9.2 Information Systems and Databases
Glossary
Term Definition
Information The meaning that a human assigns to data. Knowledge is
acquired when information is received
Purpose The aim or objective of the system and the reason the system
exists. The purpose fulfils the needs of those for whom the
system is created.
Environment The circumstances and conditions that surround an information
system. Everything that influences or is influenced by the
system.
Participants People who carry out or initiate information processes within an
information system. An integral part of the system during
information processing.
Information Technology The hardware and software used by an information system to
carry out its information processes
Information Processes What needs to be done to transform the data into useful
information. These actions coordinate and direct the system’s
resources to achieve the system’s purpose.
Organising The information process that determines the format in which
data will be arranged and represented in preparation for other
information processes
Record A collection of facts about an entity. A record comprises of one
or more related data items. Also known as a tuple.
Flat-file database A single table of data stored as a single file. All rows (records)
are composed of the same sequence of fields (attributes). It is
suitable for small applications and they organise data including
characters, fields, key fields, records and files.
Relational Database A collection of two-dimensional tables joined by relationships,
where the organisation of each table is almost identical to a
simple flat file database.
Relational Database A system that performs information processing on the tables
,Management System within relational databases, including processes performed on
(RDBMS) the data as well as processes that create and modify the design
of the tables.
Relationships How tables are linked together. A relationship creates a join
between the primary key in one table and a foreign key in
another. Also the relationship between rows and columns in a
table.
Foreign Keys Fields that contain data that must match data from the primary
key of another table.
Primary Keys A field or combination of fields that uniquely identifies each
record in a table.
Database Schemas A technique for modelling the relationships within a relational
database. Also known as Entity Relationship Diagrams (ERDs)
1:m, one to many The most common type of relationship in a database schema. It
means that for each record in the primary key’s table, there can
exist multiple records in the foreign key’s table.
1:1, one to one These relationships means that at most one record from table A
is associated with one record from table B.
M:m, many to many These relationships between tables in a database occur when a
parent row in one table contains several child rows in the
second table, and vice versa. This relationship cannot be
represented and must be resolved by creating a join table with
two 1:m relationships.
Recursive Relationships When an attribute of a table is joined to the primary key within
the same table.
Referential Integrity A database concept that ensures each foreign key always
matches a related primary key, with the only exception for NULL
values if they are permitted in the foreign key.
Normalisation It is a process that involves removing the possibility of
redundant data and progressively decomposing the design of a
database into a sequence of normal forms.
Redundant Data Refers to unnecessary and duplicate data that wastes storage
space and creates maintenance problems and is what
, normalisation aims to reduce or eliminate.
First Normal Form (1NF) The organisation of the database after the first stage of
normalisation process is complete. First normal form deals with
the removal of repeating attributes across horizontal rows and
ensures each field holds single data items. Requirements are
that each field stores single data items; and there are no
multiple data items within individual fields and no fields are
repeated.
Second Normal Form The organisation of the database after the second stage of
(2NF) normalisation process is complete. Second normal form
removes redundant data within vertical columns or fields.
Requirements are that all tables must be in first normal form;
and every non-key attribute is functionally dependent on the
table’s primary key.
Third Normal Form The organisation of the database after the third stage of
(3NF) normalisation process is complete. Third normal form removes
further redundant data within vertical columns or fields.
Requirements are that all tables must be in second normal
form; and every non-key attribute is functionally dependent
only on the table’s primary key and not on any other attributes
of the table.
Hypertext Bodies of text that are linked in a non-sequential manner. Each
block of text contains links to other blocks of text.
Hypermedia An extension of hypertext to include non-sequential links with
other media types, such as image, audio and video.
Node A point where links are connected. For example, in a computer
network a node is any device connected (linked) to the network.
Navigation Map A navigation map describes the organisation of a hypertext web,
composed of a sketch that includes each node or screen within
the web together with arrows indicating links between nodes.
Hypertext Markup HTML is the primary method of organising hypertext for use on
Language (HTML) the WWW.
Metadata Data that defines or describes other data, such as HTML tags,
data dictionaries and schematic diagrams, all of which are tools
, to define the data within the database.
META tag An HTML tag that is used to store information that describes the
data within a web page. Intended for use by search engines.
Anchor tag An HTML tag that is used to specify all the links within and
between web pages.
URL Universal resource locator used to identify individual files and
resources on the Internet.
Data Independence The separation of data and its management from the software
applications that process the data. It provides the ability of the
organisation of data to be altered without affecting the
software apps.
