The organising information process prepares the data for use by other information processes. It does this by structuring and representing the data in a form suited to the needs of the subsequent information processes. The organising process does not alter the actual data, rather it modifies the way it is structured and represented. The data itself is still the same.
Organising takes place just before, just after or even as an essential part of other information processes. This is particularly the case in regard to collecting, displaying, storing and retrieving, and transmitting and receiving. The data must be organise into a form that can be used and understood by the display the device during and prior to displaying. When storing data it is first organised into a format suitable for the storing and following retrieval. Transmitting involves the reorganisation of data to conform to the rules required for communication; receiving data involves reversing this organisation process.
The ability to analyse and process data efficiently depends on the way the data is organised. The selection of software that is able to organise data appropriately is critical to the success of all computer-based information systems. If the data is organised appropriately then vital analysing and processing tasks can be completed more efficiently.
Our focus in this chapter is on the strengths and weaknesses of various different software tools, the aim being to make informed decisions when selecting software tools to use within an information system.
We shall examine examples of the following types of software:
· paint and draw software for images.
· mixing software for audio.
· Database software that organises data into tables.
· Website creation software that uses hyperlinks to organise data for web pages.
Paint and Draw Software for Images
Bitmap images are processed using paint software applications and vector images are processed using draw applications. Be aware that many software applications are available that combine the functions of both paint and draw applications.
Paint Software Application
All bitmap images, regardless of their storage format, are processed within paint applications as uncompressed bitmaps. When a compressed bitmap image is opened it is decompressed and organised into a two dimensional arrangement of individual pixels, each pixel representing a particular colour. The processing performed by paint software alters the colour values of individual pixels. When the image is later saved it is first reorganised into the desired storage format. The organisation of the stored data is often quite different to the organisation of the data whilst it is being processed by the application; this is the case for most software applications not just paint applications. For example, JPEG images for use on the web can be stored in such a way that when downloaded, first a low resolution version of the entire image is received, followed by progressively more pixels until the image appears at its full resolution. This organisation of the pixels reflects the often slow and varying speed of Internet connections.
Bitmaps with a colour depth of 24 bits in most cases use the RGB system where 8 bits are used to represent the intensity of red, 8 bits for the intensity of green and 8 bits for the intensity of blue. The RGB system is used as it corresponds directly to the red, green and blue light used by monitors to display images. As 8 bits are able to represent decimal integers from 0 to 255, each colour has a range of intensity from 0 to 255. The screen also provides the facility to alter colours using hue, saturation and luminance values. These values can be entered directly as decimal integers or the mouse can be used on the colour swatch and luminance bar. Moving horizontally across the swatch alters the hue. Hue is the pure colour within the spectrum of light; it ranges from red through yellow, green, blue and then violet. The saturation is changed by moving vertically up and down within the swatch. Saturation is a measure of the dilution of a hue. Luminance is controlled using the luminance bar and it alters the brightness of the colour. Regardless of the method used to edit a colour it is the red, green and blue RGB values that are used by the majority of paint applications, including Microsoft Paint, to represent the colour of each pixel. Some specialised paint applications use other methods of representation such as the hue, saturation and luminance values (HSL) or CMYK. CMYK is an acronym for cyan, magenta, yellow and key. Key really means black but the letter K is used to prevent confusion with the B used in RGB representations. CYMK system is used within professional printing software applications as cyan, magenta, yellow and black correspond to the primary pigments used on commercial four colour printing presses.
Draw software applications
Draw applications are used to process vector images. Vector images are composed of a series of different shapes, or objects, whose individual attributes or properties can be changed independently. Vector images are therefore structured as an arrangement of different objects where each object is represented as a particular type with particular attributes.
As vector images are represented mathematically they can be resized without loss of clarity. Resizing a vector image does not alter the organisation of the vector image data; rather it alters the size of the bitmap used to display the image. Monitors and printers can only display bitmap images, hence a vector image must be organised into a bitmap of the desired resolution prior to display. The mathematical description of each object allows bitmaps to be created at any resolution without loss of clarity. Hence a single vector image can be displayed at the maximum resolution available on the display device.
Processing in draw applications alters the attributes of objects that make up a vector image. Attributes of most objects include; line thickness, fill pattern and colour. Many processes are able to alter the attributes of multiple objects within an image. If a number of objects are selected then it is common for just the attributes present in all the selected objects to be available.
