2014 IEEE World Forum on Internet of Things (WF-IoT)
Short Paper: Semantic URI-based Event-driven Physical Mashup
Sejin Chun1, Jooik Jung1, Xiongnan Jin1, Gunhee Cho1, Jinho Shin1,2, and Kyong-Ho Lee1 Department of Computer Science, Yonsei University1 Mobile Communication Division, Samsung Electronics2 Seoul, Republic of Korea {sjchun, jijung, wnkim, ghcho}@icl.yonsei.ac.kr,
[email protected],
[email protected] II.
Abstract—To enhance the integration of different IoT application domains, we propose a two-layered IoT information model that consists of domain-independent and domain-specific models. In addition, for the meaningful composition of things and their services, a semantic URI as a unique identifier is allocated to a thing. Finally, a modeling approach of constructing physical mashups is proposed for the event-driven composition of IoT services. In order to show the efficiency of the proposed eventdriven physical mashup approach, an energy management scenario in u-campus is demonstrated as a case study. Keywords— Internet of things; physical mashup; complex event; semantic URI; conceptual model
I.
INTRODUCTION
The Internet of Thing (IoT) indicates a hyper-connectivity of things on the Internet where distributed participants— humans, things, and services—are connected through a variety of relationships. One of the challenging topics in IoT is how to put the things together in order to compose a new type of IoT composite services, which are called physical mashups [1]. In recent studies, Stephan et al. [2] have studied information models in pursuit of the convergence of IoTs. However, the existing models do not support various events, which are generated by things and trigger service execution. An event is one of the required components for facilitating complicated IoT services such as physical mashups. Especially, the mashup must be able to grasp the IoT information ecosystem with relationships among IoT components such as events, resources, entities and services. To construct an event-driven physical mashup, efficient mashup modeling and object discovery methods are required. In the object discovery, an integrated identifier, which is uniquely assigned to IoT objects, is a fundamental step to explore the object across different domains. For providing the mashup modeling to a user, a graphical representation of describing the mashup is a necessity to simplify the understanding of its data flow and control structure. With these requirements, we propose an extended IoT information model that consists of two layers: domainindependent and domain-specific models. We also propose a method of allocating semantic URIs, which promote the discovery and integration of things across different domains. To model an energy management service in a campus domain, an efficient approach to modeling a mashup is proposed.
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IOT INFORMATION MODEL
In this section, we propose a domain-independent model that allows the abstraction of IoT components. Also, we develop a domain-specific u-campus ontology derived from the proposed domain-independent model. Our domain-independent model is an extension from the conventional IoT domain model proposed by Stephan et al. [2], which is composed of five core concepts such Entity, Resource, Service, User, and Device. However, with their generic model, it is impossible to express various events, which represent contextual changes within an IoT environment. In order to resolve the limitation, we extend the generic model to incorporate an event concept and its relationships with other existing concepts. An event as an extended concept is defined as follows. x Event: represents a status of a meaningful change in IoT environment. Events are defined by using an event language and a resource is the factor of an event. An event decides whether to trigger a specific service. Specifically, the Event model modifies the LODE ontology [3] to fit the proposed domain-independent model. This event ontology contains six properties to define a specific event. First, the atPlace property is represented with a form of latitude, longitude, and altitude. The inSpace property describes a location based on a location ontology. The atTime property describes the time or the interval of time by utilizing a temporal-entity of the W3C time ontology. The involved property expresses a real-world object, which participates in an event. The triggers property decides which service is triggered by a specific event. Lastly, isFactorOf indicates which resource is a cause of an event happened or to happen. The u-campus ontology as a domain-specific model, which is derived from the proposed IoT information model, is as shown in Fig. 1. Within a campus, entities may be buildings, classrooms, laboratories, and so on. They may also be projectors, computers, smart gateways, etc. It is worth mentioning that a smart gateway that provides access to non-IP based entities is also represented. Campus devices, which are attached to entities, are categorized as sensors, actuators, and tags. The ontology provides various campus services such as a device control service, and so on. Campus resources can be lamps, door resources, and so on. Events happened in a campus include appliance events, sensor-related events, and on-campus festivities.
2014 IEEE World Forum on Internet of Things (WF-IoT)
Fig. 1. A ppart of a u-camppus ontology
III.
