Machine readable

Green application systems need to take advantage of environmental information to enhance the interaction with the user. For example, environment monitor applications should be able to deal with fusion of multi-sensor data. Sensor data cover multiple aspects of the environment, such as the location, identity, temperature, humidity, pressure, brightness, activity and state of people, groups and objects, and so on. Many of the captured data are analogous in nature making the chance of finding a specific term quite good. However, the integration of heterogeneous sensor data into a single system can be difficult.

One of key characteristics that green applications should possess is the ability to acquire information from heterogeneous sources, perform context interpretation and carry out dissemination of context to interested parties. Each device or subsystem in the application might contain a set of variables to accommodate raw data about its surrounding environment sent by sensors or other devices. It, however, lacks a well-developed mechanism for defining sensors, their attributes and classifications. It also does not have a standard high level language to prescribe the required inputs and outputs as well as to control their actions.

Green applications acquire information from surrounding environments through sensors or from other information systems where the events take place. It needs to establish an information and knowledge level of collaborative grid among green computer systems to share and reuse machine-interpretable conceptualizations to maximize their utilities. The realization of semantic web and ontology is one of most promising approaches to meet this need.

There are a number of languages available for representing the concepts in ontology e.g. RDFS (Resource Description Framework Schemas), OWL (Web Ontology Language), and OWL-S. Ontologies provide end-user service and ICT

support system developers a common base for efficient and effective services definitions as well as integration and utilization of ICT systems and resources.

Therefore, a solution to integrate the data from multiple sources or interpret the semantic of heterogeneous sensors with different capability is needed in green application systems. To support these tasks in a context-awareness system is needed and more often it is based on ontologies that enable reasoning automatically and efficient knowledge sharing from traditional stand-alone systems to the highly distributed green ICT system.

There are many standards and middleware equipped with different protocols such as Java Intelligent Network Infrastructure (JINI), Home Audio/Video Interoperability (HAVi) and Universal Plug and Play (UPnP), and Open Service Gateway Initiative (OSGi) for connecting heterogeneous systems. JINI, however, cannot directly interact with some devices such as TVs due to lack of HAVi. Although it can use a service gateway to control and connect different appliances, it leads to different levels of difficulties in usage and maintenance. These technologies offer different alternatives for interconnecting heterogeneous devices and services. UPnP supports ad-hoc networking for devices and services, and it is easy to develop. OSGi specification defines a service framework to support multiple Java based devices to run collaboratively, so a new device can be easily added to an executable environment using plug-play technology in order to increase flexibility and dynamics of a system.

1. Remote Method Invocation (RMI)

Remote Method Invocation (RMI) is a Java application programming interface that is equivalent of remote procedure call (RPC). RMI enables a client to obtain a reference of the remote object and to execute it. RMI with IIOP protocol provides the core interfaces and mechanisms for the client and server to communicate through stub and skeleton objects. Even though it has naming service to search the required objects,

semantics for naming service is not supported. Besides, it only supports interoperability between JVMs, non-Java embedded systems have difficulty to participate.

2. CORBA

CORBA, proposed by OMG, provides technical standards for integration and collaboration for heterogeneous application systems. Distributed software based on CORBA objects can increases its reusability and expandability. Many researchers take the advantages of these features to develop middleware environments to support large scale distributed applications. The Interface Description Language (IDL) is a programming language independent specification to describe the interface for client and service communication, so CORBA supports multiple languages and platforms.

CORBA was widely accepted technologies by academic and industry communities, but it lost its popularity due to its complexity and industry commitments.

3. JINI

JINI based on the Java technology was developed by Sun Microsystems for spontaneous services and resources networking. JINI provides the ability to assemble service component and cope with distributed computing.

4. HAVi

Home Audio Video Interoperability (HAVi) is a standard specification for connection, communication protocols and APIs that allows Audio and Video hardware products from different vendors to be networked together and controlled from one primary device. HAVi offers plug-and-play capabilities for smart home configuration and it models home networking services as software element. Each object has a unique name and identifier. Objects use messaging to request services from other objects. The advantage of HAVi is that it can bridge with JINI to extend its greater services. The problem is that the actual message passing may differ between vendors.

5. UPnP

Universal Plug and Play (UPnP) is Microsoft peer-to-peer networking initiative.

UPnP supports ad-hoc networking for devices and services, and it is easy to develop.

Further, it has minimal configuration requirement, and its automatic discovery process uses IP address which is compatible with the existing protocol such as TCP/IP, UDP, HTTP and XML, so a device can leave the network smoothly and automatically. Both controllers and devices can be implemented on a variety of platforms including personal computers and embedded systems.

6. X10

Power-line networking is increasingly becoming an important component for home networking systems. X10 is a standard for communication among electronic devices which are used for home automation using power-line wiring for signaling and controlling. It belongs to horizontal integration between physical devices.

7. OSGi

The protocols mentioned above are not compatible with each other due to their design, so without introduction of extra mechanism to them the communication among them is impossible. The Open Services Gateway Initiative (OSGi) is a universal middleware supported by industry paving a standard way to connect devices such as home appliances and security systems to the Internet. OSGi framework can integrate popular protocols such as UPnP, Jini, DPWS, Zigbee, and Bluetooth. With the application of extensible technologies based on OSGi framework and the supports of context-awareness mechanism, ‘off-the shelf’ affordable smart house could become available to the market, so the user can install monitoring devices or others without the aid of engineers.

Green ICT system could shift its focus on the adoption of service-oriented architecture for system design and implementation to alleviate the insufficiency in

integration and interpretability. They also need to transform traditional tightly coupled modules into more loosely coupled services. Although they need to sense environmental changes, receive messages from other sub-systems, and produce appropriate responses, they need to have capability to reallocate their resources dynamically according to demands and priorities. In such heterogeneous systems, the resources which could be software or hardware can be considered as services. The software would be composed by a number of other software components to perform certain functions. The hardware can be devices such as smart lighting, smart table, or sensors which are responsible for controlling environments and collecting information about changes.

Service-Oriented Architecture (SOA) offers a practical and viable approach to implement services. The key advantages of Web services provide capability for developers to create applications through reuse of existing loosely coupled components and utilization of Web protocols and open XML standards to enable interoperability between systems. From service consumers’ point of view, it is important for service consumers to answer three questions: what services are required;

where they are located; how the service can be invoked. In other words, there are three questions corresponding to three key mechanisms service discovery, service selection, and service composition in SOA. Similarly, service consumers could be an end user or a service. In this section, we discuss four major characteristics and research directions. Four major characteristics are composed of framework, middleware, automatic control, and semantic sensor network.