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Another example using headings

Another example using headings. Suppose we want to write a web document which has two main sections. Suppose the first section has two subsections And suppose the second section has three subsections

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Another example using headings

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  1. Another example using headings

  2. Suppose we want to write a web document which has two main sections • Suppose the first section has two subsections • And suppose the second section has three subsections • Thus, there exists Section 1, Section 1.1, Section 1.2, Section 2, Section 2.1, Section 2.2, Section 2.3

  3. We represent this structure using headings • <BODY> • <H1> Section 1 </H1> • <H2> Section 1.1 </H2> • <H2> Section 1.2 </H2> • <H1> Section 2 </H1> • <H2> Section 2.1 </H2> • <H2> Section 2.2 </H2> • <H2> Section 2.3 </H2> • </BODY>

  4. Of course, there would be text • <BODY> • <P> • This manual is divided into two main sections. • </P> • <H1> Section 1 </H1> • <P> • This section has two sub-sections. </P> • <H2> Section 1.1 </H2>

  5. Lists • A very common kind of structure to have in a document is a list • A list is specified in HTML by enclosing it • between a pair of tags • There are different kinds of lists, including: • unordered lists • ordered lists

  6. Example lists • An ordered list: • 1. January • 2. February • 3. March • An unordered list: • wine • bread • cheese

  7. Tagging lists • Ordered lists are contained between the <OL> and </OL> tags • Unordered lists are contained between the <UL> and </UL> tags • In each type of list, a list item is tagged by putting it between an <LI> and </LI> tag

  8. <OL> • <LI> Janvier </LI> • <LI> Fevrier </LI> • <LI> Mars </LI> • </OL>

  9. <UL> • <LI> Wine </LI> • <LI> Bread </LI> • <LI> Cheese </LI> • </UL>

  10. Using Hyperlinks to Structure Documents: Anchor Tags

  11. Traditional tree-like structure:

  12. Trees can be laid out in a linear fashion: • Book • Chapter 1 • Section 1 • Section 1.1 • Section 1.2 • Section 2 • Chapter 2 • Section 2

  13. But some information structures are more complicated:

  14. But some information structures are more complicated:

  15. That is, some documents are not trees, but are graphs: • Each node in the last slide is a page describing some entity, either a city or a person • In the description of each person, there is a link to the description of his home-town • In the description of each city, there is a link to the description of the person who is its mayor

  16. HTML allows us to specify documents which are graphs: • The tool which HTML provides for building graph-like documents is called an anchor

  17. Anchors

  18. Anchors • An anchor appears in one document

  19. Anchors • An anchor appears in one document • But it usually points to another document

  20. Anchors (contd.): • An anchor is enclosed within a pair of tags: • the start anchor tag <A> • the end anchor tag </A>

  21. Anchor Tags • Until now, we have seen only simple tags • The start anchor tag, <A>, is a structured tag • that is, it has sub-parts • The sub-parts of a tag are called attributes • The start anchor tag, <A>, can have several attributes • for now, we will look at only one attribute, the HREF attribute

  22. Anchor tags (contd.) • A start anchor tag with a HREF attribute looks like this • <A HREF=“some-URL”> • Some examples: • <A HREF=“http://student.cs.ucc.ie/cs4400/ra1”> • <A HREF=“http://www.ucc.ie”> • <A HREF=“htp://www.microsoft.com”>

  23. Anchors (contd.) • An anchor points from one web page to another web page • The HREF attribute in the start tag of the anchor says where the anchor is pointing • We still have to specify what the anchor looks like in the document where it appears • This is done by specifying the content that lies between the <A> and </A> tags

  24. <HTML> • <HEAD> <TITLE> The City of Cork </TITLE> </HEAD> • <BODY> • <H1> Cork </H1> • <P> • Cork is the second-largest city in Ireland. • It's mayor is • <A HREF="http://www.iol.ie/people/fred.htm"> Fred O'Connor </A>. • It's population is ... • </P> • </BODY> • </HTML>

  25. <HTML> • <HEAD> <TITLE> The City of Cork </TITLE> </HEAD> • <BODY> • <H1> Cork </H1> • <P> • Cork is the second-largest city in Ireland. • It's mayor is • <A HREF="http://www.iol.ie/people/fred.htm"> Fred O'Connor </A>. • It's population is ... • </P> • </BODY> • </HTML>

  26. Anchors can be placed anywhere normal document content can appear: • They can appear in the middle of paragraphs of text, as we have seen • They can appear as items in list, (as seen in the next slide)

  27. <HTML> • <HEAD> <TITLE> Politics in Ireland </TITLE> </HEAD> • <BODY> • <H1> Presidents </H1> • <P> • The presidents of Ireland are: • </P> • <OL> • <LI> <A HREF="http://www.iol.ie/pres/hyde.htm"> Douglas Hyde </A> </LI> • <LI> <A HREF="http://www.iol.ie/pres/kelly.htm"> Sean T. O'Kelly </A></LI> • <LI> <A HREF="http://www.iol.ie/pres/dev.htm"> Eamon De Valera </A></LI> • <LI> ...</LI> • </OL> • </BODY> • </HTML>

  28. Anchors can be placed anywhere normal document content can appear: • They can appear in the middle of paragraphs of text, as we have seen • They can appear as items in list • They can even appear in headings (as seen in the next slide)

  29. <HTML> <HEAD> <TITLE> Politics in Ireland </TITLE> </HEAD> <BODY> <H1> Presidents </H1> <H2> <A HREF="http://www.iol.ie/presidents/hyde.htm"> Douglas Hyde </A> </H2> <P> He founded the Gaelic League ... blah blah ... </P> <H2> <A HREF="http://www.iol.ie/presidents/dev.htm"> Eamon de Valera </A> </H2> <P> He took part in 1916 ... blah blah ... </P> </BODY> </HTML>

  30. Organizing groups of anchors: • Frequently, all the anchors in a document have HREFs that are very similar: • <A HREF="http://www.iol.ie/pres/hyde.htm"> Douglas Hyde </A> • <A HREF="http://www.iol.ie/pres/kelly.htm"> Sean T. O'Kelly </A> • <A HREF="http://www.iol.ie/pres/dev.htm"> Eamon De Valera </A> • It would be good if we could avoid having to repeat the common parts of these HREFs • HTML provides the <BASE> tag to meet this need

  31. <HTML> • <HEAD> • <TITLE> Politics in Ireland </TITLE> • <BASE HREF=“http://www.iol.ie/pres/”> • </HEAD> • <BODY> • <H1> Presidents </H1> • <P> • The presidents of Ireland are: • </P> • <OL> • <LI> <A HREF="hyde.htm"> Douglas Hyde </A> • <LI> <A HREF="kelly.htm"> Sean T. O'Kelly </A> • <LI> ... • </OL> • </BODY> • </HTML>

  32. The <BASE> tag: • This appears within the <HEAD> element of a HTML specification: <HEAD> <TITLE> some-title </TITLE> <BASE HREF=“some-URL” > </HEAD> • The HREF in a <BASE> tag is prepended to whatever HREFs appear in <A> tags

  33. The <BASE> tag: • Thus • <BASE HREF=“http://www.iol.ie/pres/”> • ... • <A HREF="hyde.htm"> Douglas Hyde </A> • <A HREF="kelly.htm"> Sean T. O'Kelly </A> • is equivalent to • <A HREF=”http://www.iol.ie/pres/hyde.htm"> Douglas Hyde </A> • <A HREF=”http://www.iol.ie/pres/kelly.htm"> Sean T. O'Kelly </A>

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