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Building the Mobile Computing Environment 677 using barcode drawer for none control to generate, create none image in none applications.qrcode c# library 32.4 Scientific theories vs. practical implementations Java programming language Context-aware services a nd computing is an established area of research within computer science in general and data communications and human-computer interaction in particular. Computer and behavioral scientists have explored the concepts of applications (or set of applications) dynamically being adapted to context from several different perspectives for over a decade. However, up until now, no one has succeeded in harnessing this powerful concept as a commercial product and brining it to market.

Technology has developed in the direction of context-aware services by several related strands of research, beginning with Weiser s (1991) vision of ubiquitous computing (now often referred to as pervasive computing ). Additional research communities have been created around further developments such as augmented reality (Mackay et al., 1993) tangible interfaces (Ishii, 1997), wearable computers (Bass et al.

, 1997) cooperative buildings (Streitz, Konomi, and Burkhardt, 1998), etc. Today, annual conferences on ubiquitous computing are organized around the world. Context awareness is fine in theory.

The issue is figuring out how to get it to work in practice. There are a number of areas where theory and a practical solution come into conflict with each other. In this section, we will bring up the three most challenging areas.

The first challenge is that context-aware computing completely redefines the basic notions of interface and interaction. Research questions abound: What role does context play in real-world tasks How can this be extended to a technological domain What can the computation really do for end-users How can end-users interact with a representation of context and yet maintain adequate control How can software make end-users both more productive and less consumed by the technology itself Appear s way of solving this issue is to have a user process that complies with all of the mobile requirements presented above providing an understandable and easy to use client interface. The second challenge is to find a trade-off between which tasks that can be handled by the administrator and which is best handled by the system.

Context-awareness quickly becomes an administration nightmare if the whole process of setting up a valid context set. As an example let us assume that we have one context parameter in the context domain, with ten different values. This is definitely not very hard for an administrator to map up and create relations for, however as soon as this number grows it quickly becomes very hard to oversee the administrator model.

Just when the context parameter has grown to three (with each giving 10 values) this increases to a 1000 permutations for the administrator to handle. The other extreme view on the problem is to have a context aware system derive all possible relationships in the context domain and let the context engine perform matching against this set of relations compared to the criteria s set for each service. The problem with this approach is that this is increasingly difficult as the number of parameters grow.

In the real world, one has to factor in hierarchical relationships of the objects of various parameters and cost of computing in a distributed network. Appear s way of solving this issue is to take out the domain specific knowledge from the computing problem and hand this to the administrator and then transform this administrator model into domain rules for the system to obey by. This gives the administrator control over the process and provides boundaries for the system to operate on.

Even with these boundaries it still is a heavy computing load the context-aware system has to perform, which made the introduction of parallel computing necessary. The main factor determining the workload is. 678 Building the Mobile Computing Environment the number of context pa rameters and the number of devices that exists in the system. Together with the third challenge Appear has chosen a distributed architecture to cope with these challenges. The third challenge is the problems of creating a flexible enough solution to support incorporation of these features into existing telecom and Internet infrastructure.

Appear realized these fundamental problems early on in the commercialization of its technology and concluded that solving these would be top priority and yield considerable competitive advantage. Appear decided that the most promising approach to context-aware computing was a distributed software architecture where responsibility for gathering, processing and usage of context parameters would be divided between several different network components, now aptly named Appear Server, Appear Proxy, Appear Publisher and Appear Client. Around these components a model of context awareness and context-aware services was created, where real-world Internet and wireless networking issues could be handled through configuration of the basic components.

The Appear Server is the central point of administration, where all configurations, statistics and device sessions are kept. The Appear server is the organizer of the system. However, during run-time the Appear server has a minimum number of operations to perform, with the exception of organizing the other components.

The Appear Proxy is the run-time engine in the system. All processing and run-time operation is conducted by the proxy. In order for the system to work properly each proxy needs to be able to operate without the other proxies in the network.

The Appear Publisher is the smallest components in the system, and is normally placed together with the Appear Proxy. The Appear Publisher has two main functions; (1) to detect when new devices comes into the new network, and direct them to the closest Appear Proxy, and (2) to alert the Appear Client of real-time changes of the Context Profile and Context Domain. The Appear Client is the end-user interface that performs all Contextaware operations on the end-user device.

. 32.5 Context-aware Over- none none the-Air Service Provisioning (OTA). Context-aware Over-the-A ir Service Provisioning is a distribution mechanism for provisioning services based on a Context Profile. The distribution can be both pushing services to the devices, or to provide the end-user with a description of the tools that are available to the end-user. In either case the distribution mechanisms need to be fully automated, using client-side intelligence to install, configure and when necessary delete services for the users.

Due to the differences outlined above, Context-aware service provisioning solutions must be adapted to small screens and easy to use while on the move. The Appear Client is adapted to these criteria, however the services provisioned by the system also need to be adapted for these new form factors, in order for the services to fulfill the mobile user s requirements. Last but not least, they must also be able to take the new dimensions of physical location, time, and other tailored contextual parameters into account when distributing services; some services may be exclusively provided only in certain areas or to certain types of users and a certain time.

Combinations of these parameters become.
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