Modeling NFC-triggered User Interactions with Simple Services in a
Smart Environment
Antonio P. Volpentesta and Nicola Frega
Giudalab, DIMEG, University of Calabria, Rende (CS), Italy
Keywords: NFC, NFC Interaction, Context Awareness Service, Mobiquitous Services, HCI, Smart Environment.
Abstract: NFC is an emerging wireless technology that can enable users to interact with smart objects in a smart
environment. NFC applications have been developed to provide services like ticketing, access control, tourism
information extension, voucher redemption and contactless payment. The interaction technique is a sort of
“tap-and-go” as it is currently employed in smartcard usage for travel operations and workspace
access/logging. Employing a recently introduced framework for human interaction with mobiquitous services,
we present a model of NFC-triggered user interactions with simple context-awareness services in a smart
environment. The rationale is to provide a conceptual tool for both an appropriate communication among
NFC ecosystem stakeholders and the interface design of NFC apps with a generic applicability. Lastly, we
discuss the application of the model in a project which required the design of NFC-based interactions with
services for car parking management in a city area.
1 INTRODUCTION AND
BACKGROUNDS
Near Field Communication (NFC), a two-way
communication technology based on RFID, is a
relevant enabler for smart environment applications,
where people can invoke associated services by
bringing together two NFC compatible devices close
to each other. Nowadays, NFC technology has been
employed in a large range of business/consumer
applications and services in various industry sectors.
Nevertheless, many researchers continue to propose
application scenarios or use cases in order to explore
new opportunities of NFC apps that can generate
significant business value through the provision of
more accurate and timely information, (Dodson and
Lam, 2012; Haselsteiner and Breitfuß, 2006).
However, a characterization of NFC interaction with
services is still needed in order to provide both a
common understanding of capabilities and features of
NFC apps and a support to the design, development
and deployment of novel services.
NFC-based interaction uses two NFC enabled
devices to facilitate human interaction with
information and services. Such interaction is
performed by means of a very elementary touching
technique consisting in a simple tap gesture, i.e. the
user brings a NFC device into close proximity to
another. More precisely, two compatible NFC
devices (e.g. a contactless card and a mobile phone)
communicate with each other when they are less than
few centimeters nearby; the communication may
occur either between two active devices, powered and
equipped with data processing capability, where two
NFC peers actively exchange messages, or between
an active device and a passive device that only serves
as a passive tag.
This communication provides simple and fast data
transfer including calendar synchronization or
electronic business cards, as well as access to online
digital content. Therefore, NFC technology permits
creating a bridge between digital and physical worlds
and it allows some applications in a smart
environment to be made more personalized, dynamic,
and intelligent (Chang et al., 2011).
Actually, NFC smart phones that embed the NFC
device are employed in a growing number of
applications and services (Volpentesta et al., 2013;
Beny’o, 2007). An NFC phone can switch operation
modes. Therefore, it can not only serve as the basic
key for authenticating entry to a smart environment
(e.g., a household environment), but also it can
provide personalized control of a variety of smart
objects (e.g. smart home appliances) that are driven
by the request from NFC mobile phone using
96
P. Volpentesta A. and Frega N..
Modeling NFC-triggered User Interactions with Simple Services in a Smart Environment.
DOI: 10.5220/0005377500960104
In Proceedings of the 17th International Conference on Enterprise Information Systems (ICEIS-2015), pages 96-104
ISBN: 978-989-758-098-7
Copyright
c
2015 SCITEPRESS (Science and Technology Publications, Lda.)
predefined ontology and rule based reasoning (Chang
et al., 2013).
Unlike other human-computer interaction
technologies and styles that require specialized
controllers and instructions, NFC interaction is a sort
of easy touch-driven interaction between physical and
digital space without requiring any particular training
process: a tap gesture action is translated into
information flow in digital space, which is in turn
reflected by media activity in physical space through
an associated output device resource. For instance, a
NFC enabled smartphone can be used as an active
scanner in order to detect a tag in its range, and
trigger an interaction with a service that is provided
through some output device (phone, TV, stereo,etc.)
