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Embedded Control Systems Design/Learning from failure

An engineer has to keep in mind that every device he or she creates will eventually fail. Catastrophic failure should be avoided by all means since this could result in injury or even death. Some main causes of engineering failures are insufficient knowledge, underestimation of influence and ignorance or negligence.

In this chapter some examples of catastrophic failure are given. By studying these examples the engineer can learn how to avoid failure in his or her designs.

Patriot
On February 25, 1991, during the Gulf War, an American Patriot Missile in Dharan, Saudi Arabia, failed to intercept an incoming Iraqi Scud missile. The result of this failure was the death of 28 US soldiers.

Problem
The cause of the problem is located in the computer responsible for the tracking calculations of the incoming Scud missile. This computer keeps time as an integer value in units of tenths of a second, and stores it in registers of 24 bits long. Afterwards, this value is multiplied by a fixed-point 24-bit representation of 0.1 to obtain a 48-bit floating-point value of time in seconds.

The failure is caused by the 24-bit representation of 0.1 in base 2. The base 2 representation of 0.1 is nonterminating: 0.0001100110011001100110011001100.... The 24 bit register in the Patriot stored instead 0.00011001100110011001100 introducing an error of 0.0000000000000000000000011001100... binary, or about 0.000000095 decimal. This means the accuracy of the time is reduced by 0.0001%.

However, the tracking of a missile doesn’t depend on the absolute clock-time, but rather on the time that elapsed between two different radar pulses. Since this time difference is very small, the error of 0.0001% is truly insignificant. This doesn’t explain the deviation of the Patriot missile, but there is a second problem.

The software used by the computer was written in assembly language 20 years ago. It was updated several times to cope with the high speed of ballistic missiles, for which the system was not originally designed. One of these updates contained a subroutine to convert clock-time more accurately into floating-point. However, the subroutine was not inserted at every point where it was needed. Hence, with a less accurate truncated time of one radar pulse being subtracted from a more accurate time of another radar pulse, the error no longer cancelled.

At the time the Scud missile arrived, the computer had been active 100 hours, so the calculated elapsed time had an error of 0.000000095×100×60×60×10=0.34 seconds. A Scud travels at about 1676 meters per second, and so travels more than half a kilometer in this error time. This was far enough for the incoming Scud to be outside the "range gate" of the Patriot.

Solution
The solution to this problem was already suggested before the accident. Increase the accuracy of the time representation, by the use of more bits. However, this solution avoids the problem from happening, but doesn’t solve it. If the computer is activated for years without rebooting, the same failure can still occur.

There is a better approach. Simply measure the relative time between the two radar pulses. The clock should always be reset at the first pulse and stopped at the second pulse. This avoids the subtraction of two almost identical big numbers, and its numerical problem.

Lesson

 * An algorithm where big numbers are subtracted from each other should be rewritten to avoid this loss of numerical accuracy.
 * It’s important to analyze the number of bits used to represent physical parameters, i.e. time, in the design.
 * The system designer needs very detailed specifications of all the components he uses.

Mars Pathfinder
On July 4, 1997, the Mars Pathfinder successfully set foot on the Martian surface. However, a few days after the start of its mission, the vehicle started losing information due to several system resets. The cause of this problem was located in the embedded systems kernel used in the Pathfinder.

Problem
The tasks of the spacecraft are executed as threads with priorities, reflecting the urgency of each task. There are 3 types of threads:

 * high priority threads, i.e. the bus management task.
 * medium priority threads, i.e. the communications task.
 * low priority threads, i.e. the meteorological data gathering task.

During execution of the bus management task, it will move data in and out of the information bus (the bus that connects all the components of the spacecraft). Access to this bus is synchronized with mutexes. The meteorological data gathering task uses the information bus to publish its data. When publishing, it acquires a mutex, writes to the bus, and releases the mutex. Using the mutexes guarantees that each bus thread waits until the previous one is finished.

Normally, the threads system with priorities and the bus management with mutexes works fine. However, a problem known as priority inversion can occur. Assume that a medium priority communications task is scheduled while the high priority bus management task is blocked waiting for the low priority meteorological data thread. The communications task, having higher priority than the meteorological task, would prevent it from running, consequently preventing the blocked bus management task from running. Since the communications task is a long-running task, a watchdog timer will eventually go off, noticing that the data bus task had not been executed for some time. The watchdog task will conclude that something had gone wrong, and initiate a total system reset. This reset is comparable to a home computer reboot; it clears the registers so that the system can restart without errors.

Solution
There are several solutions available for this problem. One of these is called priority inheritance. The meteorological thread will inherit the priority of the bus management task, causing it be scheduled with higher priority than the communications task.

Fortunately, VxWorks contains a C language interpreter intended to allow developers to type in C expressions and functions to be executed on the fly during system debugging. After uploading the right program to change the software of the spacecraft, the problem was solved.

It’s important to realize that priority inheritance is not the best solution to this problem. In complex systems, with dozens of bus tasks interacting, all the tasks will eventually obtain highest priority, and the problem remains. However, in case of the Pathfinder, it sufficed.

Lesson

 * Coordinate tasks by the use of priorities is not the best approach. This indirect way gives the scheduler all responsibility. It’s better to include the coordination in the system itself.
 * It is important to provide support to intervene when unforeseen errors occur.
 * the watchdog: every ECS should contain a watchdog task, because a system block can never be excluded.
 * debugging facilities in the field: without the ability to modify the system in the field, the problem could not have been corrected.
 * It is not possible to test every situation completely. If timing (coordination) is important, the amount of bytes is important,…, debugging can always be necessary.
 * Good theory is important: the theoretical solution for this problem was presented in a paper many years ago.
 * Correctness is important: the engineer's initial analysis that "the data bus task executes very frequently and is time-critical -- we shouldn't spend the extra time in it to perform priority inheritance" was wrong. It is precisely in such time critical and important situations where correctness is very important, even at some additional performance cost.

Ariane 5 Flight 501
TheAriane 5, Flight 501, was launched on June 4, 1996 and was the first unsuccessful European test flight. Due to a malfunction in the control software, the rocket veered off its flight path 37 seconds after launch and was destroyed by its automated self-destruct system when high aerodynamic forces caused the core of the vehicle to disintegrate. It is one of the most infamous computer bugs in history. What could be the reason behind the sudden change in flight path of the first flight of the Ariane 5? Certainly, reusing similar software code as in the previous Ariane 4 project without simulating was a big mistake.

