AUSENTISMO SEGUIMIENTO

All interactions (joint actions) with people are set in the context of their surroundings. Context provides a wealth of information so that, for example, in a conversation people can get directly to the purpose of the discussion without much additional explanation. The starting point for a discussion is based on the context of the participants and their situation.

Common ground refers to the contextual information that participants of the joint action continue to have for an understandable exchange. Common ground is the

contextual information all participants interpret similarly. Otherwise, there is confusion when one person makes a reference to something that another person has interpreted differently.

Another perspective on common ground is that it deals with the self-awareness of the participants. A participant must have a self-awareness of his surrounding context and awareness of how other people will interpret that context.

To illustrate common ground, consider the earlier joint action in the grocery store. Before Alberta and Benjamin even start conversing, they have a common ground about each other's roles as customer and clerk. They come to this common ground by observing the context of the store and making assumptions from similar past experiences. The common ground information is so rich that Alberta and Benjamin can complete the joint action in less than 15 words. In fact, coordination in a joint action relies on common ground; it is explicitly expressed in the principle of joint salience.

Definition of common ground

In most cases, common ground and context do not need much explanation because they are intuitively understood. We use it naturally all the time when interacting with others. A precise definition of common ground, however, will be helpful in

analyzing how the interfaces we design support common ground. We can identify the common grounds that the interfaces support and can possibly identify other information to add.

To explain the definition of common ground, we will use in example of a joint action continuing in the grocery store. Once Alberta finds the canned olives, she

purchases them at the checkout from the cashier. In the process, Alberta hands the cashier a $5 bill to pay for the canned olives (costing, say, $1.50). Alberta and the cashier have a lot of common ground, however, for this example we focus on the $5 bill. Alberta's action with the bill indicates to her and the cashier that this is how Alberta is paying for the canned olives; it is part of the convention of shopping.

The example illustrates the shared basis definition of common ground. The definition is (Clark 1996, pg. 94):

p is a common ground for members of community C if and only if:

2. b indicates to every member of C that every member of C has information that b holds;

3. b indicated to members of C that p.

In the example, proposition p is that Alberta is paying for the canned olives. The community is Alberta and the cashier. The basis, b, is the $5 bill that Alberta is handing the cashier.

A derivative definition of common ground expresses the participants’ mental representation of the situation, that is the participants’ awareness of the situation. It eliminates the mention of the shared basis. This is the reflexive definition of common ground (Clark 1996, pg. 95):

p is a common ground for members of C if and only if: (i) the members of C have information that p and that i.

In our example, Alberta and the cashier believe p and believe that the other person believes it too.

Of the two definitions, the shared basis definition is more fundamental than the reflexive definition. Besides the participants believing the same proposition, the belief has to be based on the same basis. If not, one participant's assumption of the other is based on incorrect information. This might lead to confusion between the participants as they continue to converse.

An issue with these definitions of common ground is that of containing self reference. The self reference in the case of Alberta is: Alberta is aware that she is

handing the $5 bill and that she has this awareness. In traditional logic self-references are not allowed because they lead to paradoxes, such as Russell's Paradox and a liar's

Paradox. Self-references, however, are part of certain logics.

Categories of common ground

Commons ground comes in many forms. In this subsection, we review three categories of common ground:

1. Initial common ground: Facts and assumptions that participants presumed to have of each other at the start of a joint activity.

2. Current state of the joint activity: The current state the participants assume the joint activity to be in.

3. Joint activity specific: Events and actions that have happened so far in the joint activity.

It is in the interest of the participants to establish the largest common ground possible. The more information that is available, the more they can refer to it efficiently using, for example, verbal shorthand. They can also explore the topic of the discussion in more depth. If the participants require more information to be common ground than they have, they have to establish it by taking time to discuss and explain it.

Initial Common Ground

Before participants even start a joint action, they already have a wealth of common ground they can use. The common ground comes from the setting of the joint action, the participants’ roles, and the participants’ affiliated communities.

Given a setting and the participants’ roles, participants have the common ground to assume the possible goals of a joint action. For example in the grocery store, it is assumed that the customers purchase goods with the help of the clerks and cashiers. The joint actions the participants pick are related to the shopping topic.

The communities that participants belong to determine how the participants can interact. Communities can be nationality, profession, hobbies, language, disabilities, etc. Participants belong to multiple communities; however in a joint action, a person can use only information that participants understand of a shared community. If a participant is an outsider to the community, that person’s information will be much more vague than an insider’s information about the community. People are very quick and accurate at assessing other participants’ affiliations at the start of an interaction.

• Human nature in the most general sense applies to all communities, such that we live on planet earth, experience gravity and other Newtonian forces, and have basic senses (although some senses might be disabled).

• Lexicons determine the kind of language used, such as dialects, jargon, or slang • Cultural facts, norms, procedures: For example a national community shares

common background (e.g. history), customs, and social roles

• Ineffable background information is that obtainable only by personally

experiencing it. Deaf and Blind communities have many of these experiences. It is difficult for an outsider to these communities to gain the same experience. Although an outsider could simulate the experience for some time, it would be difficult to have a full appreciation of having the disability all the time.

People working together from communities with disabilities and communities without disabilities have to take advantage of multiple communities. Related to the abilities/disabilities community, people with and without disabilities are outsiders to each other’s communities. This could possibly lead to misunderstanding, such as a hearing person making a gesture that would be considered impolite in the Deaf community.

The people have to take advantage of other communities they belong to. For example, two employees at a company working on a project can exploit these communities they belong to. They have detailed information about the culture of the company and background on the project.

Current state

A physical model is a powerful way to represent the common ground information related to the current state of a joint activity. Participants can view and manipulate the physical model. For collaborators working through computer mediation (the topic of this dissertation), a shared collaborative application is such a physical model.

To explain the features of a physical model, consider again that Alberta is

purchasing a cart full of goods from the cashier. The main part of the physical model is a typical grocery store checkout counter with a conveyor belt that Alberta puts the goods on and another conveyor belt that the cashier places the rung-up items on. Also the cash

to pay for the goods is part of the physical model. Let's refer to the items to be purchased and cash as markers in the physical model.

Markers contribute information about the common ground in three ways. First a marker’s position has meaning; items to be rung-up are on one conveyor belt, and afterwards on the other conveyor belt. Second, markers are easy to manipulate and thereby reflect a corresponding change in the common ground. Third, participants can simultaneously access the physical model either to make changes or direct their attention to a desired part.

Overall, the physical model is reliable and an effective memory aid. It is reliable because as markers are manipulated all participants can easily view the change. Also, if the participants are distracted from the joint action, when they return to the joint action, they can scan the physical model to remember what the current state of the joint action was.

Joint activity specific

Throughout a joint activity, new common ground is established or built on other common ground. A participant's actions perceived by other participants become part of the common ground; that is, everyone can refer back to it. This common ground, however, is specific to the current joint activity and future joint activities based on the current one. Consider, for example, participants designing a solution to a problem, the participants might have discussed three possible solutions. In the progress of the

discussion the participants can easily refer back to them possibly by an agreed upon name or index.

For joint action participants with and without disabilities, they can lay out

conventions at the start. A deaf person and hearing person can agree on basic gestures for the most often repeated actions. A blind person and a sighted person can agree on the state of the shared physical model (maybe the sighted person explains it to the blind person).