(Chen et al., 2011). Apart from simple interactions
with single tags, NFC have been used for more
elaborate interactions with physical user interfaces
(UI) that comprise multiple tags, i.e. multi-tag
interactions, where different features of NFC
applications are mapped to multiple tags and spread
on physical UIs, in order to allow a user to select
them directly (Broll and Hausen, 2010). Application
examples are given by smart posters for mobile
ticketing (Broll et al., 2009), home care services
(Häikiö et al., 2007), sharing multimedia content
(Sánchez et al., 2008), and dynamic NFC-displays
(Broll et al., 2011).
In this paper, we focalize our attention on NFC-
based smart environments where simple context-
awareness services are provided by networked
computing devices that include NFC enabled devices
and application servers running in a separate
computer room, or remotely on a “grid”. A simple
service is intended as a service that just returns a
simple result when it is invoked by the user; its
execution delivers an expected result that fulfills
user's needs without requiring any other information
to the user.
In (Volpentesta, 2014), framework for human
interaction with mobiquitous services has been
introduced. Such framework is independent of the
particular technology employed in the smart
environment. In this paper, we focus on NFC-based
smart environments, and we use that framework in
order to provide a model of NFC-triggered user
interactions with simple NFC services. This model
could be regarded as a conceptual tool for supporting
either an appropriate communication among NFC
ecosystem stakeholders and the interface design of
NFC apps with a generic applicability. Lastly, we
discuss the application of the model in a project which
required the design of NFC-based interactions with
services for car parking management in a city area.
2 NFC-BASED SMART
ENVIRONMENT
In this paper we define a NFC-based smart
environment as a small world populated by users,
simple context-awareness NFC services, and
interaction resources (NFC enabled devices and
output devices) interconnected to some application
servers that may run in a remote place. A context-
awareness NFC service may provide a user with
access to information about the environment
surrounding him (weather conditions, up-to-date
traffic, …), organizational systems (current product
prices, local events, flight status, …) and other people
(phone numbers, birthdays, meetings, …) whom he is
interested to have relations, as well as it may allow a
user to control physical devices (printer, home
appliance, …), or to pass information assets (buying
preferences, medical data, …) to an organizational
system.
In what follows we discuss the main elements of
an NFC-based smart environment and their inter-
relationships.
2.1 Interaction Resource
In the NFC-based smart environment, we distinguish
between input and output resources, and we assume
that any input resource is associated to a simple
service and an output resource.
An input resource is constituted by two
compatible NFC enabled devices one of which may
act as a NFC reader and the other one may act as a
NFC target, i.e. a source of data. The NFC reader
(e.g. an NFC smart phone) reads data contained by
the NFC target that is a physical device with
attached/embedded an NFC tag. Moreover, the NFC
reader may have built-in pre-processing options (e.g.
filtering and reorganizing the data) and sends
processed data to the simple service application by
using other protocols (e.g., wi-fi, 3G/4G). These two
devices may trigger the simple service only when
they are brought together into close proximity, and
they are compatible with respect to the NFC reader
logic or the service application requirements (the tag
content should be in a format ready to be processed
by either the NFC reader or the simple service
application).
An output resource is either a device controlled
by a NFC reader to provide a basic feedback as
acknowledgement that the tapping action has been
successful/unsuccessful, or a device controlled by the
simple service to provide the needed response. The
service response may be provided via a video/audio/
ModelingNFC-triggeredUserInteractionswithSimpleServicesinaSmartEnvironment
97
haptic communication channel (e.g., graphic/textual
message on a screen, a sound from a speaker, a
vibration on a smart phone).
2.2 Simple NFC Service
It is a software function, together with the policies
that control its usage. It just returns (depending on
the current context situation) a simple result as it is
invoked by an input resource, i.e. a pair of compatible
NFC reader and NFC target that are tapped together;
the tapping action is performed by the user and it
triggers the service execution; the data contained in
the NFC tag, and possibly preprocessed by the NFC
reader, are used as input to the service; the execution
of the simple service delivers the expected result on
the associated output device, and we assume that it
fulfills user's needs without requiring any other
information or choice from the user.