Problem
An operand error occurred due to an unexpected high value of an internal alignment function result called BH, Horizontal Bias, related to the horizontal velocity sensed by the platform. This value is calculated as an indicator for alignment precision over time. The value of BH was much higher than expected because the early part of the trajectory of Ariane 5 differs from that of Ariane 4 and results in considerably higher horizontal velocity values. An internal software exception was caused during execution of a data conversion from 64-bit floating point to 16-bit signed integer value. The floating point number which was converted had a value greater than what could be represented by a 16-bit signed integer. This resulted in the operand error, causing the on-board computer to send diagnostic data instead of real flight data. This diagnostic data commanded sudden nozzle deflections and induced a high angle of attack. (for more detailed information, see Report paper Ariane5)

Solution
A simulation of the whole trajectory (static code analysis) should have pointed out the overflow error immediately. This step should have been performed at the stage of architectural design or implementation (prototyping) within the design process.

Lesson
This example illustrates the dramatic consequences of a data overflow software failure, whereby the onboard computer only received diagnostic information instead of realistic flight data. Although there was a back-up system of the failing part apparent in the Ariane5, failure could not be prevented because the backup system used the same software code. Some lessons came forward after the disaster with flight 501 happened:

See the -25 for another failure due to reusing software.
 * Prepare a test facility including as much real equipment as technically feasible, inject realistic input data, and perform complete and closed-loop testing of the total system: Although a (software) subsystem worked perfectly on a previous embedded control system, it can still fail as a subsystem in a new embedded system, i.e.: Always question the reusability of a subsystem. In this case software failed on the Ariane5 whereas it worked very well on the previous Ariane4 rocket! After the accident, a static code analysis painfully showed the overflow.
 * A sensor has to return reliable data in all circumstances: In this case, the IRS (Inertial Reference System) returned diagnostic data instead of real flight data because of a data overflow of a 16 bit signed integer value. In some cases it should be better that the sensor returns nothing at all (or just a warning sign) instead of unreliable data.
 * The high risks associated with complex computing systems took the attention of the general public, politicians, and executives, resulting in increased support for research on ensuring the reliability of safety-critical systems. The subsequent automated analysis of the Ariane code was the first example of large-scale static code analysis by abstract interpretation.

Note: ''In practice there should always be a trade off between safety, economic, (environmental) ,... aspects. For example: In the above example the sensor is a critical component to safely put the astronauts back on the planet, whereas a sensor as part of a conveyer belt system is much less life-threatening. Typically, safety is of most priority at the aviation, aerospace and nuclear sector!''

The Space Shuttle Challenger
On his 10th flight into space, the Space shuttle Challenger disintegrated 73 seconds after take off. 7 astronauts died. The cause of this failure was not only mechanical but also psychological, the so called groupthink!

Problem
Officials of the NASA team decided to launch the spacecraft while ignoring admonitions of the engineers with a sense of invulnerability, given the successful history of NASA. The team worked closely together for a long time and they were under intense pressure to launch the shuttle without further delay that they all collectively went  along with the launch decision. Engineers however knew that the rubber sealing (an O-ring) of the propellant rocket wasn't functioning optimal under freezing temperatures. The cold temperature on the 28th January 1986, causing a leakage of heat flow along the O-ring therefore was the avoidable origin of the death of 7 human beings.

Lesson
This example shows a hardware failure mode: the effect of temperature on the deformation of material. All components of a system can work perfectly together in most of the cases, but fail in bad environmental conditions, such as the freezing conditions in this case. An other important conclusion comes forward. A bad design isn't always the only cause of failures. Also psychological aspects matters. This is where the engineer has to be critical in all circumstances and not collapse under peer pressure. Especially at the stage of usage of an embedded control system, operators have to check whether the environmental conditions fall within the design characteristics before starting up the system. Failures because of such psychological aspects are often hard to overcome and can be seen as an operational failure cause.

Corrosion disasters
Corrosion is often a hard to fight hardware failure mode. Many times disasters happen when materials collapse because of corrosion. Two of them are given below:

Erika was the name of a tanker built in 1975 and sank 70 km from the coast of France on December 13, 1999. Tons of heavy fuel oil ended up in middle of the sea, causing one of the greatest environmental disasters in the world. The economic consequences of the incident have been dramatically felt across the region: a drop in the income from tourism, loss of income from fishing, and a ban on the trade of sea products including oysters and crabs have added to the discomfort.
 * Sinking of the Erika:

Corrosion problems had been apparent on the Erika since at least 1994. In addition, there were numerous deficiencies in her firefighting and inert gas systems, causing explosion risks. Lloyd's List reported that severe corrosion had been discovered just weeks before the incident. However, no immediate remedial action had been taken.

On 28 April 1988, the Aloha Boeing 737 aircraft serving the flight suffered extensive damage after an explosive decompression in flight, but was able to land safely at Kahului Airport on Maui. One hostess was the sole fatality as she was blown out of the airplane, while another 65 passengers and crew were injured. In the aircraft, evidence was found of multiple site fatigue damage leading to structural failure. The National Transportation Safety Board investigation report issued in 1989 attributed the incident to the failure of the operators maintenance program to detect corrosion damage. Because older airplanes are commonly not destroyed and will probably end up in service with another operator, safety issues regarding aging aircraft need to be well understood by the engineer and safety programs need to be applied on a consistent basis.
 * The Aloha incident:

Lesson
Aging effects and corrosion of materials are not visible while the product is in test phase but have to be considered unavoidably! While designing large embedded control systems, engineers should have a long term vision and therefore look at the different Points Of View in the design process of the company. Services, maintenance and testing after sale can be solutions for large embedded systems and can prevent the company from a bad name at long term.

Case Study: The Therac-25
The Therac-25 was a computer-controlled radiation therapy machine, which severely overdosed six people between 1985 and 1987. Three of them died. A case study of the Therac-25 will reveal following design difficulties: In this case the mistake was made of reusing and trusting old software. This is typically a mistake made in high-level design.
 * Software can fail
 * Testing can be difficult, but is indispensable
 * Reuse of software can be dangerous
 * Safety and usability are conflicting design criteria

This text will first discuss the background of the machine. In a following section some relevant accidents are described. Next, the text will focus on some software issues related to the accidents. In a final section some engineering lessons that can be learned from the accidents will be discussed.

Background
The Therac-25, produced by Atomic Energy of Canada Limited (AECL) and CGR, was a medical linear accelerator. Such accelerators produce high-energy beams in order to destroy tumors with minimal impact on the surrounding healthy tissue. The Therac-6, capable of producing X-rays only, and the Therac-20, a dual-mode (X-rays or electron beams) accelerator, were predecessors to the Therac-25. Both machines were versions of older CGR machines, which already had a history of clinical use, augmented with a minicomputer. They both had limited software functionality: the computer merely added convenience to the existing hardware. Hardware safety features from older machines were retained.