Resizing and reshaping of objects is commonly implemented using handles or nodes.
These nodes are significant points on the object used to determine its shape and size.
On a rectangle or square the four corner points are sufficient to determine its shape and size; these four nodes need only determine the position of each point, joining the points with straight lines creates the shape. More complex shapes use nodes that contain further information used to determine the shape of the line running through the node. Bezier curves are common objects used in draw applications. Many clipart images are composed with nothing but Bezier curves.
The shape of a Bezier curve is determined by the attributes of each node. In simple terms each node contains two points, an anchor point and a control point. In most draw applications each of these points can be selected and moved using the mouse.
The anchor point lies on the curve, whereas the control point is used to define a straight line to the anchor point. This line is always a tangent to the curve; it just touches the curve at the anchor point. Longer lines have more influence over the curve; they appear to attract the curve to them, shorter lines tend to repel the curve.
Within many images it is not the actual Bezier curve itself that forms the images rather it is the fill colour applied to the curve that creates the image. The original brain image used as an icon for many of the group tasks in this text is entirely composed of filled Bezier curves.
Mixing Software for Audio
Audio data is organised as either a series of sound samples or as descriptions of various attributes of each individual note. In this section we restrict our discussion to software applications used to process sampled audio data. It is structured as a sequence of separate samples where each sample represents the amplitude of the sound wave at a particular point in time. For example, every second of CD quality sound contains 44100 samples for both the left and right channels, each of these samples is 16 bits long, in effect an integer in the range 0 to 65535. Software applications that process audio data are able to analyse and alter these sound samples; that is they change the integers used to represent each amplitude sample. As is the case with other software applications, most mixing software is able to organise the data into various formats in preparation for storage and subsequent retrieval, however during processing mixing applications operate on the raw sound samples.
Mixing software is used to alter a sound sample and also to combine sound samples from multiple sources. The processes available within mixing applications operate by automating the alteration of multiple sound samples. Sequences of individual sound samples, in almost all cases, need to change progressively; this ensures that a smooth rise or fall in amplitude is maintained. It would be tiresome to manually edit individual sound samples directly; maintaining appropriate differences between each sample would be near impossible. Most mixing software applications display the sound data graphically as a wave. The amplitude, or height of the wave determines the volume or level of the sound whereas the frequency or number of waves per second determines the pitch of the sound.
The level of a sound is a measure of the relative differences in amplitude. To maintain the fidelity or detail of digital audio it should be collected (recorded) using the widest possible range of amplitudes. For example, if 16 bit samples are used then the loudest sounds in the recording should ideally have a value of 65535. If the level is set low such that the loudest sample is represented as only 32000, then all the sound samples recorded will be compressed to be within a range from 0 to 32000. In effect much of the detail of the original sound will be lost. Often mixing software is used to adjust the average levels of different tracks within a music compilation; this process is called normalisation. Normalised recordings allow listeners to set the volume on their amplifiers once in the knowledge that each track on the compilation will on average play at the same volume.
Some processes in mixing applications alter the sound without analysis of the existing sample e.g. trimming silence, fading in or out, and combining two sounds, whilst others first analyse the sound to determine the nature of the alterations to be made.
Trimming is a process similar to cutting, where parts of the sound are removed; in fact the familiar cut, copy and paste functions are also present in most mixing software. Commonly when sound samples are collected they contain initial periods of near silence and they also conclude with a period of near silence. Such samples will appear on the display as areas with low or zero amplitude. The trim function removes all the sound samples that do not lie within the selected range; hence the trim function reduces the total number of raw sound samples.
Fades progressively alter the level or amplitude of a sound; a fade-in occurs when the sound level progressively increases and a fade-out occurs when the sound level progressively decreases. Fades to do not alter the frequency of the wave so the pitch remains constant.
Combining two sounds so they play simultaneously is commonly used to add additional instruments or vocals to an existing audio track. Such functions are implemented in mixing software using a special case of the familiar paste function, however instead of inserting the new sound samples into the existing data, the new sound samples are combined or mixed with the existing samples. For example, in ‘Cool Edit’ the edit menu contains a ‘Mix Paste…’ function. When this menu item is selected various criteria, including the file to be pasted are specified prior to the mixing process commencing.