2.3 User
A user is a person that enters the spatial environment
and is capable of:
being aware of interaction resources, their
location inside the spatial layout, and the
associated simple NFC services. Previous studies
have tackled the usability problem of identifying
the interaction resources in a NFC-based smart
environment. Such a problem arises when a user
is unfamiliar with NFC technology and adopts
“false” mental interaction models previously
developed (Mäkelä et al., 2007). In order to
overcome it, researchers in user interface visual
design have proposed user centered approaches
that make use of special symbols and a graphic
language to visualize NFC resources and the tap-
based interactions with them (Hang et al., 2010;
Arnall, 2011);
approaching interaction resources and knowing
how to initiate the interaction with them. The user
should have normal physical abilities and
sufficient experience to overcome their initial
difficulties and inhibition threshold (Hang et al.,
2010);
triggering the interaction with a simple service.
The user should be able to grasp a mobile NFC
device (e.g. a NFC smart phone or a NFC-tagged
card/wristband) and bring it to a complimentary
NFC device (NFC reader, NFC-tagged physical
object) within a short range. However, we take
into account possible problems concerning the
incorrect alignment of NFC target and NFC reader
devices as they are tapped together (Geven et al.,
2007).
Fig. 1 illustrates how interactive resources, simple
service, and user interact in a NFC-based
environment, bridging the gap between virtual and
physical spaces.
Figure 1: The NFC-based environment.
3 NFC-TRIGGERED USER
INTERACTIONS WITH
SIMPLE SERVICES
As part of the interaction model, some authors
identified the stages of a NFC-triggered user
interaction with simple services in a NFC-based smart
environment (Sanchez et al., 2011; Hang et al., 2010).
These stages may be summarized in: discovery
(exploring the environment, locating and approaching
the input resource to interact with the simple service
associated to it), match (bringing together the pair of
NFC devices of the input resource) and usage
(providing other inputs and commands required by
the service application at any step of the interaction).
We focalize our attention on the match stage, i.e.
when the user brings together two NFC devices in
order to invoke the associated simple service. We
presume that the previous discovery stage has already
been properly performed by the user (this is the case
when an appropriate physical user interface design
approach has been configured around user
requirements, or when the user has already got
accustomed to the environment). We also neglect the
subsequent usage stage, because it is not meaningful
in the interaction with simple service, as only one
service function is executed after tapping together
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two compatible NFC devices.
Beyond user, simple NFC services and interaction
resources, other basic elements of this framework are
represented by interface context, actions performed
by a user or a simple NFC service, as well as
interaction information flow associated to any pair of
user and simple NFC service. Let us specify these
elements and their inter-relationships in the case of
NFC-triggered user interaction with simple NFC
services in a NFC-based smart environment.
3.1 Interface Context
The interface context is a model for a structured
representations of entities (called items) whose
instances (called items states) describe a single
situation that may occur in any interaction between a
person (i.e., a user) and a simple NFC service. The
model consists of only those items whose current
states are needed to be known by a user and a simple
NFC service in a contextualized interaction. Interface
context items are of the following five types:
Identity. It concerns the identification of the
current user, and the input resource (a compatible
pair of NFC reader and NFC target) involved in
the interaction (a simple service is univocally
determined by an input resource);
Distance. It is a discrete measure of the relative
distance between the two NFC devices of an input
resource. Usually, it is a binary measure that
indicates whether these two devices are in range
or out of range;
Location. This refers to the location where the
paring of the two NFC devices of an input
resource occurs. It may be an absolute geo-
location (i.e. determined by GPS position of one
of the two NFC devices) or a relative to a fixed
point in the physical environment (e.g. a position
in a grid, like in mobile interaction with dynamic
NFC-displays (Broll et al., 2011)). We assume
that one of the two NFC devices has a fixed
position;
Time. It refers to time-related properties (current
date and time, elapsed time from previous
interactions, etc.) of the interaction between a user
and an input resource. The item state is
determined by an internal clock of one of the two
devices and it is expressed in an appropriate
date/time format;
Environment. It refers to physical conditions of
the output resource associated to an input resource
in the spatial environment surrounding the user.
An output resource is used as both a RF feedback-
notifier of the user tapping action and a container
of the simple service response.