A few years later, AECL developed a new acceleration concept (“double pass”) which required less space, was easier to use and more economical to produce. This concept was used in the Therac-25 dual-mode linear accelerator.

In each mode (electron or X-ray), the necessary tools to create the proper beam were attached to the turntable, which rotated the equipment into the beam. Correct operation of the Therac-25 thus was dependent on the position of the turntable. In the case of the X-ray mode, a beam flattener, mounted to the turntable, was used to create a uniform treatment field. In order to produce an output comparable with the electron mode output, this required a high input dose rate. A wrong position of the turntable lead to the wrong position of the flattener and resulted in a high output dose. Obviously, this is a grave hazard when using dual-mode machines.

Although the Therac-25 was controlled by the same computer as the Therac-6 and Therac-20, there were some differences. The hardware of the Therac-6 and Therac-20 was capable of standing alone (for instance, mechanical interlocks which ensured safe operation). However, the software of the Therac-25 had more responsibility for maintaining safety: the machine relied much more on the software instead of hardware safety mechanisms. For the software design of the Therac-25, design features and modules of the Therac-6 were reused. The software also contained some Therac-20 routines.

In the Therac-25, it was the software’s task to control and check the turntable’s position. The software was not flawless though as six people received a massive overdose. This is explained more in the section Accidents.

When the software detected an error the machine could shut down in two ways:

When a 'treatment pause' occurred, the operator merely had to push the P-button to "proceed" and resume treatment without having to reenter treatment data. When this feature was called five times the machine would automatically suspend treatment.
 * Treatment suspend: which required a machine reset to restart
 * Treatment pause: which required a single key command to restart the machine.

Accidents
July 1985, Ontario (Canada)

About five seconds after activation of the Therac-25, the machine shut down. It indicated a 'treatment pause' and that no dose was given. The operator tried a second attempt at treatment by pushing the "P-button", but the machine kept shutting down four more times until it went into 'treatment suspend'. After the treatment, the patient complained of a burning sensation to the treatment area. In reality the patient was given a large overdose, approximately 100 times the intended dose. Normal single therapeutic doses are about 200 rads. Doses of 1000 rads can even be fatal, if delivered to the whole body.

After investigation of this accident AECL found some weaknesses and mechanical problems, but could not reproduce the malfunction that occurred. AECL then redesigned some mechanisms and altered the software to tackle these problem. After these improvements AECL claimed that "analysis of the hazard rate of the new solution indicates an improvement over the old system by at least five orders of magnitude". The hazard analysis, however, did not seem to include computer failure. Thus, more accidents occurred.

March 1986, East Texas Cancer Center (ETCC)

The operator had lots of experience with the machine and could quickly enter prescription data. She wanted to type "e" (for electron mode), but she had pressed the "x"-button (for X-ray) by mistake. To correct this, she used the "up-key" and quickly changed the mode entry. The other treatment parameters remained. To start treatment she hit the "B-key" (beam on). After a moment the machine shut down and showed the error message: "MALFUNCTION 54", which was not explained nor mentioned in the machine's manual. The machine went into ‘treatment pause’ which indicated a problem of low priority. The machine showed an underdose, so the operator hit the "P-button" to proceed treatment. Again the machine shut down with a MALFUNCTION 54 error. The patient complained he had felt something like an electric shock and was immediately examined. The physician however suspected nothing serious. In reality the patient received an immense overdose. Real doses of 16500 to 25000 rads were estimated after the facts. Five months later, the patient died from complications of the overdose.

April 1986, East Texas Cancer Center (ETCC)

Three weeks after the first accident at ETCC, a similar one occurred. The same operator noticed an error in the mode and used the "up-key" to correct it. Again the machine showed a MALFUNCTION 54 error. This patient died from overdose three weeks after the accident. The ETTC physicist immediately took the machine out of service after this second accident and investigated the error on his own. The operator who remembered what she had done, worked with him. With much effort they were able to reproduce the MALFUNCTION 54 error. The key factor in reproducing this error was the speed of entering data: if the data were entered quickly the error occurred.

The same computer bug was present in the Therac-20. But because the Therac-20 had independent hardware protective circuits, this problem was just a nuisance.

Problem
Just a small part of the software will be studied, yet this can demonstrate the overall design flaws.

The two basic mistakes involved in the accidents are:
 * poor software engineering practices
 * building a machine that relies on software for safe operation

Race conditions as a result of the implementation of multitasking are possible. Following reasons state why: These race conditions played an important role in the accidents.
 * Concurrent access to shared memory is allowed
 * Aside from data stored in shared variables, there is no real synchronization
 * The "test" and "set" for shared variables can’t be divided into two single operations.

Software bugs for ETCC accidents

Figure 1 illustrates the treatment process. The treatment monitor (Treat) controls the eight treatment operation phases or subroutines according to the value of the Tphase variable. The subroutine Datent (data entry) and the Keyboard Handler task use a shared variable (data entry complete flag) to communicate with each other. Once the data entry is complete, the Keyboard Handler task changes the value of this shared variable, which denotes Datent to change the value of Tphase. The Datent subroutine exits back to Treat, which will reschedule itself in order to start the following subroutine.

Another shared variable, MEOS, contains the mode and energy level specified by the operator. MEOS exists of 2 bytes: a low-order byte to set the turntable and a high-order byte, used by Datent, to set several operating parameters.

The operator is forced to enter mode and energy level by the data entry process but he can edit the data later. A problem can occur when the operator changes the data in MEOS after the ‘data entry complete’ flag has been set by the Keyboard Handler task. Datent is then already exited and thus won’t detect the changes. However, the turntable is set in accordance to the low-order byte of MEOS and can therefore be inconsistent with the information in the high-order byte. This inconsistency apparently can’t be detected by the software.

