Pervasive systems

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PART 1: Critical Evaluation of Fundamental Properties of Pervasive Systems

Q1: Discuss whether a pervasive system must fully support all the five properties: distributed, iHCI, context-aware, autonomous and intelligent.

A1: To begin with define what is pervasive computing?

"Ubiquitous computing is the method of enhancing computer use by making many computers available throughout the physical environment, but making them effectively invisible to the user".( Weiser 1993).The goal of pervasive computing is to make people thinking about the task rather than the tool of computer.[1]

As ( Weiser 1991) set there are three main properties of pervasive system they need to be support and he adds another two properties as additional properties.

1- Distributed: -Multiple systems work together and appear to users as one system.

These are key properties of distributed system:-

1-1 Networked:- ubiquitous computers are networked computer. They give different services either locally or remotely access. Such as WAN and WLAN network.

1-2 Transparency:- it does not mean that no one can see it or touch it but its presence does not intrude into the environment of the work.

1-3 Openness:- helps systems to avoid having to support all of their tasks at the design time. There are different degree of openness can be supported by distributed system.

For example, UbiCom camera can be use to do a printing service by transfer its data to the printer .[2]

2- Implicit Human-Computer Interaction (iHCI)

Much of human interaction need to be more hidden. Also more functions are automated.

The properties of (iHCI) are

2-1 The Calm Computer.

2-2 Implicit Versus Explicit Human-Computer Interaction.

2-3Embodied Reality versus Virtual.[2]

3- Context -Awareness:- allow applications to be able to sense the environment and use different information to adapt their behavior.

The properties of Context-aware are

3-1Three main Types of Environment Context: Physical, User, Virtual.

UbiCom systems focus on the physical world awareness.

3-2 User-Awareness [2]

Two additional properties which allow pervasive system to work in further environments

4- Autonomy: - this property enables systems to manage its own tasks without any intervention independintly.

The properties of Autonomy are

4-1 Reducing Human Interaction

4-2 Easing System Maintenance

5- Intelligence :- managing actions and interactions by making intelligent decision .[2]

There are many kinds of pervasive systems depending on the number of properties are support and interlink.

There are different views of pervasive system properties for examples:-

* Arts and Roovers (2003) identify five features of ambient to be contained, context-aware, personalised, adaptive and anticipatory.

* Buxton (1995) set two properties of pervasive systems to be support ubiquity and transparency.

* Enders et al (2005) categorized three kinds of pervasive system distributed, intelligent systems and augmented reality.

* Milner (2006) considers two types of pervasive system autonomous systems and iHCI.[2]

Poslad (2009,p36)suggests "The ideal type of ubiquitous computing is where all the properties

Of ubiquitous must be fully supported: it may not be required, useful or usable in many cases in practice, to support the full set of these properties".[2]

As Poslad(2009) mentioned there are different levels of support by pervasive system for each pervasive computer property .'level 1(minimal),level 2(basic),level 3(medium),level 4(high),level 5(full)'.The level of support could be help to know the level of maturity. The use of these properties may have medium or minimal support for some of these properties it is not compulsory to support the full level for all properties.For instance,location system application for a mobile user may designed to support medium level of distributed property.[2]

Q2: Critically analyses whether these properties are independent or interlinked?

According to Poslad(2009) There are different degrees of interlinked between these properties and depending on these degrees there are many possible of sub-types of pervasive system.

Q3: Contrast ubiquitous computing, Virtual Reality and Augmented Realty?

Virtual Reality is opposite of Ubiquitous computing as Weiser compared between them. Ubiquitous computing puts the use of computer in the real world with users and allow computer to live with them.

Ubiquitous computing is a difficult incorporation of human factors, computer science, social sciences and engineering. Virtual Reality lets people set in a computer-generated world .Also virtual reality often defined by one system which has different reality than the physical world.Agood example for virtual reality is playstation game where you can live in a virtual world

Which may simulate the real life.

Augmented reality is described as being in a physical environment which can has connection between physical objects with a virtual environment. Augmented reality can improve physical reality by adding virtual views to it. Augmented reality can be considered from both a Human-computer interaction and from physical world interaction.An example of Augmented reality is virtual views mixed into alive show of the real world.[2][3]

2 PART II: Analysis and Critical Review of the Technologies used in Pervasive Systems

Q1: Compare and contrast the different methods of location determination with regards to accuracy, indoor and outdoor, and local versus global location determination?

These are several basic location determination methods (Hightower and Borriello,2001):-

1- Triangulation:- One of the most general method .

The technique using in this method is to calculate the distance between known points by using some of distance measurement(lateration) or by measure angles(angulation). This technique has some systems work indoor and other systems work outdoor.

Lateration and angulation are usually together to know where an object is and from which orientation it is viewed. An example of triangulation is VHS omni-direction Ranging (VOR) system which used for aircraft navigation .It use angulation method with 1radial accuracy and precision equal 100 percent. VHS is outdoor system.GPS is another example of triangulation using lateration method.The accuracy of GPS system is 1-5 meter but it has low accuracy in bad weather .GPS does not work indoor.

2- Proximity:- It is location technique when an object is near a known location.

Proximity is indoor technique .For example active badges which developed at AT&T Cambridge. Active badge provide complete location information .The accuracy of active badges is room size. But active badges have difficulty with sunlight or fluorescent light.

Another example of proximity is automatic ID system which use automatic identification system such as, credit card .The accuracy of this system is range of sensing phenomenon .

Another location system using this technique is smart floor, fixed sensors inside the floor to recognize where the footsteps are? The advantage of this method is people do not need to carry any device or wear tags. However, it is a very expensive system.

3- Scene Analysis:-

The technique using in this method is use features of scene observed from specific markers that can help to recognize and store the location of objects in the scene. The pro of scene analysis is an able to define the location of objects using passive observation and features that not communicate with the distance or the angel of the objects.An example of scene analysis technique is RADAR which can measure object within 3 meters of their actual place with 50 percent precision. While Radar's lateration implementation has 4.3-meter accuracy at the same precision. Even though the scene analysis technique has greater accuracy than lateration technique.

The table below compare different location systems with regard to technique, accuracy and precision.




Precision %


Radio Time Of Flight


1-5 meter


Active Badge


Room Size



1 Radial




4x4ft regions



Scene Analysis, Triangulation



Smart Floor


Spacing of pressure sensors




150-300 meter


Q2: Give a critical review of privacy and security issues in pervasive systems?

Privacy and security are a big issue in pervasive system because pervasive system has some personal information such as location and it will be abused if someone uses this information in wrong way, such information need to keep in secure places .[4]

According to Satyanarayanan (2001) he points that because of serious loss privacy in pervasive system it may cause to reduce the number of knowledgeable users from using pervasive system. Satyanarayanan agrees that "Privacy and trust are likely to be enduring problems in pervasive Computing".[5]

It is necessary in pervasive system to have a flexible method for controlling and defining security policies. This policy will help administrators to identify and realize rules for greater control in their system from any entities behavior. Also it is important to deal with privacy and security problems in pervasive system to specified the guarantees in pervasive system environment from early into the design process.[7]