Moreover, it is important to distinguish between
interface context items that are changeless or
changeful. A changeless item is an item whose state
cannot be changed by the execution of a user or
service action during an interaction, whatever its
current state and user or service action may be. Of
course, a changeless item state can be changed by an
action performed by an external entity different from
a user and a service. An interface context item is
changeful when one (or some) of its states can be
altered by a user or a service action. In an interaction,
a changeful item state can affect and be affected by
the user or service behaviour, while a changeless item
state can only affect the user or service behaviour (for
instance, its change can trigger an action). In NFC
interaction, the distance and environment items are
the only changeful items, while the others are
changeless items.
3.2 Actions
According to (Volpentesta, 2014), it is an act,
performed by the user or the service, which changes
states of some items and lets the performer
counterpart to get information about the current
interface context. Therefore, any act, performed by
the user or the simple NFC service, that does not
change the state of any item of the interface context
(and thus not communicating any information to the
counterpart) is not considered an action.
In NFC interaction, a user action is a physical act
that changes relative distance between the two NFC
devices of an input resource, thus changing the
distance item state (let us denote its values as 1 for in
range, and 0 for out of range). A simple service action
is the execution of a software function that changes
the state of a RF feedback notifier item and , possibly,
the state of the service response notifier item.
Notifications may occur through an
audio/visual/haptic a sign in the user surrounding
environment and notifier item state may be
represented by a binary variable (0 for “unnotified”
and 1 for “notified”)
Distance, RF feedback notifier, and service
response notifier are the changeful interface context
items whose states can be changed by actions
performed by a user or a NFC simple service it’s
described in what follows.
- User actions:
u1: bringing together two NFC devices of an
input resource. This action switches the
distance state from 0 to1, and it is externally
triggered by the user intent to consume the
ModelingNFC-triggeredUserInteractionswithSimpleServicesinaSmartEnvironment
99
simple NFC service associated to the input
resource;
u2: detaching two paired NFC devices of an
input resource. This action switch the distance
status from 1 to 0, and it is triggered by user
awareness of the notifier item state change
from 1 to 0.
- NFC simple service actions:
s11: sending both a confirmation that the NFC
target has been correctly read, and the service
function results to the output resource. This
action changes from 0 to 1 both the RF
feedback notifier item state and the service
response notifier item state of the output
resource. The action is triggered by the
execution of u1 when the two NFC devices are
compatible and correctly aligned;
s12: releasing the output resource. This action
changes from 1 to 0 both RF feedback notifier
item state and the service response notifier
item state of the output resource. The action is
triggered by the end of the execution of s11;
s21: sending an error message to the output
resource that the NFC target has not been
correctly read. This action changes the RF
feedback notifier item state from 0 to 1. The
action is triggered by the execution of u1 when
the two NFC devices are not compatible or not
correctly aligned;
s22: releasing the output resource. This action
changes the RF feedback notifier item state of
the output resource from 1 to 0. The action is
triggered by the end of the execution of s21.
The interaction graph is the oriented graph where the
nodes are associated with the states set of the
changeful interface context items and the arcs are
associated with the actions transforming one states set
into another (Volpentesta, 2014).
Figure 2: The NFC interaction graph.
Figure 2 illustrates the interaction graph for NFC-
triggered user interactions with simple services.
In (Volpentesta, 2014), the concept of interaction
pattern has been introduced as the basic structure of
chained actions that is common to all interactions
occurring in similar situations. In NFC-triggered user
interactions with simple services, it turns out that
interaction patterns are determined by two circuits in
the NFC interaction graph:
(u1,s11,s12,u2), associated to a proper
interaction;
(u1,s21,s22,u2), associated to an improper
interaction.
3.3 Interaction Information Flow
When an interaction pattern has been performed,
some information is exchanged between a user and a
simple NFC service. Given an interaction pattern, the
interaction information flow is a model of
information exchanged between a user and a simple
NFC service, during the execution of that interaction
pattern. Of course, it includes elementary data pieces
needed by the simple NFC service to be aware of the
current context situation.
As matter of fact, once the two NFC devices are
brought together, elementary data on states of
interface context items are exchanged between them
(in case of a proper interaction), and then transmitted
to the simple NFC service through a protocol other
than NFC.
