## 3 Data Interoperability Provisioning with Web of Objects
### Modeling Interoperable Healthcare Services with WoO  
Modeling healthcare services with WoO enables data interoperability in the heterogeneous healthcare environment and simplifies the integration of data using standard virtual object information models. Data collected from real-world objects in various healthcare settings are virtually digitized and semantically annotated into VOs. Healthcare data in VOs are accumulated and harmonized by the CVOs (Composite Virtual Objects), to extract high-level knowledge. An overall view of the multi-domain healthcare environment supported with WoO features for interoperability provisioning has been rendered in Figure 2. WoO features are equipped with the necessary data processing capabilities and interfaces to collect and process the healthcare data from multiple platforms. This design is based on a bottom-up style where data generated from various healthcare environments are gathered for processing at different levels. It follows the WoO reference platform to represent diverse healthcare data. VO data processing functions provide mechanisms to manage virtual objects. VOs are based on the semantic ontology, and they follow a well-defined information model which semantically annotates the data coming from the varied healthcare-oriented real-world objects. VOs are identified through unique Uniform Resource Identifiers (URIs). On top of the VO layer, CVOs form a composition of multiple VOs. In other words, one or more VOs are composed in a CVO to serve a service request. It is important to note that CVO not only provides a mashup of multiple Vos, but it also defines the set of rules that generate actionable information on VO data. These rules are triggered once the data from the VO satisfy the conditions already defined in the rules of each CVO. In multi-domain healthcare environments, it is necessary to support interoperability in case the data or objects can be reused in different domains. The semantic mediation model in our design incorporates a set of features that facilitate interoperable operations required to mitigate the heterogeneity of different domains. The healthcare data analytics and processing layer provide analytic functionalities. The analytics processing services are categorized into knowledge-driven and data-driven services. The knowledge-driven services process the semantic data models and use reasoning engine to infer the knowledge hidden in the semantic objects. In contrast, the data-driven services integrate learning processes to classify and predict the healthcare-related facts using deep learning algorithms. The top layer in the design is related to service management functions, which contains system-level functionalities. These include service request evaluation and analysis service, which processes the user request based on the user history and preference parameters and also considers user access level policy. The lifecycle management process handles states of different services in the system; it takes care of which services are in running state and which are halted due to the service load. The discovery process manages services availability by querying the service repository database. The service repository database provides the entries of all services available in the system. Whereas, the orchestration process is responsible for the composition flows of services and their configurations. Besides, virtual object data processing functions manage VOs, which digitally represent healthcare objects with their descriptive semantic information. The VO representation model is necessary to describe the healthcare data object properties that can be associated with VOs. It includes different types of metadata including VO description, its interface information, its functions, features, and  
Figure 2: High level design of interoperable healthcare services with the Web of Objects (WoO) model. profile. The VO representation model describes the entities to be used by CVOs and services in the WoO domain.