1.3 Exchanging Data Flashcards
How does lossy compression work
Unnecessary information is removed
How does lossless compression work
All information is retained so file is replicated exactly and patterns in the data are recorded
What files use lossy compression
JPG - quality is lost
MP3- Frequencies and sounds that can not be heard are removed
What is an entity (databases)
Category of object, person, event or thing of interest to an organisation about which data us to be recorded
What is an identifier (databases)
Uniquely identifies the entity (known as primary key in relational database)
What is the secondary key (database)
Any index that is not the primary key of a table
What are the possible relationship between entities
1-1
1-many
many-many
What is a foreign key (databases)
Links two tables in a relational database
What is a composite primary key (databases)
A primary key that consisted if mire than one attribute
What is an attribute (databases)
An identifying piece of information that serves to define further and expand the primary key
What is referential integrity
Ensuring that a component in tables linked in a relational database are not deleted
What is an index (databases)
Gives the position of each record according to its primary key
One or more secondary indexes may be defined
How is data captured
Manual methods (transcribing) Magnetic Ink Character Recognition
Optical Character Recognition
Smart card readers
Scanners
Barcode readers
How is data selected and managed
Speed cameras
SQL, data may be used to produce reports, send letters or email
How is data exchanged
Electronic Data Interchange
Transaction software processes
What are internet service providers
Connect directly to backbone cables connected by trans continental lines fed across the sea beds and distribute the internet connection to smaller providers who in turn provide access to individual homes and businesses
What is an URL
Full address of an internet resource, it specifies location of a resource on the internet, including resource name and usually the file type so a browser can request it from a website server
What are internet registrars
Hold records of all existing website name names and the details of those domains that are available for purchase
What are internet registries
Organizations that manage and allocate Internet resources like IP addresses within specific geographic regions.
What does the domain name do
Identifies domain that an internet resource resides In.
What is a domain name server
Domain names structured into a hierarchy of smaller domains and written as a string separated by full stops as dictated by the rules of the dns
What are global directories
DNS catalogues all domain names and IP addresses here
Servers can access them to find the correct IP address location for a resource
What happens when a user enters the URL
Browser requests IP address from local DNS
Keeps asking DNS servers till IP address is located
Once it is located a data request is sent by users computer to the location to find the web page data
What is a fully qualified domain name
Includes the host server name