Database Software That Organises Data Into Tables
Arranging data into tables is one of the most common methods of data organisation. Each row in a table represents all the data about a particular person or thing. Individual columns contain similar data about each person or thing. For example, a table containing personal contact data would likely include columns for surname, first name, street address, suburb, postcode and phone number (see Fig 4.28). Each row in the table contains all the data about a particular person, hence the data contained in each row is related and should be represented in such a way that it remains together. It makes sense to organise the data in such a way tha the above properties of table data is preserved and even enforced.
Most software applications organise at least some of their data into tables. In many applications this table-based organisation is not obvious to the user. For example, earlier in this chapter we examined the RTF specifications; RTF uses tightly structured font tables, colour tables and paragraph tables. The most obvious applications that utilise tables of data are those based on databases. Most databases are composed entirely of tables of data and furthermore this table organisation is clearly apparent to the user. Hence in this section we concentrate on the organisation of data within simple databases and how this method of organisation assists processing.
The rows in a database table are known as records and each record is composed of fields. The records within a particular table can be considered to be of a particular data type; all records possess the same fields and each field is of the same type, hence each record is also of the same data type.
When creating a database table each field is created with a particular data type together with various other properties; this information is specified using a data dictionary. The data type and all other specified properties of the field are enforced whenever data is entered or edited. Examples of data types commonly available include text, numeric types including integers and floating-point representations, Yes/No or Boolean and even data types capable of storing images, audio and video data.
Another common analysis process performed on tables of data is ordering or sorting data in preparation for display. In a database table the order in which records are physically stored is not significant; conceptually records exist in no particular order.
When a sorting or ordering process is initiated all the records must be arranged into this specified order. When sorts are applied to large tables with many thousands of records this is a potentially lengthy process. How can the data be organised to improve the efficiency of sorts? The answer is to use indexes. Indexes within database tables are similar to those in the back of a book. Think about the index in a book; it provides an alphabetical listing, where each entry points to a specific page. If, rather than the page numbers in the index, you inserted the actual information then the result would be the book sorted into alphabetical order based on the keywords within the index.
In summary, data organised into a table is arranged in rows and columns. All the data in each column or field is of the same data type, hence the method used to represent each data item within a column is identical. The data in a single row or record holds all the data about a single person or thing, all records in a table have the same data type. Most table processing manipulates entire records. For example, a search or sort may display particular fields however in reality entire records are being processed.
Website Creation Software That Uses Hyperlinks to Organise Data for Web Pages
There is an enormous range of website creation software applications available from basic text editors through to professional packages such as Adobe’s Dreamweaver.
There are specialised applications for creating surveys, news sites, discussion forums and various other interactive web sites. Whilst some web pages actually exist as files waiting to be retrieved from a web server, many others are created dynamically based on data collected from users. We cannot hope to examine the functionality of website creation software in any detail; rather we will concentrate on the nature of the hyperlinks created by all such software applications.
Consider all the web pages that can be created dynamically, together with the billions of actual pages stored as files on web servers. The total is infinite. All these pages form the World Wide Web (WWW) and all are linked together using hyperlinks. When a user clicks on a hyperlink they are taken to a related document; this new document may also contain hyperlinks to further documents. As a consequence documents are connected to each other in a highly complex and unstructured manner. Despite the unstructured organisation of hypertext, it better reflects the thought processes of the human mind than other methods of data organisation
Hypertext is a term used to describe bodies of text that are hyperlinked. The related term, hypermedia, is an extension of hypertext to include hyperlinks to a variety of different media types including image, sound, and video. In everyday usage, particularly in regard to the WWW, the word hypertext has taken on the same meaning as hypermedia.
Documents created by website creation software and then accessed via the WWW are primarily based on HTML. HTML is an acronym for hypertext mark-up language and is the primary method of organising hypertext for use on the WWW. Clicking on a link within an HTML document can take you to a document stored on your local hard drive or to information stored on virtually any computer throughout the world.
In general, HTML documents and also other documents that contain hyperlinks are organised as follows:
· All HTML documents are stored as text files. That is, they are arranged as a sequential list of characters where each character is represented using a system similar to the ASCII system.
· Pairs of tags are used to specify hyperlinks and other instructions. Pairs of tags can be nested inside each other.
· Tags are themselves strings of text, they have no meaning until they are analysed and acted upon by software.
· • In HTML, tags are specified using angled brackets < >. Text contained within a pair of angled brackets is understood by web-enabled applications to be an instruction; all other text is displayed.