Data Dependence When software defines the organisation of its own data.
Direct Access Refers to the ability to go to any data item in any order.
Sequential Access Means the data must be stored and retrieved in a linear
sequence.
Off-line Storage Refers to data stored such that it cannot be accessed until the
storage media is mounted into a drive, e.g. magnetic tape,
optical media (CDs, DVDs) and other portable drives like USB.
On-line Storage Refers to data being available immediately to connected
computers, including hard disks within a single computer and
storage devices accessed via a network or over the Internet.
Backup To copy files to a separate secondary storage device as a
precaution in case the first device fails or data is lost.
Recovery The opposite process of backup where the data is retrieved or
restored from the backup copy and placed back into the system.
Encryption The process of making data unreadable to those who do not
possess the decryption key.
Decryption The process of decoding encrypted data using a key, opposite to
encryption.
View (or User View) The restricted portion of a database made available to a user.
Views select particular data but have no effect on the
, underlying organisation of the database.
Search To look through a collection of data in order to locate required
data.
Sort To arrange a collection of items in some specified order.
SQL Structured Query Language, which is a standard computer
language for relational database management and data
manipulation. It is used to query, insert, update and modify
data.
QBE (Query by Example) A visual method for specifying a query. Often search criteria are
entered into fields within what appears to be an empty record.
Centralised Database A single database under the control of a single DBMS. All users
and client applications connect directly to the DBMS.
Distributed Database A set of connected databases stored on multiple computers that
appears to users as a single database.
Fragmentation A type of distributed database that utilises both vertical and
Distributed Database horizontal fragmentation whereby individual data items are
physically stored once only at one single location
Downloading A type of distributed database whereby each server download
Distributed Database copies of data as it is required from remote databases and
stores the data within its local database.
Replication Distributed A type of distributed database whereby the aim is for all local
Database databases to hold copies of all data all of the time.
Search Engine A program that builds an index of website content. Users can
search the indexed content to locate relevant website content.
Collecting The information process that gathers data from the
environment. It includes knowing what data is required, from
where it will come and how it will be gathered.
Displaying The information process that outputs information from an
information system.
Data Validation A check, at the time of data collection, to ensure the data is
reasonable and meets certain criteria.
Glossary
Term Definition
Information The meaning that a human assigns to data. Knowledge is
acquired when information is received
Purpose The aim or objective of the system and the reason the system
exists. The purpose fulfils the needs of those for whom the
system is created.
Environment The circumstances and conditions that surround an information
system. Everything that influences or is influenced by the
system.
Participants People who carry out or initiate information processes within an
information system. An integral part of the system during
information processing.
Information Technology The hardware and software used by an information system to
carry out its information processes
Information Processes What needs to be done to transform the data into useful
information. These actions coordinate and direct the system’s
resources to achieve the system’s purpose.
Organising The information process that determines the format in which
data will be arranged and represented in preparation for other
information processes
Record A collection of facts about an entity. A record comprises of one
or more related data items. Also known as a tuple.
Flat-file database A single table of data stored as a single file. All rows (records)
are composed of the same sequence of fields (attributes). It is
suitable for small applications and they organise data including
characters, fields, key fields, records and files.
Relational Database A collection of two-dimensional tables joined by relationships,
where the organisation of each table is almost identical to a
simple flat file database.
Relational Database A system that performs information processing on the tables
,Management System within relational databases, including processes performed on
(RDBMS) the data as well as processes that create and modify the design
of the tables.
Relationships How tables are linked together. A relationship creates a join
between the primary key in one table and a foreign key in
another. Also the relationship between rows and columns in a
table.
Foreign Keys Fields that contain data that must match data from the primary
key of another table.
Primary Keys A field or combination of fields that uniquely identifies each
record in a table.
Database Schemas A technique for modelling the relationships within a relational
database. Also known as Entity Relationship Diagrams (ERDs)
1:m, one to many The most common type of relationship in a database schema. It
means that for each record in the primary key’s table, there can
exist multiple records in the foreign key’s table.
1:1, one to one These relationships means that at most one record from table A
is associated with one record from table B.
M:m, many to many These relationships between tables in a database occur when a
parent row in one table contains several child rows in the
second table, and vice versa. This relationship cannot be
represented and must be resolved by creating a join table with
two 1:m relationships.
Recursive Relationships When an attribute of a table is joined to the primary key within
the same table.
