10 Lists

10.1 Introduction to lists

• Unordered information.
• Ordered information.
• Definitions.

The previous list, for example, is an unordered list, created with the UL element:

<UL>
<LI>Unordered information. 
<LI>Ordered information. 
<LI>Definitions. 
</UL>

An ordered list, created using the OL element, should contain information where order should be emphasized, as in a recipe:

1. Mix dry ingredients thoroughly.
2. Pour in wet ingredients.
3. Mix for 10 minutes.
4. Bake for one hour at 300 degrees.

Definition lists, created using the DL element, generally consist of a series of term/definition pairs (although definition lists may have other applications). Thus, when advertising a product, one might use a definition list:

Lower cost

The new version of this product costs significantly less than the previous one!

Easier to use

We've changed the product so that it's much easier to use!

Safe for kids

You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee).

defined in HTML as:

<DL>
<DT><STRONG>Lower cost</STRONG>
<DD>The new version of this product costs significantly less than the
previous one!
<DT><STRONG>Easier to use</STRONG>
<DD>We've changed the product so that it's much easier to use!
<DT><STRONG>Safe for kids</STRONG>
<DD>You can leave your kids alone in a room with this product and
they won't get hurt (not a guarantee).
</DL>

Lists may also be nested and different list types may be used together, as in the following example, which is a definition list that contains an unordered list (the ingredients) and an ordered list (the procedure):

The ingredients:

• 100 g. flour
• 10 g. sugar
• 1 cup water
• 2 eggs
• salt, pepper

The procedure:

1. Mix dry ingredients thoroughly.
2. Pour in wet ingredients.
3. Mix for 10 minutes.
4. Bake for one hour at 300 degrees.

Notes:

The recipe may be improved by adding raisins.

The exact presentation of the three list types depends on the user agent. We discourage authors from using lists purely as a means of indenting text. This is a stylistic issue and is properly handled by style sheets.

10.2 Unordered lists (UL), ordered lists (OL), and list items (LI)

<!ELEMENT UL - - (LI)+                 -- unordered list -->
<!ATTLIST UL
  %attrs;                              -- %coreattrs, %i18n, %events --
  >
<!ELEMENT OL - - (LI)+                 -- ordered list -->
<!ATTLIST OL
  %attrs;                              -- %coreattrs, %i18n, %events --
  >

Start tag: required, End tag: required

<!ELEMENT LI - O (%flow;)*             -- list item -->
<!ATTLIST LI
  %attrs;                              -- %coreattrs, %i18n, %events --
  >

Start tag: required, End tag: optional

Ordered and unordered lists are rendered in an identical manner except that visual user agents number ordered list items. User agents may present those numbers in a variety of ways. Unordered list items are not numbered.

Both types of lists are made up of sequences of list items defined by the LI element (whose end tag may be omitted).

<UL>
   <LI> ... first list item...
   <LI> ... second list item...
   ...
</UL>

Lists may also be nested:

<UL>
     <LI> ... Level one, number one...
     <OL> 
        <LI> ... Level two, number one...
        <LI> ... Level two, number two...
        <OL start="10"> 
           <LI> ... Level three, number one...
        </OL> 
        <LI> ... Level two, number three...
     </OL> 
     <LI> ... Level one, number two...
</UL>

<ol>
<li value="30"> makes this list item number 30.
<li value="40"> makes this list item number 40.
<li> makes this list item number 41.
</ol>

10.3 Definition lists: the DL, DT, and DD elements

<!-- definition lists - DT for term, DD for its definition -->

<!ELEMENT DL - - (DT|DD)+              -- definition list -->
<!ATTLIST DL
  %attrs;                              -- %coreattrs, %i18n, %events --
  >

Start tag: required, End tag: required

<!ELEMENT DT - O (%inline;)*           -- definition term -->
<!ELEMENT DD - O (%flow;)*             -- definition description -->
<!ATTLIST (DT|DD)
  %attrs;                              -- %coreattrs, %i18n, %events --
  >

Start tag: required, End tag: optional

Definition lists vary only slightly from other types of lists in that list items consist of two parts: a term and a description. The term is given by the DT element and is restricted to inline content. The description is given with a DD element that contains block-level content.

  
<DL>
  <DT>Dweeb
  <DD>young excitable person who may mature
    into a <EM>Nerd</EM> or <EM>Geek</EM>

  <DT>Hacker
  <DD>a clever programmer

  <DT>Nerd
  <DD>technically bright but socially inept person

</DL>

<DL>
   <DT>Center
   <DT>Centre
   <DD> A point equidistant from all points
              on the surface of a sphere.
   <DD> In some field sports, the player who
              holds the middle position on the field, court,
              or forward line.
</DL>

Another application of DL, for example, is for marking up dialogues, with each DT naming a speaker, and each DD containing his or her words.

10.3.1 Visual rendering of lists

Visual user agents generally indent nested lists with respect to the current level of nesting.

For both OL and UL, the type attribute specifies rendering options for visual user agents.

For the UL element, possible values for the type attribute are disc, square, and circle. The default value depends on the level of nesting of the current list. These values are case-insensitive.

How each value is presented depends on the user agent. User agents should attempt to present a "disc" as a small filled-in circle, a "circle" as a small circle outline, and a "square" as a small square outline.

A graphical user agent might render this as:

for the value "disc"
for the value "circle"
for the value "square"

For the OL element, possible values for the type attribute are summarized in the table below (they are case-sensitive):

Note that the type attribute is deprecated and list styles should be handled through style sheets.

<STYLE type="text/css">
OL.withroman { list-style-type: lower-roman }
</STYLE>
<BODY>
<OL class="withroman">
<LI> Step one ...  
<LI> Step two ...
</OL>
</BODY>

The rendering of a definition list also depends on the user agent. The example:

<DL>
  <DT>Dweeb
  <DD>young excitable person who may mature
    into a <EM>Nerd</EM> or <EM>Geek</EM>

  <DT>Hacker
  <DD>a clever programmer

  <DT>Nerd
  <DD>technically bright but socially inept person
</DL>

might be rendered as follows:

Dweeb
       young excitable person who may mature into a Nerd or Geek
Hacker
       a clever programmer
Nerd
       technically bright but socially inept person

10.4 The DIR and MENU elements

DIR and MENU are deprecated.

See the Transitional DTD for the formal definition.

The DIR element was designed to be used for creating multicolumn directory lists. The MENU element was designed to be used for single column menu lists. Both elements have the same structure as UL, just different rendering. In practice, a user agent will render a DIR or MENU list exactly as a UL list.

We strongly recommend using UL instead of these elements.