanted to have groups of people, who could see each other’s
in the server-side for two reasons, one reason was that we status updates and be able to use friends related context
wanted to control the user study results, and the other reason information via “Facebook friends nearby” –functionality. In
was to use the gathered context information as the basis of addition, the participants had to have suitable mobile phones
collective intelligence, enabling recommendation and supported by the application. Due to this, we decided to
adaptive filtering content based on the context in later stages invite only VTT 1 and NRC (Nokia Research Centre) 2
of the research. The SNS integration was implemented using employees to the user study.
the Facebook and Twitter APIs, which enables
functionalities such as the user authentication and status 1
http://www.vtt.fi/?lang=en
updating.
2
http://research.nokia.com/

5. Total of 12 users participated in the trial, six male and six Sharing friend’s location was also one thing, which
female. The age of the participants was between 30-46 years, invoked thoughts. In many participants’ opinion sharing this
37.25 years on average. Participants used ContextCapture kind of information without permission is not acceptable. So
with their own mobile devices and personal Facebook there should be some way for asking a permission to share
accounts during the trial. All participants were experienced context data including other users. Friends’ names were also
Facebook users as 25% of them had used the service 1-2 often viewed as private information and participants
years and the rest for over two years. Figure 3 shows how preferred to use more abstract words, like “group of
often the participants were used to send status updates before friends”, instead of giving the exact names.
the study. One of the key findings was the fact that participants
were clearly interested in context data and in using a context-
aware application. Context information was seen as highly
interesting, but the participants hoped that they could have
had even more control in the level of abstraction. In addition,
more abstract names like “home”, “work”, “kindergarten”
were seen as more useful and secure in many situations than
the exact street addresses. There were interest towards
getting more specific location information, bare street
addresses were seen as not useful, but the application should
recognize the place, which is located in the address, like a
movie theatre or a shop.
E. Implications for design of context-aware social
Figure 3. Frequency of sending status updates (generally and applications
via mobile phone). Based on the findings we can summarize the implications
for the design of context-aware social applications,
C. Trial setup especially when dealing with privacy sensitive information,
First we sent email instructions to the participants on how as following:
to download and install the application. The email included a
short description of the study and its purpose, a short manual, 1. With applications dealing with privacy sensitive
the link and instructions on how to install the application and information, the information disclosure and privacy
a link to the initial web questionnaire. The users were should be fully controlled by the user
requested to fill in the initial questionnaire after they had 2. By giving the freedom for users to control the disclosure
successfully completed the installation of the application. and abstraction level of contextual information, we
This indicated that they had started the trial. argue that it creates:
The participants used the application for approximately
two weeks. During that time, they could tell their • Meaningfulness and motivation for the users,
experiences through the web diary. We asked them to fill in • And in the same time allows the system to
the diary at least five times and preferably in separate days. gather a set of user-defined context labels with
Total of 26 diary entries were made during the trial. At the different abstraction levels (which can be
end of the trial, we interviewed all the participants; nine of associated with the gathered low-level sensor
them with face-to-face interviews and three of them via data).
telephone interviews. Interviews were semi-structured,
including questions dealing with users’ expectations, The lessons learned from developing the application and
attitudes, privacy and the most pleasing and unpleasing running the user study include that it is clearly important to
experiences related to usage. The interviews lasted design the application to give full control of the level of
approximately 30 minutes each. information disclosure to the user, even case-by-case
D. Findings manner. We found out that privacy is indeed a dynamic and
continuously negotiated process in which a rigorous set of
The participants were clearly aware of their privacy and prior rules can render the application useless. When put in an
had thought it while using the application. For example, the actual situation, people often appropriate the shared
participants did not use the addresses of their homes or information level according to the needs of the moment
kindergarten their children were, although the audience rather than using a non-changing privacy policy.
consisted of Facebook friends known by the participants. It
seemed that the accurate location of these places was too VII. DISCUSSION AND CONCLUSIONS
sensitive to be shared. In addition, many of the participants In this paper, we explored the usage of different types
stated that the semantic meaning of the place is enough. For and abstractions of context information in informal
example, saying that “I’m at home” is adequate enough for information sharing and the practical usage of these
the people the message is meant for, i.e. my friends know abstractions to maintain certain-level of privacy. We
where I live. approached this challenge by developing an experimental

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