Referential Integrity A database concept that ensures each foreign key always
matches a related primary key, with the only exception for NULL
values if they are permitted in the foreign key.
Normalisation It is a process that involves removing the possibility of
redundant data and progressively decomposing the design of a
database into a sequence of normal forms.
Redundant Data Refers to unnecessary and duplicate data that wastes storage
space and creates maintenance problems and is what
, normalisation aims to reduce or eliminate.
First Normal Form (1NF) The organisation of the database after the first stage of
normalisation process is complete. First normal form deals with
the removal of repeating attributes across horizontal rows and
ensures each field holds single data items. Requirements are
that each field stores single data items; and there are no
multiple data items within individual fields and no fields are
repeated.
Second Normal Form The organisation of the database after the second stage of
(2NF) normalisation process is complete. Second normal form
removes redundant data within vertical columns or fields.
Requirements are that all tables must be in first normal form;
and every non-key attribute is functionally dependent on the
table’s primary key.
Third Normal Form The organisation of the database after the third stage of
(3NF) normalisation process is complete. Third normal form removes
further redundant data within vertical columns or fields.
Requirements are that all tables must be in second normal
form; and every non-key attribute is functionally dependent
only on the table’s primary key and not on any other attributes
of the table.
Hypertext Bodies of text that are linked in a non-sequential manner. Each
block of text contains links to other blocks of text.
Hypermedia An extension of hypertext to include non-sequential links with
other media types, such as image, audio and video.
Node A point where links are connected. For example, in a computer
network a node is any device connected (linked) to the network.
Navigation Map A navigation map describes the organisation of a hypertext web,
composed of a sketch that includes each node or screen within
the web together with arrows indicating links between nodes.
Hypertext Markup HTML is the primary method of organising hypertext for use on
Language (HTML) the WWW.
Metadata Data that defines or describes other data, such as HTML tags,
data dictionaries and schematic diagrams, all of which are tools
, to define the data within the database.
META tag An HTML tag that is used to store information that describes the
data within a web page. Intended for use by search engines.
Anchor tag An HTML tag that is used to specify all the links within and
between web pages.
URL Universal resource locator used to identify individual files and
resources on the Internet.
Data Independence The separation of data and its management from the software
applications that process the data. It provides the ability of the
organisation of data to be altered without affecting the
software apps.
Data Dependence When software defines the organisation of its own data.
Direct Access Refers to the ability to go to any data item in any order.
Sequential Access Means the data must be stored and retrieved in a linear
sequence.
Off-line Storage Refers to data stored such that it cannot be accessed until the
storage media is mounted into a drive, e.g. magnetic tape,
optical media (CDs, DVDs) and other portable drives like USB.
On-line Storage Refers to data being available immediately to connected
computers, including hard disks within a single computer and
storage devices accessed via a network or over the Internet.
Backup To copy files to a separate secondary storage device as a
precaution in case the first device fails or data is lost.
Recovery The opposite process of backup where the data is retrieved or
restored from the backup copy and placed back into the system.
Encryption The process of making data unreadable to those who do not
possess the decryption key.
Decryption The process of decoding encrypted data using a key, opposite to
encryption.
View (or User View) The restricted portion of a database made available to a user.
Views select particular data but have no effect on the
, underlying organisation of the database.
Search To look through a collection of data in order to locate required
data.
Sort To arrange a collection of items in some specified order.
SQL Structured Query Language, which is a standard computer
language for relational database management and data
manipulation. It is used to query, insert, update and modify
data.
QBE (Query by Example) A visual method for specifying a query. Often search criteria are
entered into fields within what appears to be an empty record.
Centralised Database A single database under the control of a single DBMS. All users
and client applications connect directly to the DBMS.
Distributed Database A set of connected databases stored on multiple computers that
appears to users as a single database.
Fragmentation A type of distributed database that utilises both vertical and
Distributed Database horizontal fragmentation whereby individual data items are
physically stored once only at one single location
Downloading A type of distributed database whereby each server download
Distributed Database copies of data as it is required from remote databases and
stores the data within its local database.
Replication Distributed A type of distributed database whereby the aim is for all local
Database databases to hold copies of all data all of the time.
Search Engine A program that builds an index of website content. Users can
search the indexed content to locate relevant website content.
Collecting The information process that gathers data from the
environment. It includes knowing what data is required, from
where it will come and how it will be gathered.
Displaying The information process that outputs information from an
information system.
Data Validation A check, at the time of data collection, to ensure the data is
reasonable and meets certain criteria.