After Datent finished setting the operational parameters, via the high-order byte information, it calls the subroutine Magnet, which sets the bending magnets of the turntable. Following pseudocode shows relevant parts of the software (taken from the paper of Nancy Leveson, p. 27):

Datent if mode/energy specified then begin calculate table index repeat fetch parameter output parameter point to next parameter until all parameters set call Magnet if mode/energy changed then return <b style="color:blue">end</b> <b style="color:blue">if</b> data entry is complete <b style="color:blue">then</b> set Tphase to 3 <b style="color:blue">if</b> data is not complete <b style="color:blue">then</b> <b style="color:blue">if</b> reset commando entered <b style="color:blue">then</b> set Tphase to 0 <b style="color:blue">return</b> Magnet Set bending magnet flag <b style="color:blue">repeat</b> Set next magnet <b style="color:blue">call</b> Ptime <b style="color:blue">if</b> mode/energy has changed <b style="color:blue">then</b> exit <b style="color:blue">until</b> hysteresis delay has expired Clear bending magnet flag <b style="color:blue">return</b> Ptime <b style="color:blue">repeat</b> <b style="color:blue">if</b> bending magnet flag is set <b style="color:blue">then</b> <b style="color:blue">if</b> editing taking place <b style="color:blue">then</b> <b style="color:blue">if</b> mode/energy has changed <b style="color:blue">then</b> exit <b style="color:blue">until</b> hysteresis delay has expired Clear bending magnet flag <b style="color:blue">return</b>

It takes about 8 seconds to set the magnets. The subroutine Ptime is used to introduce this delay. Ptime is entered several times, because several magnets have to be set. To indicate the bending magnets are being set, a flag is initialized when Magnet is entered. This flag is cleared at the end of Ptime. When an editing request is submitted, the keyboard handler sets a shared variable which is checked by Ptime. If edits are present, Ptime will exit to Magnet, which then exits to Datent. However, this shared variable is only checked when the bending magnet flag is set. But this flag is cleared after the first execution of Ptime. So any edits performed after the first pass through Ptime will not be noticed! In the ETTC accidents the error occurred, since the edits were made within 8 seconds. Hence Datent never detected the changes. This problem was partially solved by clearing the bending magnet flag when all magnets are set (at the end of Magnet).

Lesson
Some lessons can be learned from these accidents.

 * Do not ignore or overrely on software Engineers may not assume a problem is caused by hardware. Extensive testing and safety analyses at software level is necessary, not on system level alone. Every safety-critical system should have incident analysis procedures that are applied whenever a problem is about to occur that might lead to an accident.

 * Be careful reusing software The reuse of software does not imply safety because it already has been exercised extensively. Revising and even rewriting the entire software may be safer in many cases, because every new development will introduce its own (new) errors.

 * Design for the worst case It is crucial that an error is detected and indicated properly (towards the operator) in order to take the right steps. A way to obtain correct information about the errors is by designing error detecting code into the software from the beginning. Self-checks, error-detection and error-handling features must be given high priority in making tradeoff decisions.


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Talk:A-level Mathematics/OCR/C2/Circles and Angles

I have changed 15° on the radians example to 20° as this makes the answer 1/9π rad

I also think that on the arc length example the answer should become 5.550147021cm = 5.55cm as 33.3...cm is quite large for a circle with only a 6cm radius and 53° angle. I will change this to the answer that I think is correct unless someone else disagrees.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text: User talk:70.225.75.211

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User:Veenabose

Hello am chandra bose from india. Windows Guru

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User talk:Aphonik~enwikibooks

Welcome to Wikibooks, Aphonik! – Mike.lifeguard  | talk 21:11, 7 April 2008 (UTC)

Your account will be renamed
Hello,

The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.

Unfortunately, your account clashes with another account also called Aphonik. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Aphonik~enwikibooks that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.

Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.

Sorry for the inconvenience.

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text: User talk:65.92.175.70

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PsycholARTSical: Psyched about the arts/Personal Development: Classroom Community + Character Development

Personal Development: Classroom Community and Character Development - The Tribes Program - (Kate R, Ayanda, Jeff M, Natalie, Laura B, Jamie T)

Thesis
The education system today is evolving beyond traditional teaching methods. Presently, educators are becoming more aware of the significant role that schooling plays in the personal and social development of students. The atmosphere of a classroom has the ability to contribute to or detract from a student’s development and opportunity to learn. Successful students will emerge from positive learning environments that promote community development, cooperative learning, and character education. The Tribes program focuses on implementing these characteristics into every school in order to ensure that all students succeed. The Tribes program is a process of establishing a positive culture of learning and human development throughout an entire school community. Tribes began in the early nineteen seventies in response to the concern that educators and parents were having over low test scores and a rise of school behavioural problems. Jeanne Gibbs, the former Executive Director of the Centre for Human Development and co-creator of the Tribes process, piloted a group development process that would fundamentally change the atmosphere of schools. Gibbs believed in the good of all students and argued that it was the systems that surrounded the students that impacted their lives and needed to be the focus of change (Gibbs, 1995, p.399). The pilot program was a success and led to the creation of Tribes. The overall goal of Tribes is, “to engage all teachers, administrators, students, and families in working together as a learning community that is dedicated to caring and support, active participation and positive expectations for all students (Gibbs, 1995, p.22).” Tribes is an effective and practical program that all teachers have the ability to implement in their classrooms. The program is appropriate for all levels of the school system and can be successfully implemented in the music, drama, and arts classroom. Tribes ensures that all student receive a complete personal and social education.

Community Development
The Tribes program involves the creation of long-term learning groups in the classroom. However, before the class is ready to build their tribes, it is important that the whole class is an inclusive environment. The first several weeks of a school term should be used to build community in the classroom and to establish a positive social climate. Students should engage in activities where they are able to get to know each other, learn the important norms in the classroom, and become comfortable in the environment. The teacher should encourage participation and help students become comfortable with group sharing. The teacher must also demonstrate what their role is in the classroom. In the Tribes model the teacher is there to guide the students in their learning process. The role of the teacher is to present the subject to students, challenge them to work cooperatively through the information, and be there to give support and answer questions (Gibbs, 1987, p.36). The teacher must therefore establish effective communication with the students. This is a necessary component to the development of a positive teacher student relationship (Woolfolk, p.427). This period of community building is essential to the success of the Tribes model.

Throughout the community building period it is important to develop guidelines for what students need to do in order to feel they are in a trusting group. The Tribes program has created four basic tribal norms for all classrooms to abide by. The first norm is Attentive Listening. Students should learn how to pay close attention to the words and feelings of their classmates. Respect and care should always be a part of attentive listening. The second norm is No Put-Downs/Appreciation (Gibbs, 1987, p.21). The Tribes program believes in the importance of nurturing students’ self-esteem, and the discouragement of negative remarks is a key component to the increase of self-esteem (Woolfolk, p.71). Encouraging students to value each other and state the appreciation of other’s unique qualities is another important part of helping students to feel self-confident. The Right to Pass is the third tribal norm. This norm means that students have the right to determine to what extent they will participate in group activities. This norm helps to develop a safe space in the classroom because students are aware that they have a right to privacy. Students also see that they are able to take responsibility over their own well-being and through this process students will develop the courage to become more open with their peers. The last tribal norm is Confidentiality. Students are assured that all sharing that is done within the classroom is honoured and will not be revealed. It does not mean that students cannot share what they did in class, but rather that gossiping is forbidden (Gibbs, 1987, p.40-41). Each of these tribal norms has equal value in the classroom and should be observed at all times. Teachers should encourage the class to help each other stay true to the norms so that the students are also responsible for the creation of a whole class community.

