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Year 10 · ICT · Spring 1 · Effects of IT and ICT applications; databases

ICT applications, part 2: expert systems and control

TheoryPresent ▶

What this lesson covers

6.3 Computer-controlled systems

Cambridge IGCSE ICT 0417 · Topic 6: ICT applications · Paper 1

6.8 Expert systems

Cambridge IGCSE ICT 0417 · Topic 6: ICT applications · Paper 1

6.11 Satellite systems

Cambridge IGCSE ICT 0417 · Topic 6: ICT applications · Paper 1

You will learn to

  • Name and describe the five components of an expert system.
  • Explain how an expert system reaches a conclusion from the user's answers.
  • Describe how robots and production lines are controlled by computer, using sensors.
  • Explain how GPS works and describe one use of GIS.

Success criteria

  • I can name the user interface, inference engine, knowledge base, rules base and explanation system.
  • I can give two uses of expert systems, such as medical diagnosis.
  • I can explain how a sat nav uses satellite signals to find its position.
The syllabus points for these sections
  • Describe how robots are used in manufacturing.
  • Describe production line control.
  • Describe autonomous vehicles as computer-controlled systems.
  • Give advantages and disadvantages of each.
  • Give uses of expert systems.
  • Name and describe the five components of an expert system.
  • Explain how an expert system reaches a conclusion.
  • Give advantages and disadvantages.
  • Explain how GPS and satellite navigation work.
  • Describe what GIS is and how it is used.
  • Describe media communication systems: satellite TV and satellite phones.
  • Give advantages and disadvantages of each.

Key words

Say each word, then read what it means. Every one is in the glossary too.

Computer model
A program that uses rules and formulas to act like a real system.
What if
Changing a model's inputs to see what would happen.
Production line control
Using sensors, computers and robots to run a factory line automatically.
Expert system
Software that copies the knowledge and decisions of a human expert.
Inference engine
The part of an expert system that applies rules to facts to reach conclusions.
Knowledge base
The store of facts in an expert system.
Rules base
The IF … THEN rules in an expert system.
GPS
Global positioning system: satellites that let a receiver work out its position.
GIS
Geographic information system: location data shown as layers on a map.

The explanation

Read it here, or open the study page below to go one step at a time with things to try.

6.3 Computer-controlled systems

Robots, production lines and autonomous vehicles

Factory robots weld car bodies, spray paint, assemble parts, and pack and lift heavy items.

Robots are programmed by writing instructions, or by a person guiding the arm through the task once while the robot records the movements.

In production line control, sensors detect each item on a conveyor belt. Cameras check quality, faulty items are pushed off, and good items are counted and packed automatically.

Autonomous cars, buses, trains and aircraft are computer-controlled systems too. They follow a loop: sensors collect data, the microprocessor compares it with stored data and rules, then actuators steer, brake or accelerate. Their effects are covered in topic 5.

AdvantagesDisadvantages
Work 24 hours a day without breaks, so higher outputVery expensive to buy, install and maintain
Every item made to the same standard, so consistent qualityWorkers lose jobs or need retraining
Can work in dangerous places (fumes, heat, heavy loads), so safer for peopleCannot easily deal with unexpected situations
Lower running costs than paying many workers over timeA fault can stop the whole production line
e.g.Example
A driverless train approaches a station. 1. Sensors detect the platform marker and measure speed. 2. The computer compares the speed with the value needed to stop at the doors. 3. It sends signals to the brakes (actuators). 4. It repeats many times a second until the train stops exactly in place.
6.8 Expert systems

What an expert system is and where it is used

An expert system is software that copies the knowledge and decisions of a human expert in one area.

Uses: medical diagnosis, mineral prospecting (where to dig for oil or metals), car engine fault diagnosis, playing chess, tax advice, and strategy games.

It asks the user questions, applies rules to the answers, and gives a conclusion with a probability, plus an explanation.

The five components

Try the expert system below. It finds out why a laptop will not start. Answer its questions and watch the inference engine apply rules from the rules base (the toy calls it the rule base) to the knowledge base. Then read How I decided: that is the explanation.

