Representation

Unit two : M150 : AOU

By : Mais M. Fatayer

1. Introduction

When we communicate with others we use conventions. These conventions can be cultural: a raised thumb means OK in the United Kingdom and the United States but can have a totally different meaning in other cultures.

When people communicate with computers and computers communicate with other computers there is an equally important need for conventions. This unit explores this issue .

2. Communication, convention and representation Communication is the act of transfering

information. Communication also governs our relationship

with computers in two major ways: Communicate with other persons Solve problems, which implies :

Human being to computer Computer to human being Computer to computer

Different ways of communication with others using electronic communications Internet connectivity Chatting Email

Email behavior and conventions Appropriate use of any means of communication

requires people to follow a set od conventions or guidelines

Netiquette is the name for the collection of guidelines setting out appropriate email behavior.

Email has limited scope , unlike face to face conversation which tolerate much more than the spoken words. These implicit feelings are not easy to understand from email message.

In addition to netiquette , email users have developed tricks to impart the tone of a message.

Emails contains some interesting abbreviations , for example: <IMHO> stands for ‘ in my humble opinion’ <this is FYI> stands for ‘ this is for your

information> Smileys , :) ;) x

Problems can come up from not understanding netiquette , like somebody sending a personal reply to an entire mailing list.

Using computers to solve problems Now we continue on same topic,

communication, but we will turn to why communication palys an important role in our relationship with computers?

Simply, because computers help us to solve problems, we need to find good means.

Communication with computers1. Programmers need to instruct computers how to

solve the problem given a variety of inputs. design a problem solver

2. Users need to give computers the inputs to a particular problem. user input

3. Computers need to communicate the solution (or lack of one) back to users. user feedback

4. For tasks or problems which require more than one computer, the computers need to communicate with each other to share the problem. electronic resource feedback

Work in groups to find out how computers transform different types of input to different types of output page 12-13

Communication relies on convention A convention is an agreement between a collection

of participants about what a message means. Conventions might be agreed by: Public convention

Large scale of participants Example: human language

Local convention Medium scale of users Example: referee in different sports, basketball ,football…etc

Private conventions 2 parties Example : cipher text

Conventions ( protocols ) in communicating with computers Communication with and between computers also

relies on conventions. These may be public or local. web addresses are subject to public conventions. where you can visit any web site using a certain

convention, or using the protocol One example , is the HTTP stands for hyper text

transfer protocol, which enables communication between your computer and the computer hosts the web site.

3. Properties of representation To be effective in communication , a

representation must meet at least the following conditions:

1. The form of representation should be perceivable

2. Relationship between form and content is shared by all parties involved in the communication process

1. Representations have to be perceivable Humans different ways of perceiving representations. bellow we

will discuss 3 modes of perception:1. Auditory representations

Perceived as Sound E.g.: spoken languages Computer example?

2. Visual representation Perceived as sight E.g. : written language, traffic signs ,flags, paintings, color a sport

team players wear . Computer example?

3. Tactile representation Perceived by touch Uncommon in human communication Plays central part in communication with computer

Representations: spoilt for choiceFor each icon:

(a) write down what you think it stands for;

(b) suggest an alternative interpretation.

(a)

(a) stands for ‘No smoking’.

(b) is used as a ‘Stop’ sign on Italian roads.

(c) is the symbol for a battlefield on UK Ordnance Survey

maps.

(b)

When stuck on the side of a bin in a smokers’ area, Figure (a)means ‘Do not dispose of burning cigarettes in this bin’.

Figure (b) assumes an understanding of Italian. An alternativeinterpretation might be ‘Meeting point for altos’ at a conference forsingers!

In Figure (c), the two crossed symbols stand for swords. At theentrance of a mountainside restaurant, they might stand for ski-polesin a sign indicating ‘Ski-pole stand for restaurant customers’.

What determines the relationship between form and content in

representations made by people?

Answer:

In representations made by people the relationship between form and

content is not predetermined, but is to a large extent accidental.

People choose which symbol will carry which meaning. In other words,

human choice determines the relationship between form and content.

This does not hamper effective communication as long as all parties

agree on the relationship.

1. Context sensitivity Same form may be associated with different

meanings, based on the context E.g. :

This message is used in two different situations: Situation 1: the board is part of a collection of

safety notices put up by a construction company at the entrance to a construction site

Situation 2: this board is carried around by a group of construction workers in a union demonstration to secure safer working conditions.

2. Ambiguity An ambiguous representation is one which

associates the same form with more than one meaning in the same context.

Human languages are extremely ambiguous ,lets take an example:

Imagine while working on a wildlife project you receive a report which contains the following sentence: ‘Three squirrels ate six chestnuts in the course of the afternoon.’ (a) Do you feel that you understand this sentence?

(b) How many chestnuts were eaten that afternoon?

Ambiguity is not a common feature in the representations designed for computers, since computers can not guess what's in user’s mind, representation have to be explicit and precise

3. Precision

Precision is a measure of the grain (or granularity) of the message representation is able to convey.

For example, digital clocks give the time by displaying numbers, but not all clocks have the same precision. Digital clocks in railway stations typically show hours, minutes and seconds. Alarm clocks tend to show only hours and minutes.

These clocks have a different precision: the one showing seconds has a higher precision than the one displaying hours and minutes only.