· • Web browsers, and other web enabled software applications, understand the meaning of each HTML tag. Such applications are able to analyse tags and respond accordingly.
Organising takes place just before, just after or even as an essential part of other information processes. This is particularly the case in regard to collecting, displaying, storing and retrieving, and transmitting and receiving. The data must be organise into a form that can be used and understood by the display the device during and prior to displaying. When storing data it is first organised into a format suitable for the storing and following retrieval. Transmitting involves the reorganisation of data to conform to the rules required for communication; receiving data involves reversing this organisation process.
The ability to analyse and process data efficiently depends on the way the data is organised. The selection of software that is able to organise data appropriately is critical to the success of all computer-based information systems. If the data is organised appropriately then vital analysing and processing tasks can be completed more efficiently.
Our focus in this chapter is on the strengths and weaknesses of various different software tools, the aim being to make informed decisions when selecting software tools to use within an information system.
We shall examine examples of the following types of software:
· paint and draw software for images.
· mixing software for audio.
· Database software that organises data into tables.
· Website creation software that uses hyperlinks to organise data for web pages.
Paint and Draw Software for Images
Bitmap images are processed using paint software applications and vector images are processed using draw applications. Be aware that many software applications are available that combine the functions of both paint and draw applications.
Paint Software Application
All bitmap images, regardless of their storage format, are processed within paint applications as uncompressed bitmaps. When a compressed bitmap image is opened it is decompressed and organised into a two dimensional arrangement of individual pixels, each pixel representing a particular colour. The processing performed by paint software alters the colour values of individual pixels. When the image is later saved it is first reorganised into the desired storage format. The organisation of the stored data is often quite different to the organisation of the data whilst it is being processed by the application; this is the case for most software applications not just paint applications. For example, JPEG images for use on the web can be stored in such a way that when downloaded, first a low resolution version of the entire image is received, followed by progressively more pixels until the image appears at its full resolution. This organisation of the pixels reflects the often slow and varying speed of Internet connections.
Bitmaps with a colour depth of 24 bits in most cases use the RGB system where 8 bits are used to represent the intensity of red, 8 bits for the intensity of green and 8 bits for the intensity of blue. The RGB system is used as it corresponds directly to the red, green and blue light used by monitors to display images. As 8 bits are able to represent decimal integers from 0 to 255, each colour has a range of intensity from 0 to 255. The screen also provides the facility to alter colours using hue, saturation and luminance values. These values can be entered directly as decimal integers or the mouse can be used on the colour swatch and luminance bar. Moving horizontally across the swatch alters the hue. Hue is the pure colour within the spectrum of light; it ranges from red through yellow, green, blue and then violet. The saturation is changed by moving vertically up and down within the swatch. Saturation is a measure of the dilution of a hue. Luminance is controlled using the luminance bar and it alters the brightness of the colour. Regardless of the method used to edit a colour it is the red, green and blue RGB values that are used by the majority of paint applications, including Microsoft Paint, to represent the colour of each pixel. Some specialised paint applications use other methods of representation such as the hue, saturation and luminance values (HSL) or CMYK. CMYK is an acronym for cyan, magenta, yellow and key. Key really means black but the letter K is used to prevent confusion with the B used in RGB representations. CYMK system is used within professional printing software applications as cyan, magenta, yellow and black correspond to the primary pigments used on commercial four colour printing presses.
Draw software applications
Draw applications are used to process vector images. Vector images are composed of a series of different shapes, or objects, whose individual attributes or properties can be changed independently. Vector images are therefore structured as an arrangement of different objects where each object is represented as a particular type with particular attributes.
As vector images are represented mathematically they can be resized without loss of clarity. Resizing a vector image does not alter the organisation of the vector image data; rather it alters the size of the bitmap used to display the image. Monitors and printers can only display bitmap images, hence a vector image must be organised into a bitmap of the desired resolution prior to display. The mathematical description of each object allows bitmaps to be created at any resolution without loss of clarity. Hence a single vector image can be displayed at the maximum resolution available on the display device.
Processing in draw applications alters the attributes of objects that make up a vector image. Attributes of most objects include; line thickness, fill pattern and colour. Many processes are able to alter the attributes of multiple objects within an image. If a number of objects are selected then it is common for just the attributes present in all the selected objects to be available.
Resizing and reshaping of objects is commonly implemented using handles or nodes.
These nodes are significant points on the object used to determine its shape and size.
