ABSTRACT
Both the idea and technology for connecting sensors and actuators to a network to remotely monitor and control physical systems have been known for many years and developed accordingly. However, a little more than a decade ago the concept of the Internet of Things (IoT) was coined and used to integrate such approaches into a common framework. Technology has been constantly evolving and so has the concept of the Internet of Things, incorporating new terminology appropriate to technological advances and different application domains.
This paper presents the changes that the IoT has undertaken since its conception and research on how technological advances have shaped it and fostered the arising of derived names suitable to specific domains. A two-step literature review through major publishers and indexing databases was conducted; first by searching for proposals on the Internet of Things concept and analyzing them to find similarities, differences, and technological features that allow us to create a timeline showing its development; in the second step the most mentioned names given to the IoT for specific domains, as well as closely related concepts were identified and briefly analyzed.
The study confirms the claim that a consensus on the IoT definition has not yet been reached, as enabling technology keeps evolving and new application domains are being proposed. However, recent changes have been relatively moderated, and its variations on application domains are clearly differentiated, with data and data technologies playing an important role in the IoT landscape.
METHODOLOGY FOR THE SLR
Figure 1. Flowchart for the search stage of the SLR
The studies selection stage of the SLR was executed following the flowchart shown in Figure 1. The quantitative results of executing both search strings are shown in Table. Main sources are listed first and sorted alphabetically. Classification is made accordingly to the most common names used for types of documents in the different sources. Totals for each source and type of document are indicated in italics in the rightmost column and bottom row respectively for each search string.
Table 4. Primary studies selection
Several documents did not provide enough information in the abstract or keywords to decide on either including or excluding them as primary studies. For these cases, a second step was performed, skimming through each document to get a clearer insight on its purpose. At the end, a set of two disjoint lists of documents {PJ, PC} was selected and its elements were used as primary studies for our SLR (Table 4), where PJ are the primary studies found in journals, magazines and reviews, and PC the ones found in conference proceedings and book chapters.
THE INTERNET OF THINGS CONCEPT
Table 5. Joy’s six Webs taxonomy
The notion of IoT has evolved since it was conceived in the late 1990s. Joy initially proposed it as part of his six Webs taxonomy (Table 5) in a speech at the World Economic Forum in Davos (Switzerland), which was later replicated as a lecture in several technological and academic forums. The sixth of such Webs is referred as device to device (D2D) and defined as an internet of sensors distributed across a mesh network, setting up urban systems for maximum efficiency.
Figure 2. Three main visions of the IoT
Atzori et al. discussed several interpretations and definitions of the IoT. They state the basic idea of this concept is the pervasive presence around us of a variety of things or objects such as RFID tags, sensors, actuators, mobile phones, etc., which, through unique addressing schemes, are able to interact with each other and cooperate with their neighbors to reach common goals. In their analysis, the IoT paradigm is depicted as the result of the convergence of three main visions: Things-oriented, Internet-oriented, and Semantic-oriented see Figure 2.
THINGS IN THE IOT
Figure 3. Capabilities of Internet connected devices as sets. The shaded area represents the set of Things in the IoT
Figure 4. Subsets of the IoT
Figure 3 presents an Euler diagram with the relationships between the capabilities of Internet connected devices. Devices with any of the capabilities in the shaded area of the diagram are considered part of the IoT. The diagram shows that any combination of the first four capabilities is possible, but having processing capabilities in things that can only be identified or located is not seen as an added value, as these types of things only share information about their characteristics or physical location, without creating or transforming data from their environment or received from the Internet. From this, four subsets that result of interest in the IoT are identified and shown in Figure 4.
OTHER NAMES GIVEN TO THE IOT
As section presents the names given to the IoT in such contexts, as found in the reviewed literature, accompanied by a brief description. Some of these names represent complete new concepts on their own, while others are mere specializations of the IoT.
The Web of Things (WoT) is a concept described in as making things web-present by embedding web-servers in them or by hosting their web-presence within a web server. The name was first used as part of Sun Microsystem’s project JXTA, defining a set of protocols for building applications and deploying them on a virtual network. More recently, Guinard and Trifa proposed an architecture for making devices an integral part of the Web by using HTTP as an application layer. In this context, the term Web of Objects is also used as well as Physical Web. It is important to note that all of the Web-based visions consider naming services of things as an important feature.
Extending from the IoT and the WoT, the notion of Wisdom Web of Things (W2T) represents a holistic intelligence methodology for realizing the harmonious symbiosis of humans, computers, and things in the hyper world. This concept relies on different abstractions of intelligence and the creation of knowledge from data. The word “wisdom” implies that each thing in the WoT can be aware of both itself and others to provide the right service for the right object at a right time and context.
DISCUSSION
Figure 5. Interaction between IoC and IoT devices
Figure 5 displays examples of devices and applications that can be found in each of these sets, sharing different types of data, like binary strings containing commands or raw data, documents in application-specific formats, or images. By means of their networking capabilities, elements in both sets can communicate to each other and take advantage of their specific characteristics and features, and the services they provide.
Figure 7. Concepts and notions used by authors in presenting their visions of IoT
In Figure 7, the most relevant concepts and notions that were used by authors in explaining their visions of IoT are listed. Terms like identification, location, tracking, and specific technologies like RFID were taken off the list as we consider they don’t provide additional information to what has been said before. Also, most of the authors make use of specific applications or whole application fields as to exemplify and describe the potential impact of the IoT.
CONCLUSIONS
The Internet of Things is the confluence of several technologies that allow providing Internet-based services and applications supported by electronic devices attached to physical things for acquiring data and controlling processes. As a general understanding, this phrase might well describe the IoT, but the variety of definitions and visions found in literature prove defining a complex technology or range of technologies is also a complex process.
However, though these definitions might appear as diverging, they are usually presented around five elements, occasionally including more than one of them: networking, services, communications, data and things. Earlier definitions were more commonly centered on networking aspects, while the most recent tend to be more comprehensive, as expected when a technology is in a maturing stage and its scope begins widening and more capabilities and possibilities are discovered.
Conducting a SLR on the concept of the IoT allowed us to obtain a clearer insight on this technology and what can be achieved through it. Observing the way these definitions have evolved and how different concepts, technologies and ideas have been incorporated as the IoT develops suggests that a correct description and characterization of the things at the end-points of the IoT should be one of the first goals towards a final definition. Latest efforts are paying more attention to things and what things can do as part of new services, applications and business models inspired by the IoT.
Several visions and definitions of the Internet of Things were found and analyzed. They can be categorized in different ways, as to how the technology is understood, which part of the IoT spectrum is the definition biased to, or the technologies that are mentioned as fundamental part of specific visions. These definitions are extended and complemented with specific terms of the different application domains of the IoT, often with designations that researchers adapt to each domain.
Source: Universidad Autónoma de Baja California
Authors: Jorge E.Ibarra-Esquer | Félix F.González-Navarro | Brenda L.Flores-Rios | Larysa Burtseva | María A.Astorga-Vargas
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