Replacing a more precise representation with a less precise one results in information loss. In the clock example, if the station clock were replaced by the alarm clock, there would be information loss because seconds would not be available.

4. Redundancy

A representation contains redundancy if the meaning or content can be recovered from only a part of its form.Redundancy has advantages in situations where part of the form of a representation may be lost; for instance, through faulty transmission. Where the message is really important, redundancy can be added, for instance through repetition, to avoid loss.

Work in groups

Below is a text in English which has been compressed. In the original text, each occurrence of a string of characters from the column marked ‘text’ in the table, has been replaced by the corresponding ‘special symbol’.

@-mo#-guests-@#-a#,-@-cheap[-@-price-p[-p[son-^f[].-2He#-+-a-l+t-^-d+h?.*3

@-mo#-guests-@#-a#,-@-cheap[-@-price-p[-p[son-^f[].-2He#-+-a-l+t-^-d+h?.*3

4. Picking representations

Representations are not equivalent even if they have the same content, and this section shows that they need to be picked with care in order to be fit-for-purpose.

Choosing representations

In previous section we argued that not all representations are equally suitable for a purpose.

See the following example

The meaning of one is the same as the meaning of the other, and road users are expected to be aware of this relationship.

Yet, these two representations cannot be deployed in the same circumstances. explain that?

Fit-for-purposes representations a representation must contain at least

sufficient information for the purpose of the task. Ideally, it should also not be cluttered with irrelevant detail. So precision is relative to what we are talking about.

Figure (a) shows more precise representation than (b), (a) is used by people who travels to these places, where (b) is a hand sketch for a birthday party for example.

Abstraction

Stripping away or irrelevant details is an example of a process called abstraction.

In other words, it’s the process of fitting a problem to a representations which as exactly the information relevant to solving the problem , (as in previous slide)

Complex representation systems

So far, we have dealt with representations as if they were stand-alone entities. This is an oversimplification because few representations are independent and most belong to some complex representation system which is assembled out of simpler representations according to predetermined rules. These rules govern both form and content, so there is a systematic, predictable relationship between a complex form and its meaning.

Complex representation systems have two characteristics:

1. the form of the complex representation is made up of several more basic parts

2. the meaning of the complex representation is constructed from the meanings of the more basic parts in some systematic way.

Example: Traffic signs

Traffic signs are not just a random collection of images on boards. There is a rationale behind these signs, which is useful because it helps people work out what a sign might mean, even if they have never seen it before.

Traffic signs are complex representations. The basic components to a traffic sign are: its shape: triangular signs are warnings; round signs give orders; its color: red signs spell danger or prohibit specific behaviors;

blue signs give positive instructions; its symbol: most symbols are simple, recognizable icons (e.g. a

picture of a bridge) or numbers.

(a) indicates a route only to be used by bicycles. It gives an order (it is round), with a positive instruction (it is blue), involving cycling (it shows a bicycle).

(b) forbids cycling. It gives a prohibiting order (it is red and round), involving cycling.

(c) warns that there may be cyclists around. It gives a warning (it is a triangle), spelling danger (it is red), involving cyclists.

5. Sharing and format

formats have played a key role in ensuring large scale compatibility in a world where computers are connected.

Why do we need format? They ensure consistency. Applications such as browsers

and word processors need to be able to display a document in the same way every time it is opened by a user.

They enable sharing. If a format is shared, or ‘understood’ by two applications, then they can exchange inputs and outputs. This is what allows a word processor, say, to send a document to a printer.

The power of format

In a connected world, compatible applications create commercial opportunities. But formats not only enable sharing: they can also prevent it, and this too may have advantages. For instance, if the format associated with a popular application is made unavailable for sharing (e.g. through copyright, or other legal means), competitors’ applications will be unable to exchange or share. This will have an impact on market share, and serve a range of commercial purposes.

Formats fall into two categories: proprietary formats, made for certain software public formats, made open by the developer

However, rapid rate of application development increases the format confusion, which happens for following reasons: No existing format, (e.g. before invention of digital

cameras) New version,( e.g. text editors format to include colored

font) Dependency between versions,( e.g. office 2007 can

recognize documents created using office 95) Obsolete versions (e.g.: users of MacWord can not open

their document with MS word, because the format of these application is no longer supported.)

Compatibility, standards and conversion There are two ways of achieving compatibility

between formats. The first relies on a wide group of users agreeing to use a particular format. This format then becomes a standard.

The second involves translating between the formats. This is called conversion.

standards

A standard format is one that a large collection of users has agreed to use. The process of agreeing a standard is called standardization, and users can reach agreement in two different ways.

1. Set through deliberate, explicit standardization .A small group of people write down what the standard is, publish the description and keep track of it over time

2. The de facto standards .emerged because there is a large number of people use a particular application

conversion

Another way of achieving compatibility is by making sure that one format can always be translated into another. This process is known as conversion and means that, no matter which format is used, applications will still be able to share, provided their formats can be easily translated into one another. E.g.: MS-Word allow you to save the document using HTML format

What’s in a name

File: a collection of information that is to be kept together in a specific representation, or format.

Give your files names so you can find them again when you need them

Different computer operating systems have different rules for filenames.

Its better to name your TMA file : TMA01M150.html rather than 123.html, why do you think so?

Windows systems list filenames in two parts separated by a dot:

1. the name you provide when saving the file

2. the file extension.

File extensions and what they mean

Thank you