Cooperative Learning
Once the teacher feels that the class has created a positive and inclusive environment the students are ready to create their long-term learning groups. In order for the groups to be successful the teacher must balance the members sociometrically. The teacher must assign an age appropriate number to each tribe. For elementary and middle school students there should be groups of four and five. For high school and adult classes groups of five and six are appropriate. The number of male and female students in each learning group should also be balanced. Leaders in the class should be distributed among all the tribes. Students who are of high and low peer acceptance should also be distributed evenly among the tribes. Once the composition of the tribes has been determined the teacher should create an exciting activity for students to find their tribe (Gibbs, 1987, p.51). The process of building tribal cohesion should then begin. Each group should go through the process of inclusion, influence, and affection. These stages involve the students building trust within the group, creating an atmosphere of support and care, and discovering their value within the group. This process ensures that groups become unified and will be able to act as a true cooperative learning group (Gibbs, 1987, p.24). The purpose of the tribes is to not only create social connections among students, but to allow students to engage in cooperative learning. Cooperative learning allows students to work together to maximize each other’s learning. In a tribe, students share personal concerns and feelings with each other, as well as plan, problem-solve, discuss, and complete work from the curriculum. Cooperative learning is beneficial for students because it has positive effects on their personal and social development, as well as their learning process. For example, studies have found that cooperative groups can help increase students’ empathy, tolerance, and friendships (Solomon et all., Woolfolk, p.333) In addition, it has been discovered that cooperative work can help students with their information processing. Through discussions students are better able to organize and expand their knowledge, make connections and review material. Cooperative work also encourages students to think critically and problem-solve in a group situation (Woolfolk, p.333). In order for cooperative learning to be successful the groups need to maintain an atmosphere of positive support for all members. Groups must also assume responsibility for themselves and their achievement of goals. The teacher should never participate directly in the group, but should always maintain control and intervene if the social cohesion of a group breaks down. The Tribes program is an effective way to create an environment for successful cooperative learning. The tribes become support systems for the students and create a positive space for learning (Gibbs, 1995, 49).

Character Development
The overall mission for Tribes is, “to assure the healthy and whole development of every child so that each has the knowledge, skills, and resiliency to be successful in a rapidly changing world (Gibbs, 1995, p.22).” Essentially, the mission of tribes is to help students with their character development so that they can make a positive influence in society. Throughout the entire process of tribes character development is a main component. Character education is embedded in the Tribes program without it being lessons based on specific values. The process of working in groups, for example, encourages helpful behaviour in students, it promotes inclusion and the celebration of diversity. Students are encouraged to express their views as well as respect different points of view. In groups, students also learn to establish trust among members, and through group work they become kind and caring individuals. In addition to social values students also develop their self-actualization. Students are encouraged to build their personal identification, and their skills, talents, and gifts are identified and valued by the whole class. Students are also encouraged to develop self-respect and resiliency so that they can be socially responsible both in the classroom and in society (Gibbs, 1987, p.69-70). Overall, the Tribes program is a beneficial process for students to participate in because it helps students to better develop their whole selves.

From Theory to Practice
The Tribes program has numerous connections to a number of the concepts outlined and discussed in the textbook.

Motivation

The Tribes program fosters both intrinsic and extrinsic motivation in several ways. Tribes places emphasis on the acquisition of knowledge and skills that will serve students throughout their lives. For this reason, the Tribes program is applicable and valuable to students – in and out of school – and many may be intrinsically motivated to participate and develop as individuals. The group dynamic around which Tribes is centered also contributes to students’ extrinsic motivation in a number of capacities. For one thing, students’ may experience an increased desire to participate in activities that are community, or group, based. Students often appreciate the opportunity for increased interaction and collaboration among peers. Tribes requires participants to provide each other with positive feedback and reinforcing statements of support which can be a powerful motivating factor. Additionally, students may mimic the positive behaviour of others in their Tribes group(s). Tribes has the potential to help students develop as more self-regulating and responsible individuals. Because students are extremely involved in the learning process, they have great control over their own learning and actions in general.

Self Concept

Tribes can have a powerful impact on students’ positive perception of themselves. The appreciation statements students are required to make about one another may help individuals to recognize their particular strengths and talents. Tribes also offers students the opportunity to work in groups and be independent with regard to their own learning and behaviour, all of which may lead to increased self confidence in their abilities, as well as increased self-worth. The four sources of self-efficacy (listed below) outlined in the textbook relate closely to this aspect of student development. 1.	Mastery experiences 2.	Level of arousal 3.	Vicarious experiences 4.	Social persuasion When a student’s self-efficacy is healthy and well developed, he/she will put forward greater effort. Additionally, increased self-efficacy also effects the student’s ability to set goals for him/herself and directly connects to his/her motivation with regard to a particular task or tasks. This co-operative goal structure can support and enhance students’ motivation within a community-based setting.

Potential problem: While the group dynamic supports both intrinsic and extrinsic motivation, it may also affect some students in a negative way. Students may feel increased pressure or anxiety to contribute to the group, while others may refrain from participating at all for fear of humiliation.

Behavioural Views of Learning

The positive/affirming statements involved in the Tribes program act as reinforcers – they strengthen or maintain the students’ positive behaviour and/or response(s). One of the great things about Tribes is that is does not involve or condone punishers/punishment. In fact, the program goes out of its way to ensure that this negative reinforcement does not take place – for example, all participants are enabled with the ‘right to pass’ on any given activity, without negative consequences or repercussions of any kind.

Potential problem: One of the possible problems with the group/community approach is that, while all opinions are respected and all participants are expected to be positive and contributing group members, there may be individuals who are not satisfied with a particular group decision.

Classroom Management: Establishing goals

One of the ways in which Tribes positively impacts the positive environment is through increased student engagement. For reasons previously outlined, the Tribes program supports both intrinsic and extrinsic motivation for students. Increased motivation will lead to increased engagement in the classroom activities and environment and thus students will have the opportunity to participate in and produce quality, meaningful experiences. Additionally, as mentioned above, Tribes helps students developed greater self-management, self-control and responsibility, all of which are extremely valuable with regard to ease of classroom management. The 4 Agreements of Tribes communities: 1.	Attentive listening 2.	Appreciation/no put downs 3.	Right to participate/pass 4.	Mutual respect The clearly established rules and procedures of Tribes also help to establish a positive classroom environment and decrease issues related to classroom management. These four agreements, in particular, are designed to foster cooperation among students as well as self-acceptance.

