rules are placed on data fields to make sure the data is entered into the database in the correct form
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what is data redundancy
Storing the same data in multiple places
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Why is data redundancy a problem?
it makes updating data harder as you have to change each instance of that data item and it takes up unnecessary storage
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what is data independence
data storage characteristics do not affect data access
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what are is data integrity
refers to data being correct for it's whole lifetime
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how do you increase data integrity
data should be queried and updated for its whole lifetime
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what are the 3 types of data integrity
Entity, Referential, Domain.
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What is entity integrity?
Means that the value of a primary key can not be null and must be unique
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what is referential integrity
Whenever a foreign key value is used, it must reference a valid existing primary key in the parent table in order to maintain the accuracy and consistency of the data within a relationship.
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what is domain integrity
All attributes in the database are related to the overall domain that the database is working on
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what is normalisation
normalising data turn flat file databases into relational databases
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why is normalising good
reduces data redundancy makes multiple linked tables and gives you the ability to restrict tables (adding access levels)
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What is first normal form?
all field names must be unique all values in a field must be atomic all values in a field must have only one data type each table must have a primary key
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what is second normal form
remove any partial dependencies
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what is third normal form
No non-key dependencies (transitive)
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what is an index
an index is a data structure that allows for faster searching of data and lower access times
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what are critical safety related systems
they are computer systems that cannot fail under any circumstance as failure can cause death, severe injury or environmental damage - these systems must have contingencies in place when an error occurs so that manual control can be gained
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what are some types of safety systems
failsafe systems fault tolerant systems autopilot
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explain failsafe systems
manual overrides are in place for when an error occurs when an error occurs the staff are notified and the system will work long enough for a human to regain control
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explain fault tolerant systems
they have redundant systems in place they are split into sections when a section fails it can be bypassed and redundant systems can be bought back online this gives time to a maintenance team to get the system working again
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what is auto pilot
its a fail passive system it allows the user to be there in person while the system is working if an error occurs they can take manual control there and then
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what goes into making a critical safety system
these systems must be fault tolerant and cannot fail under any circumstance. extensive testing must be done by specialised professionals in order to make sure the system is secure.
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what is a control system
Computer systems that CONTROL MACHINERY, rather than produce an output for humans to respond to. E.g. Central heating systems, Traffic light systems
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how have control systems affected the work place
they have taken over many low skill manual labour jobs but have added many jobs in tech. these machines do not need rest, have quicker and more precise construction and can work 24/7
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what social issues have automation in the work place caused
many people in manual labour have been fired due to this (though it usually affects poorer areas). people have to learn to work along side machines and people have become wary that machines will take over all jobs
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what are some drawbacks of automation in the work place
high upfront cost to integrate them into the work place electricity cost to run them can be high need specialised staff to manage them may still need human intervention need to train staff to work with robots
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what are expert systems
systems that hold the knowledge of many experts in a database, these systems can be accessed by people to receive a high quality output. (knowledge bases/ interference engines)
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what are the benefits of an expert system
they have the knowledge of many people easy to update and maintain they can be easily accessed by people in remote areas they are available 24/7 they can be used as second opinions to people they can learn they use centralised decision making
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what are different types of OS
single user, multi user, multi tasking and multi programming
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explain single user OS
otherwise known as a standalone, single user OS allows one active user on the computer at a time. the user will gain full access to the computer and all its resources. the OS will create a home directory for each user. the user will store all their files here. each home directory can only be accessed by the user on their account.
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Explain a multi-user OS
this is when multiple computers can connect to one more powerful computer (that acts like a server). this connection can be physical or remote. the hardware connecting the computers are called terminals. the main computer allows for time sharing of system resources. each user will have their own peripherals.
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Explain multi-tasking
this is when several tasks appear to be running simultaneously. the processes share processer time. the OS will swap tasks when the time slice of the current process ends. this happens at a rate that makes it look simultaneous
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Explain multi processing
this is a method of optimising the CPU so that it does not go idle while waiting for a slower process to finish. the OS will give each task a predetermined chunk of processor time and swap them accordingly. multiple jobs are stored on main memory at the same time
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why does data need to be encrypted
in the age where so much information is digitally transferred if not for encryption our data would be vulnerable and easily accessible to anyone
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What is symetric encryption
a single key is used to encrypt and decrypt data this is quick and easy to set up can be broken quite easy the key is shared so if an attacker knows the encryption method they can reverse an get your data best used on personal device files
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What is asymetric encryption
2 keys are used one will only encrypt the data and one will only decrypt the data the encryption key can be publicised and it would not effect the data's security as if anyone is able to intercept the data they would need the private key only the recipient will have the private key keys can stay intact for many years takes a while to set up may add length to the data best used for online transactions
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how can an XOR gate be used for encryption
decide on a key (the more bits the better) and pass the data and key though an XOR to toggle the data with the key
if using with symmetric encryption use first if using with asymmetric encryption you can use it on top to turn the data into something else
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what makes a good cypher
must work on all data types if there is an error it should not effect the message should be easy to minimise error the level of security is proportional to the effort to decode
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how can statistical analysis be used on an encrypted piece of data
A and E are the most common letter so the attacker can look for letter patterns to try get to the message
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what is a relational database
they are databases that are linked using primary and foreign keys. they reduce data redundancy, make searching and updating data much easier, allow for access levels to be put into place and support complex queries
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