The simple service receives such data and can be
aware (or recognizes) the current situation context
which is a snapshot of the states of interface context
items (relevant properties of the smart environment,
the system, and users). In order to do that, the simple
service generally makes use of context data coming
from other sources, a domain model (taxonomy or
ontology) of the interface context, and an inferring
capability (e.g. defining attributes and classes or
fusing current data into meaningful context
situations). Besides data on states of changeful items
of the interface context, user and service exchange
data of the following types:
Identity. It regards:
o User: personal data (name, age, birthdate,
etc.), activity-related data (personal schedules,
tasks, etc.), social-related data (community
membership, friends, organizational role);
o NFC target: NFC tag identifier and content
metadata, as well as other business and
physical data useful for a semantic description
of the physical object with the attached NFC
ICEIS2015-17thInternationalConferenceonEnterpriseInformationSystems
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tag (e.g. price, warehouse location, expiration
date, weight of a product);
o NFC reader: identifier and other device
metadata (device type, manufacture,
obsolescence, …), trust & security data
(access control, usage rights, …), functional
data (settings, network address, state and
capabilities, etc.);
o Simple service function: function control data
and metadata (function type, application
server, service provider, policy, …) including
a command to perform the function;
o Relationships: elementary data necessary to
derive relationships between user, interaction
resources and simple service (user access
level, user preferences, history patterns, etc.);
Location. It regards “where” the NFC interaction
occurs. The location data can be expressed as a
qualitative description (e.g. room or floor
reference) or as a quantitative information (geo-
location, distance from a known point, relative
position to known point);
Time. It regards time-related properties of
“when” interaction takes place. Temporal data can
be also used for a semantic interpretation of the
interaction moment (e.g. season, calendar events,
day time periods). Generally such data are derived
from the NFC reader internal date-time functions;
Environment. It regards environmental data (e.g.
temperature, brightness) coming from other smart
objects controlled by the NFC reader that send
them to the simple service.
4 A REAL CASE STUDY
As a partial validation of the model, we describe its
application in an ongoing project addressed to the
employment of NFC technology in regulating the use
of municipal parking areas in the city of Cosenza
(Calabria, Italy). Cosenza is a little town in southern
Italy; according to ISTAT statistics dataset
(http://www.istat.it) for 2012, Cosenza has a
population of 68,000 inhabitants; the number of
circulating cars is over 50,000, and there are 138 toll
parking slots per 1,000 circulating cars (7th place in
national ranking). A municipal agency is in charge of
management of the toll parking service in outdoors
parking areas (five areas with different payment
policy); it manages 140 working parking-meters,
equally distributed over the available parking areas.
Following the proposed model, we discuss the NFC-
based smart environment and the NFC-triggered user
interaction with two simple services that we have
conceived and developed in the project.
4.1 The NFC-based Smart
Environment in the Case Study
The NFC-based smart environment may be described
in terms of users, interactive resources and NFC
simple services.
Users. We have considered two different type of
users: the driver, who desires to use a parking area for
his/her car, and the parking officer, who’s in charge
to check if a vehicle is allowed to stay in a particular
parking area or not.
Interactive Resources. We have considered two
input resource types:
a) A couple of driver’s NFC-enabled smart phone
(acting as NFC reader) and NFC tag attached on
a parking-meter (acting as NFC target);
b) A couple of officer’s NFC-enabled smart phone
and NFC tag attached on the windshield of the
driver’s car.
Both NFC smart phones brought by the two class of
users are equipped with a peripheral device, working
as output resource.
NFC Simple Services. We have considered a driver-
oriented simple service and an officer-oriented simple
service that are fully described in the next subsection.
Each one of this two simple services is based on a pair
of a set of scripts running on the smartphone memory
(bundled as an app) and a remote REST API functions
that collects, filters and verifies the changeless states
of the current interface context items.
4.2 NFC-triggered User Interactions in
the Case Study
As we have discussed in section 3, the NFC-triggered
user interactions can be described in terms of
interface context, actions, and interaction information
flow. The interface context is formed by changeful
items (namely, distance, RF feedback notifier, and
service response notifier) and changeless items in the
interaction information flows associated to either the
driver-oriented simple service or officer-oriented
simple service. Therefore, in what follows we
describe actions and interaction information flow for
each of the two considered NFC simple services.