Classroom Management: Prevention

Kounin identifies a number of factors that help to prevent classroom management problems: 1.	Teachers must take student differences into account 2.	Teachers must maintain student motivation 3.	Teachers must reinforce positive behaviour. Kounin goes on to state that individuals who are skilled at preventing classroom management issues all have four areas of skill: 1.	“Withitness” 2.	Overlapping 3.	Group focussing 4.	Movement management

The connection between Kounin’s ideas and the Tribes program are highly evident and, additionally, Tribes builds on these concepts by expanding the ‘preventer’ to include students as well as teachers. Because Tribes places great importance on student-directed learning, activities and environment, the students are all actively involved in contributing to the atmosphere of the classroom and directly connected to the classroom management problems (or lack thereof).

Learning Environment: Establishing Community

Johnson and Johnson outline ‘three Cs’ of establishing a positive classroom community: 1.	Cooperative community 2.	Constructive conflict resolution 3.	Civic values

These principles are essentially the basis for the Tribes program. Johnson and Johnson identify ‘positive independence’ as individuals working together to achieve mutual goals. This concept is a crucial part of Tribes – connecting to student self-direction, motivation as well as cooperation and affirmation. Constructive conflict resolution is another important part of Tribes – seen in students’ right to pass as well as the ban on put-downs. Additionally, Tribes supports the ‘I feel’ method of communication between students – particularly those in conflict with one another – and helps students to understand the emotion behind actions and behaviour, rather than allowing an aggressive action/behaviour to proceed with no understanding on the part of the aggressor or the recipient. Finally, because Tribes also aims to foster students’ character development, the idea of ‘civic values’ is also extremely applicable. According to Kounin, students come to understand values through direct teaching, modelling, literature, group discussions and the sharing of concerns. Again, Tribes takes this a step further by assigning these duties to, in addition to the teacher, the students themselves.

Structuring a Tribes Lesson Plan
Tribes lesson plans are generally structured to include 5 distinct steps:

1.	Energizer

2.	Circle Talk

3.	Learning Activity

4.	Reflection

5.	Appreciation

Each step addresses at least one of the “Five E’s”:

1. Engage

2. Explore

3. Explain

4. Elaborate

5. Evaluate

Step One: Energizer (Engage)

The purpose of the energizer is to serve as a warm-up and transition. The energizer should prepare students physically and mentally for the upcoming learning experience in a fun and engaging manner.

Step Two: Circle Talk (Engage, Explain, Explore)

The circle talk is a way for students to become more familiar with themselves – their strengths, abilities, gifts, etc. in relation to the upcoming learning experience. It is important that during the circle talk all students adhere to the four “community agreements” of the Tribes program. This includes listening attentively while others speak, showing respect for the feelings and ideas of others, avoiding put-downs and showing appreciation, and honouring each others’ right to pass.

It is up to the individual teacher to ensure that the circle talk is effective. Some suggestions include:

- Remember that this is a time for everyone to speak – not just the teacher

- Allow at least 3 second of thinking time after asking a question

- Consider your students and decide what method of taking turns will work best. Can the group handle speaking out randomly whenever they have something to contribute, or do they need more structure, such as using a ‘talking stone’?

Step Three: Learning Activity (Engage, Explain, Explore, Elaborate)

Learning activities should help students to connect the new information being presented to prior knowledge and experiences. A good way to do this is by starting the activity with personal YOU questions. Examples of YOU questions include:

- How do you feel about the subject?

- What experience do you have with this subject?

When students are responding to these questions, it is best for them to be in groups of no more than four. This allows every student a chance to speak, and is less intimidating than sharing personal thoughts and experiences with the entire class.

The learning activity should require cooperative interdependence from students, so that every student is an important and necessary part of the process. A great way to ensure cooperative interdependence is by having each member of each group take on a specific role. Examples of roles include:

-	Facilitator

-	Recorder

-	Encourager

-	Summarizer

-	Time Keeper

-	Materials Manager

NOTE: It is important that students do not take on the same role every time – all students must have practice fulfilling each role.

Step Four: Reflection (Engage, Explain, Explore, Elaborate, Evaluate)

Reflection is an important step in any learning process. Research has shown that reflection can significantly increase the amount of information and number of concepts students retain. There are three types of reflection questions:

1.	Personal Learning Questions (about what the student has learned or felt)

2.	Social Questions (about the interactions between group members during the learning activities, and what collaborative skills were used)

3.	Thinking Questions (about the actual content of the lesson, and what skills were required to understand and work with the information and concepts)

NOTE: It is not necessary for students to always answer the reflection questions out loud. Students should be allowed the option of simply thinking about their answer, or of writing it down.

Step Five: Appreciations (Engage, Explore, Evaluate)

This step is a great way for students to develop a sense of community and trust with one another. Students can express appreciation for the efforts and accomplishments of the other members of their group, and can point out each other’s strengths and skills. This step is especially important for high school students, who greatly value the opinions of their peers. High school students often find praise or acknowledgement from a peer to be more meaningful than praise or acknowledgment from a teacher.

Sample Tribes Lesson Plan
This is a sample of a lesson plan that could be used on one of the first few days of a semester to introduce the Tribes program and help students develop a trusting and collaborative atmosphere in the classroom.

Energizer: Three Ball Pass (5 – 7 min.)

This game helps students learn and remember each other’s names. It also requires them to work collaboratively as a team.

Start with the students standing in a circle. The leader will begin the game by calling out the name of a student and tossing the ball to him/her. That student will then call out another student’s name and toss the ball to him/her. This will continue until every student has been tossed the ball, with no repetitions.

The students should then repeat the same pattern of tossing, trying to increase their speed. Once they have accomplished this pattern once or twice, a second ball can be added. The second ball should be tossed in the same pattern as the first. Once a ball has reached the end of the pattern, it should start all over again, so that the two balls are constantly in motion. A third ball should then be added.

To increase the challenge of the game, any of the following strategies can be used:

-	The second ball can be thrown in the reverse pattern of the first

-	Each ball can be given its own pattern

-	The group can time themselves and try to beat their own best speed

Circle Talk: Elements of a Positive Classroom (10 – 15 min.)

Discuss what elements help to create a positive classroom environment. Students can suggest what they would like to see/feel in the class, and things they would like to avoid. Students can share examples of situations and environments that have been positive and why, and ways they personally can contribute to a positive classroom.

Learning Activity: Brainstorming the 4 Agreements (15 – 20 min.)

Split the class into 4 groups. Each group will start at one of the four flip-charts that have been set up around the room. Each flip chart will have one of the Tribes Agreements written at the top:

1.	Mutual Respect

2.	Attentive Listening

3.	Showing Appreciation/ No Put-downs

4.	The Right to Pass

Explain to students that this is a brainstorming activity, and that there are no right or wrong answers. Explain that the idea is to write down or sketch thoughts, ideas, feelings or images that come to mind when they consider the words on the flip-chart. Remind them that they should work quickly, without commenting or discussing.