ComponentWhat it does
User interfaceAsks the user questions on screen, usually yes/no or multiple choice, and shows the results.
Explanation systemExplains how the system reached its conclusion, and its probability or confidence.
Inference engineThe "thinking" part. Applies the rules to the facts and the user's answers to reach conclusions. Decides which question to ask next.
Knowledge baseStores the facts about the subject, collected from human experts.
Rules baseStores the IF … THEN rules that link facts to conclusions.
e.g.Example
Car fault diagnosis. Rule: IF engine will not start AND lights do not come on THEN battery is flat (90% likely). User interface asks: "Do the lights come on?" User answers: No. Inference engine matches the rule. Explanation system: "Battery fault suggested because the engine will not start and the lights are off."
!Watch out

Learn the five names exactly. "Database" is not the same as "knowledge base", and "processor" is not "inference engine".

There is something to try for this step in the IGCSE library.

Setting up an expert system, and its pros and cons

To build one: interview experts to collect knowledge; build the knowledge base and rules base; build the inference engine; design the user interface and explanation system; test it against known cases.

AdvantagesDisadvantages
Gives consistent answers; does not get tired or emotionalOnly as good as the rules entered; errors give wrong advice
Knowledge of many experts in one systemHas no common sense; cannot handle situations outside its rules
Available 24/7 and in many places at once, even where there is no expertExpensive to set up and keep up to date
Fast; gives probabilities and explains its reasoningUsers may trust it too much; lacks a human expert's empathy
6.11 Satellite systems

GPS and satellite navigation

The global positioning system (GPS) uses at least 24 satellites orbiting the Earth. Each sends signals with its exact position and the exact time, from an atomic clock.

A receiver measures how long each signal took to arrive. That gives its distance from each satellite. Using at least three satellites (usually four for accuracy), it calculates its position, often to within a few metres.

Satellite navigation (sat nav) combines this position with stored maps, so it can show where you are and plan a route.

Advantages of sat navDisadvantages of sat nav
Driver does not need to read a map, so safer and less stressfulMaps may be out of date: new roads or closures missing
Finds the fastest route and reroutes around traffic jamsCan send drivers down unsuitable roads, e.g. lorries on narrow lanes
Finds nearby fuel stations, hotels and car parksSignal can be lost in tunnels, between tall buildings or in dense forest
Spoken directions let the driver watch the roadDrivers lose map-reading skills and rely on it too much

Geographic information systems (GIS)

A GIS stores data linked to locations and shows it as layers on a map. Layers might be roads, rivers, schools, population or flood risk.

Users can switch layers on and off and ask questions, such as "Which homes are within 500 m of the river?"

Uses: emergency services finding the nearest ambulance, town planners choosing where to build, mapping crime, and protecting wildlife.

AdvantagesDisadvantages
Combines many types of data in one view, so patterns are easier to seeExpensive software and data
Helps make better decisions quickly, e.g. in an emergencyNeeds trained users
Data can be updated and shared easilyResults are only as accurate as the data put in

Media communication: satellite TV and phones

Communication satellites relay signals from one place on Earth to another. Many are geostationary: they orbit at about 36 000 km and stay above the same point.

Satellite TV is sent up to a satellite and back down to dishes over a whole continent. Satellite phones connect directly to satellites, so they work in deserts, at sea and in disaster zones with no mobile network.

AdvantagesDisadvantages
Covers huge areas, including remote places with no cablesSignals travel a long way, so there is a delay (latency) on calls
Works when ground networks are damaged, e.g. after an earthquakeHeavy rain or storms can block the signal
One satellite broadcasts to millions of homes at onceSatellites are very expensive to build and launch; repairs are hard
Fast to set up a link anywhereSatellite phones and calls are expensive; need a clear view of the sky

Study it

Open the study page and go one step at a time.

ICT topic 5

The effects of using IT

Step by step, with exam questions and a quiz.

ICT topic 6

ICT applications

Step by step, with exam questions and a quiz.

ICT topic 18

Databases

Step by step, with exam questions and a quiz.

ICT topic 16

Graphs and charts

Step by step, with exam questions and a quiz.

Topic 18 · Year 7

Data, spreadsheets and AI

Data is raw facts. Information is data with meaning. Spreadsheets calculate, databases store and search, AI learns patterns from examples.

Check yourself

One question at a time. The reason shows after each answer.

Saved on this device.