On a rectangle or square the four corner points are sufficient to determine its shape and size; these four nodes need only determine the position of each point, joining the points with straight lines creates the shape. More complex shapes use nodes that contain further information used to determine the shape of the line running through the node. Bezier curves are common objects used in draw applications. Many clipart images are composed with nothing but Bezier curves.
The shape of a Bezier curve is determined by the attributes of each node. In simple terms each node contains two points, an anchor point and a control point. In most draw applications each of these points can be selected and moved using the mouse.
The anchor point lies on the curve, whereas the control point is used to define a straight line to the anchor point. This line is always a tangent to the curve; it just touches the curve at the anchor point. Longer lines have more influence over the curve; they appear to attract the curve to them, shorter lines tend to repel the curve.
Within many images it is not the actual Bezier curve itself that forms the images rather it is the fill colour applied to the curve that creates the image. The original brain image used as an icon for many of the group tasks in this text is entirely composed of filled Bezier curves.
Mixing Software for Audio
Audio data is organised as either a series of sound samples or as descriptions of various attributes of each individual note. In this section we restrict our discussion to software applications used to process sampled audio data. It is structured as a sequence of separate samples where each sample represents the amplitude of the sound wave at a particular point in time. For example, every second of CD quality sound contains 44100 samples for both the left and right channels, each of these samples is 16 bits long, in effect an integer in the range 0 to 65535. Software applications that process audio data are able to analyse and alter these sound samples; that is they change the integers used to represent each amplitude sample. As is the case with other software applications, most mixing software is able to organise the data into various formats in preparation for storage and subsequent retrieval, however during processing mixing applications operate on the raw sound samples.
Mixing software is used to alter a sound sample and also to combine sound samples from multiple sources. The processes available within mixing applications operate by automating the alteration of multiple sound samples. Sequences of individual sound samples, in almost all cases, need to change progressively; this ensures that a smooth rise or fall in amplitude is maintained. It would be tiresome to manually edit individual sound samples directly; maintaining appropriate differences between each sample would be near impossible. Most mixing software applications display the sound data graphically as a wave. The amplitude, or height of the wave determines the volume or level of the sound whereas the frequency or number of waves per second determines the pitch of the sound.
The level of a sound is a measure of the relative differences in amplitude. To maintain the fidelity or detail of digital audio it should be collected (recorded) using the widest possible range of amplitudes. For example, if 16 bit samples are used then the loudest sounds in the recording should ideally have a value of 65535. If the level is set low such that the loudest sample is represented as only 32000, then all the sound samples recorded will be compressed to be within a range from 0 to 32000. In effect much of the detail of the original sound will be lost. Often mixing software is used to adjust the average levels of different tracks within a music compilation; this process is called normalisation. Normalised recordings allow listeners to set the volume on their amplifiers once in the knowledge that each track on the compilation will on average play at the same volume.
Some processes in mixing applications alter the sound without analysis of the existing sample e.g. trimming silence, fading in or out, and combining two sounds, whilst others first analyse the sound to determine the nature of the alterations to be made.
Trimming is a process similar to cutting, where parts of the sound are removed; in fact the familiar cut, copy and paste functions are also present in most mixing software. Commonly when sound samples are collected they contain initial periods of near silence and they also conclude with a period of near silence. Such samples will appear on the display as areas with low or zero amplitude. The trim function removes all the sound samples that do not lie within the selected range; hence the trim function reduces the total number of raw sound samples.
Fades progressively alter the level or amplitude of a sound; a fade-in occurs when the sound level progressively increases and a fade-out occurs when the sound level progressively decreases. Fades to do not alter the frequency of the wave so the pitch remains constant.
Combining two sounds so they play simultaneously is commonly used to add additional instruments or vocals to an existing audio track. Such functions are implemented in mixing software using a special case of the familiar paste function, however instead of inserting the new sound samples into the existing data, the new sound samples are combined or mixed with the existing samples. For example, in ‘Cool Edit’ the edit menu contains a ‘Mix Paste…’ function. When this menu item is selected various criteria, including the file to be pasted are specified prior to the mixing process commencing.
Database Software That Organises Data Into Tables
Arranging data into tables is one of the most common methods of data organisation. Each row in a table represents all the data about a particular person or thing. Individual columns contain similar data about each person or thing. For example, a table containing personal contact data would likely include columns for surname, first name, street address, suburb, postcode and phone number (see Fig 4.28). Each row in the table contains all the data about a particular person, hence the data contained in each row is related and should be represented in such a way that it remains together. It makes sense to organise the data in such a way tha the above properties of table data is preserved and even enforced.