Give the groups 3-4 minutes at the first flip-chart to record their immediate reactions. Once the time is up, have them rotate around to the next flip-chart. Each group should spend 3-4 minutes at each flip-chart, rotating through until they have worked at all four stations.

Reflection: Reflecting on the 4 Agreements (5 – 10 min.)

Post the charts up where everyone can see them, and have the students sit facing them. Pose the following questions to students:

Personal Learning:

-	How do you feel about each of these agreements?

-	Which agreement do you personally think is most important and why?

Social Learning:

-	What would have happened differently during this activity if we had judged, commented or discussed the ideas instead of simply writing them down?

-	How much did you personally participate?

Cognitive Learning:

- Did you learn anything new about these concepts and their importance?

Appreciations: Appreciating the Members of Your Group (5 – 10 min.)

Invite students to share statements of appreciation, or recognition for others in their group. Because this is the first time the class has done this, you can suggest that they start their statements in any of the following ways:

-	I like it when …

-	Thanks (name) for …

-	I thought (name) did a really good job at …

Tribes in Action: The Secondary Dramatic Arts Classroom
After a basic introduction to the Tribes program it is clear that there are four agreements required to initiate the tribes program into a school or a classroom are attentive listening, appreciation/no put-downs, right top participate/pass and mutual respect. It is also clear that there are three stages of group development, beginning with inclusion, building through influence and ultimately creating a community. If Tribes is a medium through which a community can in fact be created, one must understand what a community in a drama classroom might look like.

A Community in a High School Drama Classroom

It is especially important for students in a dramatic arts classroom to feel safe since many of the techniques and issues raised, as well as the collaborative nature of drama projects require students to stretch their comfort limits and take risks. Building a community among the students is an essential part of a functional and productive drama classroom. Since drama involves taking risks, it is appropriate to look at strategies of creating communities for high risk students. In their case study, “Serving Rural Youth at Risk: A Portrait of Collaboration and Community,” Robert Rossi, Pamela Vergun and Larry Weise describe eight commitments that students must share in a community: a shared vision and shared values, a sense of purpose, an incorporation of diversity, open communication, active participation, caring and trust, teamwork, respect and recognition.* Although this case study is focused on serving rural youth at risk, all eight of the aforementioned commitments are also essential in a drama classroom. Consider the production of a play; a diverse group of students, with a diverse mix of skills and interests, share a vision of performance in which every person plays a respected and recognized role whether that be as an actor, technician, designer, musician or writer. As the show approaches, everyone must trust the individuals of the group and actively work together.

Inclusion and Influence as Community Builders

Since community building is a necessity in the dramatic arts classroom and the Tribes program describes community as the product of inclusion and influence, then a dramatic arts teacher needs practical strategies to incorporate inclusion and influence in their classroom. The Tribes program breaks these strategies into four categories: active listening, expression of appreciation, reflecting upon experience and collaborative work. Each of these categories involves an essential aspect of the dramatic art form and each can also be cultivated through a variety of exercises that can easily be incorporated into the dramatic arts classroom.

1) Active Listening

Drama inherently requires active listening for acting and improvisation. An actor can not act in a scene without listening to their partner or improvise a scenario without listening to the offers on the table. Try these games to train active listening skills:

Blind Association Circle With the entire group standing in a circle, establish a rhythm, by swinging a hand. Once a rhythm is established, one player starts by tossing a word to their neighbour, who associates on the word and tosses another word. It is important to stay in the rhythm. Tell the players to just say `banana` if they feel they cannot think of a word, as long as the rhythms does not get broken. Once the association has been to each player, continue, repeating the same pattern. As this is  going on, the teacher will tap all players, gently on the shoulder, at tree different times. The first tap: players close their eyes but continue the free association, sticking to the rhythm. The second tap: everyone starts walking around (carefully!), eyes still closed. Players have to  recognize the voice of their ex-neighbour in the circle to know when it is their turn. Third tap: all players, still eyes closed, and still associating, try to reconstruct the circle. Exercise is over when everyone is in a circle again. Trainer should keep an eye on players so they do not walk into anything.

The Paperclip Game Have the players form a line across the back of the playing area. One person steps forward and says what object he/she is and what their function is, such as "I'm a paperclip, and I hold loose  papers together." A second person steps up and says what object he/she is, and what their similar function is, such as "I am a rubber band and I hold loose pieces of mail together." At that point a pattern is established and one-by-one everyone steps forward to heighten the pattern: •	I am twine and I hold loose recyclable newspapers together. •	I am shackles and I hold loose chain gang prisoners together. •	I am religion and I hold loose communities together. Repeat until it is as heightened as it is going to get, then start over again with a new object and function. This game is great to encourage students to actively listen for patterns and heighten what has already been established.

Active listening is also an important skill for audience members to learn and apply. Encourage students to employ proper audience etiquette through active listening. Create checklists or questions for students to answer while viewing each other’s work. Questions could include: •	What particular gestures, lines, or moments stood out as creating a believable character? •	How did the performers relate to one another and when was it clear that they were listening and responding to each other? •	Did the pace or rhythm of the production seem smooth or did it drag? •	How was the meaning of the text communicated through words, actions, or symbols? •	What were the major desires, goals, objectives, and motivations of the characters and how did these help you understand the meaning of the text? •	Were the characters realistic, symbolic, allegorical or totally divorced from reality?

2) Expression of Appreciation

Teachers can build in activities to help students express their appreciation for one another’s work after a specific exercise, at the end of each week or at the conclusion of a unit or production.

End of an Exercise: Oscar Speech Journal Ask each student to write an “Oscar Speech” thanking those who made their success in this activity possible today; who helped you and in what way? Remind students that they can also thank themselves.

End of the Week: Secret Admirers At the beginning of each week, give each student a small card with the name of another student in  the class written on it. (Be sure to keep track of who has been given what names which will help  you minimize repeats and deal with any inappropriate notes.)  Over the course of the week everyone has to watch for one great thing they noticed their person do in class and then record it on the card. On Friday collect the cards then hand everyone their secret admirer note.

End of a Unit: High Fives Give each student a piece paper and instruct them to trace their hand on it. Then they must creatively add their name to the hand. Sitting in a circle, pass the hands around so everyone can write a thank you, complimentary or congratulatory message on each persons hand: a high five.

3) Reflecting upon Experience

Here are a couple of ways to facilitate personal reflection within a group. Either can be done after any significant shared experience such as a production, unit, trip, or exercise.