SEEMANTIC URI-BASED PHYSIC CAL MASHUP
In this sectioon, we proposse a semantic URI(S-URI) based meethod of moodeling physiical mashups.. The purpose of asssigning S-URII to an object is i to distinguissh its unique ID and to provide an inntuitive underrstanding of thhe object typee. The prooposed modelling approach enables a useer to easily crreate a phhysical mashupp by using grapphical componnents. When a reaal-world entitty is registerred into a service dirrectory that m manages IoT obbjects, S-URI that encouragges an exxploration of thhe entity is asssigned to the entity. An enncoded version of S-UR RI, which simpplifies S-URI innto a numeric form, cann infer variouus relationshiips among onntological conncepts. Thhe proposed sccheme of S-UR RI is as follow ws: htttp://{PONS}/{{DL_ns}/{DL__cls}/{DM_nss}/{DM_cls}//{TID} PONS indiccates a host name of thee service direectory. DL L_ns and DL__cls indicate thhe namespace of Dolce Ultrra Lite onntology (DUL)) [4] and the cooncept of an enntity from DU UL. As a high-level onntology, DUL L is used forr integrating other doomain ontoloogies. DM_nns and DM__cls indicatee the naamespace of a domain onttology and thhe selected doomain concept of an eentity. TID inddicates a uniqque object idenntifier thaat is assigned by the Univerrsally Unique Identifier algoorithm (w www.ietf.org/rffc/rfc4122.txt)). The proposeed directory ssupports the m modeling of eeventdriiven physicall mashups. A An example of campus eenergy maanagement sceenario is as foollows: “Varioous devices suuch as proojectors, compputers, air connditioners andd lights are loocated insside a classrooom. This partiicular classrooom is equippedd with a ddoor sensor, w which checks w whether the dooor is open or closed, c annd a motion deetecting sensoor, which deteermines whethher the claassroom is vaacant or not. In particularr, an adminisstrator reccognizes a prooblem that most of the devicces in the classsroom aree operating eeven though tthe room is vvacant. In ordder to haandle this situaation, the adm ministrator wiishes to constr truct a maashup service which shuts ddown all devicces in a classrooom if it iis empty for m more than 30 m minutes.” Fig. 2 illustraates a visual m modeling of a pphysical mashhup for haandling the aboove scenario. The notationss used in this figure aree extended froom the Busineess Process Modeling Notattion to fit the proposedd IoT information model. Specifically, while enntities (displayyed in rectanngle), resourcces (hexagon)) and devices (trianglle) are moddified, tasks, events, gateeways, asssociation arroows, and sequuence arrows stay remained. By usiing associatioon arrows, w we describe w which resourcees are utiilized by an evvent and whichh services utiliize resources.
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Fig. 2. A grraphical represenntation of a phyysical mashup
IV.
RELLATED WORK
Many of thee IoT system ms [5] do noot use a com mmon infoormation moodel but defines conceppts and relaations diffferently. To promote p the unification off informationn, the reseearch of [2] hhas proposed aan IoT information model w which inclludes entities,, devices and services that access a resoource. How wever, this m model cannot ssupport the reppresentation of o the deteection, consum mption, and reaaction of compplex events. A lot of IoT T applicationss use URIs aas an identifier to adddress IoT objeects. While soome of them allocate a unnique idenntifier, others extend URIs with meaninggful structure.. The entiity naming syystem proposeed by Bouquet and Molinarri [6] sugggests an objecct identifier that combines thhe two approaaches. Desspite the effoort of the research, their iidentifier doess not com mpletely refleect on variouus advantagess derived froom a connsensus betweeen the two appproaches. ACKNOW WLEDGMENT Thiis research waas funded by the MSIP (M Ministry of Science, ICT T& Future Plannning), Koreaa in the ICT R& &D Program 2013. 2 RENCES REFER [1] [2] [3] [4] [5] [6]
D. Guinard, V V. Trifa, T. Pham m, and O. Liechhti, “Towards phhysical mashups in thhe web of things,” Proc. Internaational Conferennce on Networked Sennsing Systems, pp. 1-4, 2009. H. Stephan, S. Alexandru, A B. Maarin, and C. Franccois, “A Domain M Model for the Internet of Things,” Proc.. IEEE iThings, ppp. 411-417, 2013. LODE ontologyy, http://www.linkkedevents.org/ Dolce Ultra Litee Ontology, http:///www.loa.istc.cnnr.it/DOLCE.htmll K. Kenda, C. F Fortuna, A. Morraru, D. Mladenic, B. Fortuna, annd M. Grobelnik, “Maashups for the Weeb of Things,” Prroc. Semantic Maashups, pp. 145-169, 20013. P. Bouquet andd A. Molinari, “A A global Entity Name N System (EN NS) for data ecosystemss,” Proc. VLDB, ppp. 1182-1183, 2013.