Most software applications organise at least some of their data into tables. In many applications this table-based organisation is not obvious to the user. For example, earlier in this chapter we examined the RTF specifications; RTF uses tightly structured font tables, colour tables and paragraph tables. The most obvious applications that utilise tables of data are those based on databases. Most databases are composed entirely of tables of data and furthermore this table organisation is clearly apparent to the user. Hence in this section we concentrate on the organisation of data within simple databases and how this method of organisation assists processing.
The rows in a database table are known as records and each record is composed of fields. The records within a particular table can be considered to be of a particular data type; all records possess the same fields and each field is of the same type, hence each record is also of the same data type.
When creating a database table each field is created with a particular data type together with various other properties; this information is specified using a data dictionary. The data type and all other specified properties of the field are enforced whenever data is entered or edited. Examples of data types commonly available include text, numeric types including integers and floating-point representations, Yes/No or Boolean and even data types capable of storing images, audio and video data.
Another common analysis process performed on tables of data is ordering or sorting data in preparation for display. In a database table the order in which records are physically stored is not significant; conceptually records exist in no particular order.
When a sorting or ordering process is initiated all the records must be arranged into this specified order. When sorts are applied to large tables with many thousands of records this is a potentially lengthy process. How can the data be organised to improve the efficiency of sorts? The answer is to use indexes. Indexes within database tables are similar to those in the back of a book. Think about the index in a book; it provides an alphabetical listing, where each entry points to a specific page. If, rather than the page numbers in the index, you inserted the actual information then the result would be the book sorted into alphabetical order based on the keywords within the index.
In summary, data organised into a table is arranged in rows and columns. All the data in each column or field is of the same data type, hence the method used to represent each data item within a column is identical. The data in a single row or record holds all the data about a single person or thing, all records in a table have the same data type. Most table processing manipulates entire records. For example, a search or sort may display particular fields however in reality entire records are being processed.
Website Creation Software That Uses Hyperlinks to Organise Data for Web Pages
There is an enormous range of website creation software applications available from basic text editors through to professional packages such as Adobe’s Dreamweaver.
There are specialised applications for creating surveys, news sites, discussion forums and various other interactive web sites. Whilst some web pages actually exist as files waiting to be retrieved from a web server, many others are created dynamically based on data collected from users. We cannot hope to examine the functionality of website creation software in any detail; rather we will concentrate on the nature of the hyperlinks created by all such software applications.
Consider all the web pages that can be created dynamically, together with the billions of actual pages stored as files on web servers. The total is infinite. All these pages form the World Wide Web (WWW) and all are linked together using hyperlinks. When a user clicks on a hyperlink they are taken to a related document; this new document may also contain hyperlinks to further documents. As a consequence documents are connected to each other in a highly complex and unstructured manner. Despite the unstructured organisation of hypertext, it better reflects the thought processes of the human mind than other methods of data organisation
Hypertext is a term used to describe bodies of text that are hyperlinked. The related term, hypermedia, is an extension of hypertext to include hyperlinks to a variety of different media types including image, sound, and video. In everyday usage, particularly in regard to the WWW, the word hypertext has taken on the same meaning as hypermedia.
Documents created by website creation software and then accessed via the WWW are primarily based on HTML. HTML is an acronym for hypertext mark-up language and is the primary method of organising hypertext for use on the WWW. Clicking on a link within an HTML document can take you to a document stored on your local hard drive or to information stored on virtually any computer throughout the world.
In general, HTML documents and also other documents that contain hyperlinks are organised as follows:
· All HTML documents are stored as text files. That is, they are arranged as a sequential list of characters where each character is represented using a system similar to the ASCII system.
· Pairs of tags are used to specify hyperlinks and other instructions. Pairs of tags can be nested inside each other.
· Tags are themselves strings of text, they have no meaning until they are analysed and acted upon by software.
· • In HTML, tags are specified using angled brackets < >. Text contained within a pair of angled brackets is understood by web-enabled applications to be an instruction; all other text is displayed.
· • Web browsers, and other web enabled software applications, understand the meaning of each HTML tag. Such applications are able to analyse tags and respond accordingly.