Spider Webs Have the entire class sit in a circle and give one person a ball of yarn. That person will reflect upon the present experience: something that worked well, something they learned or really enjoyed, something that was memorable, etc. Once they have finished they will wrap the yarn around their wrist a couple of times and then through it across the circle to another person. That person will do the same thing. Once the yarn has been to everyone once or twice, a web will have been created in the middle of the circle. Open a discussion about the nature of a web and how that relates to  our shared experiences here in the drama room.

The Good, The Great and The Goal Tableaux Divide the class into groups of 3 or 4. Each group will decide upon a good part and a great part of the present experience. The group will also think about what their goal or goals might be in  relation to the present experience. Once all three things have been clearly decided upon, the group will create a tableau to illustrate each. The groups will present all three and the class will describe what they saw, opening a group discussion after each presentation.

4) Collaborative Work

The majority of all work in the dramatic arts classroom is collaborative. The curriculum itself is working to build community through inclusion and influence, however, an easy way to introduce the idea of collaborative work is through cooperative games. These types of activities are great for early in the semester and require students to work in order to solve a problem or succeed as a group.

Shrinking Island Divide the class into groups of 6-10 students and give each group a blanket. Ask the students to  stand on their   blanket and then explain that this blanket is a shrinking island. The students must get off their island and make it shrink (fold it in half) now the students must al get back on. Continue shrinking the islands to see which group can work together to stand for five seconds on the smallest island.

Magic Carpet Divide the class into groups of 6-10 students and give each group a blanket. Ask the students to stand on their blanket and then explain that this blanket is a magic carpet. Describe flying through the air and get them to act out their adventure. Now the carpet loses control and is  about to crash. The landing instructions are on the bottom of the carpet, so each group must work together to flip the carpet, while it is in mid air, in order to see the instructions. No one can fall off!

Elements of Tribes that Relate to Visual Arts
There has been an educational movement where teachers and administrators alike where they have become very interested in a program named Tribes. In this part of the paper, two concepts are going to be explained. For the first part the ideas and process of Tribes in relationship to Visual Arts will be explain. Through this explanation, an evaluation and critical ideas are presented in order to figure out away in order to incorporate Tribes in a Visual Arts classroom in a high school setting.

Tribes is a program which was first developed for elementary school but has recently been modified to be able to be incorporated into high schools. It is a step-by-step program which is designed to achieve precise learning goals. In order to achieve these learning goals, there are four agreements which need to be introduced by the teachers and honoured by the students within the whole school. Tribes in Visual Arts, is a process of establishing a positive culture of learning and human development not just within individual classrooms but in an entire school based community. For the program, Tribes wants to assure the healthy and whole development of every child so when they go out into the work force they are able to be knowledgeable, skillful, and determined to be successful.

There four agreements which can be easily incorporated into Visual Arts which are key to Tribes. These four agreements are (1) attentive listening, (2) appreciation/no put downs, (3) mutual respect, and (4) the right to pass. In order to achieve all these elements within the Tribes program students need to learn a variety of skill which will help them to be able to collaborate and work will in long-term groups. These skills include: helping each other to achieve tasks together, set goals and solve problems, monitor and assess progress and celebrating achievements.

When introducing Tribes to your Visual Art classroom, there are a number of things the teacher needs to do in order to make the program successful. The first thing the teacher needs to do is introduce Tribes and explain it to the students in student friendly language. The second thing the teacher needs to do is divide the class into groups which are balanced in terms of student strengths verses student's weaknesses. Thirdly, the teacher needs to establish tools and techniques to help build group inclusion within the individual groups and as a class as a whole. Once the students are in their groups and they have ideas about inclusion the teacher now can start transferring their power over to the students.

In order to implement Tribes into a Visual Art class there needs to be a structure established based off of three things. The first thing is cooperative learning, the second being character education and last of all, community development. Students become members of long-term learning groups. In terms of cooperative learning students would be divided into groups. For junior grades the groups would consist of 4 to 5 members and in high school the groups would consist of 5 to 6 members. For character development students incorporate their values into the everyday life in the classroom and they also learn essential collaborative skills. Last of all, for community development students need to feel like they are part of a caring and safe classroom environment.

As mentioned above, for Tribes to work to the fullest extent, it has to be implemented in all classrooms. This part of the paper will examine one possible way in order to implement it into a visual art classroom through a mural project.

Visual Arts Mural Project and Tribes
In visual arts students develop many skills which can be directly linked to the ideas of Tribes. Visual arts, developed respect for other opinions and feelings without being judgmental, promote cooperative learning where students develop problem solving skills, create a caring and trustworthy environment where students feel they can express themselves freely and last of all, the appreciation of cultural values. All these elements that are developed in a visual art classroom help students socially develop so they will be able to be active citizens within a community. It also helps student to be able to cooperate and work well together in large group in order to successfully create a class mural.

When starting a class mural project in a visual art classroom, a community must be build just like in Tribes classroom community must be created. When building a community, make sure students understand that the activity is a group activity and they will have to work with everybody in the class. This might be a hard thing to do in a visual art classroom because for many visual art project students work alone reflecting and thinking about their art. Many students might be reluctant to have to work and create art with their fellow classmates when they are generally used to working alone on their art. Students need to understand that many project that artist work on in today's world are done collaboratively. To prove this point you might want to show students examples of work done by a group of artist. Overall, students need to understand that large scale murals are done by groups of people.

Once the students understand that they will have to work in group to create the class mural, the teacher can start and activity where the class brainstorms possible ideas for the mural. It is really important to be inclusive and make sure all the students understand that every body's ideas are important. This concept in Tribes is also important. One issue that might develop with the students is decided on one idea when you might have several. One way to solve this issue is to create lists where students would vote of the ideas presented.

Keeping with the ideas of Tribes students need to influence the look of the mural. In order to do this the teacher can create design projects to give students the power to influence to look and ideas behind the mural. What students can do is create their own drawings on how they wish the mural to look. Once the drawings are finished, have all the drawings posted around the class and develop a classroom discussion on which images they want to use for the mural. Remember when having such a discussion it is important that students are nice and not mean and degrading towards their classmate's image. To avoid negativity you might want to create an answer sheet for the murals so when the student talks they are using their sheets as a reminder of what they want to say. Once decided on the design of the mural divide the mural up so every student gets an equal amount of the mural to create as their own.

There are many things that teachers need to keep in mind when creating Tribes in their classroom particularly in terms of a large scale mural project. Teachers have to make sure their instructions are clear and that every student in their class understands them. Secondly, in order to make the project run smoothly teachers need to create a time schedule and emphasise how important it is to following it. Overall, when creating such a large collaborative piece or any visual arts project it is really important for the teacher to keep the students engaged. Also, when creating a mural or class project of this scale it’s a great opportunity for teachers to get the parents involved in a school art exhibition.