4.3 Driver-oriented NFC Simple
Service
4.3.1 Actions and Service Functions
The first user/driver action is to bring a couple of NFC
ModelingNFC-triggeredUserInteractionswithSimpleServicesinaSmartEnvironment
101
compatible devices together, see point a) in 4.1, this
action is triggered by his/her willingness to get
authorization for a parking space occupancy with a
car. This action changes distance item state from 0 to
1. In response to it, a service action may change the
state of RF feedback notifier, and service response
notifier. In case of proper interaction, an information
flow (states of changeless interface context items and
other data) is enabled between one of the two NFC
devices and the simple service.
The simple service checks user’s permission
rights and payment account, and then, it sends the
operation result to the user’s smartphone, via a
protocol other than NFC. Successively, the
user/driver separates the two NFC devices, and this
ends the match stage of the NFC triggered user
interaction. However, in order to complete the case
studio scenario, let us briefly describe the successive
usage stage. An authorized user/driver may interact
with the app on its smartphone in order to
acknowledge the simple service he/she wants to park.
At this moment, the simple service starts counting the
time the user’s vehicle remains stationary. The
user/driver can later interact with the app on the
smartphone in order to stop the timer at the moment
he/she wants to leave the parking lot. At this moment,
the simple service is capable to compute the amount
of parking cost depending on the elapsed time, the
parking zone cost-per-minute (related to the parking-
meter-id), and possible special user’s permissions
(resident permission, disabled person’s permission,
etc.). Lastly, the simple service deducts the parking
cost from user's payment account, and it sends back
to the user’s smartphone a receipt of the payment (via
a protocol other than NFC).
4.3.2 Interaction Information Flow
The interaction information flow consists of the
following changeless items data:
driver/user’s identity and an associated vehicle
registration plate number. These data come from
a local storage of the user’s NFC smartphone;
parking-meter identity and location. These data
are retrieved from one of the NDEF records
inside the NFC tag attached to the parking-meter;
parking starting time (the moment when the user
acknowledges the simple service he/she wants to
park). These data are derived from the internal
clock of the user’s smart phone.
4.4 Officer-oriented NFC Simple
Service
4.4.1 Actions and Service Functions
The first user/officer action is to bring a couple of
NFC compatible devices together, see point b) in 4.1,
this action is triggered by his/her willingness to check
the authorization for a car occupying a parking space.
This action is the same of the one described in
4.3.1, but it enables a different information flow
(states of changeless interface context items and other
data) between one of the two NFC devices and the
simple service. This information allows the simple
service to check permission rights for the car, and
then it sends the operation result to the user’s
smartphone, via a protocol other than NFC.
Successively, the user/officer separates the two NFC
devices, and this ends the match stage of the NFC
triggered user interaction. Lately, in case on
unauthorized parking, the user/officer may issue a
parking infringement notice.
4.4.2 Interaction Information Flow
The interaction information flow consists of the
following changeless items data:
user’s identity (i.e. officer’s identity). These data
come from a local storage of the user’s NFC
smartphone;
vehicle identity (registration plate number). These
data are retrieved from one of the NDEF records
inside the NFC tag attached to the vehicle
windshield;
vehicle location. These data are derived from the
internal GPS sensor of the user’s smart phone;
time of check (the moment when the user/officer
acknowledges the simple service he/she wants to
check the authorization for the vehicle). These
data are derived from the internal clock of the
user’s smart phone.
4.5 Case Study Validation
In order to complete early stages (conceiving and
developing) of our life cycle project, we have
conducted a basic empirical validation of the adopted
conceptual model and of the two simple services. To
this purpose, we have selected two traffic officers, ten
drivers (employers of the municipal bureau) owning
a personal Android NFC-equipped smartphone, and
three parking-meters near the city hall, where usually
the ten drivers get a parking when they go to work.
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The two officers were endowed with a specific model
of Android NFC-enabled smartphone with pre-
installed officer-oriented app, and we have instructed
them on how to use the app and how to use a
smartphone as NFC reader. Each of the ten driver was
given a car’s NFC sticker with general guidelines on
both how to attach the NFC sticker to the internal part
of his/her car’s windshield and how to download and
install the driver-oriented app on his/her own
smartphone. Each car’s NFC tag was encoded with
only one NDEF record for the car identity. For each
parking-meter, we have written two NDFEF records
(1 for the identity and 1 for the geo position) into a
NFC tag with a typical NFC “tap here” icon. Then,
we have asked a municipal operator to stick each NFC
tag on the associated parking meter. We provided
both officer-oriented app and driver oriented app with
an extra notification function in order to record
officer and driver actions in the match stage of the
NFC triggered interaction. Validation participants
were primarily required to interact with simple
service via NFC, but we also offered a fall-back
solution that allowed them to get service response
(checking-in for drivers, checking car permissions for
officers) by manually entering input data into a form.
Moreover, in case of manual input fall back use, we
proposed them a dedicated modal form on each app
in order to let them indicate the reasons why they
were not interacting via NFC.
In the app modal dialog, the user can choose
among these options:
A. Tag not found/not reachable: the user was not able
to find or reach the NFC target tag;
B. Tag unreadable: the user did not get any feedback
on the output resource after bringing together the
NFC reader and the NFC target tag;
C. Tag read error: the user did get an error feedback
on the output resource after bringing together the
NFC reader and the NFC target tag;
D. Other, specify later: the user will be contacted
after the validation period in order to know why
he/she chose the fall back solution.
We have been tracking app users actions and
collecting data over a period of four successive days
of December 2014.
Result analytics, shown in table 1, gives a first
insight on the usability/accessibility of the two NFC
simple services interfaces in novice users'
perspective.
Our validation has made it possible to simulate
and visualize requirements and high-level designs
very early in the project life cycle; this has pointed
out some decisions that should be taken about the
responsibilities and behaviour of model components,
and their interaction. In particular, the results yielded
by our early validation work have suggested:
• more effort must be dedicated to teach users on
using a smartphone as NFC reader, in order to
overcome their initial difficulties and inhibition
threshold;
• how the NFC tags are located onto parking-meters
is an important design issue to be considered to
facilitate driver NFC triggered interaction
(parking meter’s NFC tag should be clearly
visible and easily tapped);
• the app user should be aware where the NFC
reader antenna position is on the back of his/her
smartphone, otherwise he/she could have problem
in aligning NFC reader antenna with
correspondent NFC target one;
• before sticking the NFC tag on a parking meter,
the municipal operator should be aware that in
some positions the NFC tag antenna could
interfere with metallic parts of the parking meter
shell;
• additional instructions should be provided to
assist drivers in positioning the NFC sticker onto
the internal part of their car’s windshield in order
to facilitate officer NFC triggered interaction
(car’s NFC tag should be clearly visible and easily
tapped).
Table 1: Validation analytics.
officer
interactions
driver
interactions
TOTAL
82 87
NFC
74 75
Txt
8 12
% NFC
90,24% 86,21%
Opt A
1 4
Opt B
3 2
Opt C
3 1
Opt D
1 5
5 CONCLUSIONS
NFC-based smart environments establish an easy way
to embed the computation in everyday life
environments, as they facilitate the human interaction
with information and services. Such interaction is not
centralized in a single device, but any pair of
compatible NFC devices can potentially give an input
to a service. In particular, NFC-triggered interaction
with simple services does not require the user to
manually input values. The concept is that the event,
triggered by bringing together two NFC device in
close proximity, is translated into information making
ModelingNFC-triggeredUserInteractionswithSimpleServicesinaSmartEnvironment
103
aware the simple service of the current context
situation, and the service execution, depending on the
context and service characteristics, is reflected on a
corresponding activity in physical space.
In this paper, we have proposed a model of NFC-
triggered user interactions with simple NFC services.
The model is a conceptual tool readily applicable in
designing, analyzing and operationalizing human
interaction with real simple service applications in a
NFC-based smart environment. Although it has not
been completely validated yet, its usefulness has been
confirmed within the development of a project which
required the design of NFC-based interactions with
simple services for car parking management in a city
area. The model elements could be regarded as the
building blocks of interaction structures with
complex NFC services, where the service execution
could not deliver the expected result that fulfills user's
needs, requiring some more information than the one
exchanged during the NFC interaction with simple
services. The idea is that any interaction with
complex services can be regarded as a combination of
elementary structures identified by our model. This
lets us hope that our effort serves to open new
research avenues that could be taken in the future in
order to define a general model of NFC-triggered user
interactions with complex NFC services.
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