The 
                  longdesc element contains the primary description of the associated image, graphic or visually-oriented structure.
                  
               
               The 
                  longdesc should contain a comprehensive explanation of the referenced item. See the 
                  
                     summary
                      element for information on how to include a compact description.
                  
               
             
            Usage Example
<d:longdesc xml:id="longdesc01">
    <p>The diagram shows the processes of evaporation, condensation, evapotranspiration, water 
        storage in ice and snow, and precipitation…</p>
    <p>The parts of the diagram, from upper left, moving across the top to the right are: a mountain 
        showing water storage as ice and snow, the sky, clouds and the sun; in the lower right and 
        moving to the left across the bottom to the left are: the ocean…</p>
</d:longdesc>
    Allowed parents
            d:body
               
            
            Allowed children
            This element may contain text.
            
            This element may contain the following children: abbr, 
               address (block variant), 
               address (phrase variant), 
               annoref, 
               annotation (block variant), 
               annotation (phrase variant), 
               aside, 
               block, 
               ssml:break, 
               caption, 
               char, 
               citation (block variant), 
               citation (phrase variant), 
               code (block variant), 
               code (phrase variant), 
               d, 
               definition, 
               description, 
               d:description, 
               emph (text variant), 
               emph (phrase variant), 
               expansion, 
               xforms:group, 
               hd, 
               xforms:input, 
               rend:linebreak, 
               list, 
               ln, 
               m:math, 
               name, 
               note (block variant), 
               note (phrase variant), 
               noteref, 
               num, 
               object (block variant), 
               object (text variant), 
               object (phrase variant), 
               p, 
               pagebreak, 
               ssml:phoneme (text variant), 
               ssml:phoneme (phrase variant), 
               ssml:prosody (text variant), 
               ssml:prosody (phrase variant), 
               quote (block variant), 
               quote (phrase variant), 
               xforms:range, 
               ref, 
               xforms:repeat, 
               its:ruby, 
               s, 
               ssml:say-as (text variant), 
               ssml:say-as (phrase variant), 
               xforms:secret, 
               sel:select (Block variant), 
               sel:select (Phrase variant), 
               xforms:select, 
               xforms:select1, 
               span (text variant), 
               span (phrase variant), 
               sub, 
               ssml:sub (text variant), 
               ssml:sub (phrase variant), 
               sup, 
               table, 
               term, 
               xforms:textarea, 
               time, 
               ssml:token (text variant), 
               ssml:token (phrase variant), 
               transition, 
               verse and 
               w
               
            
            Content model and additional requirements
            
               optional attributes: 
@about, 
                  
@by, 
                  
@class, 
                  
@content, 
                  
@continuation, 
                  
@datatype, 
                  
@desc, 
                  
@its:dir, 
                  
@its:translate, 
                  
@property, 
                  
@rel, 
                  
@resource, 
                  
@rev, 
                  
@role, 
                  
@sel:selid, 
                  
@ssml:onlangfailure, 
                  
@typeof, 
                  
@xml:base, 
                  
@xml:id, 
                  
@xml:lang and 
                  
@xml:space 
               a choice of
                  
                  either 
one or more of 
                     
                     any of the 24 elements: 
address, 
annotation, 
aside, 
block, 
caption, 
citation, 
code, 
d:description, 
description, 
hd, 
list, 
m:math, 
note, 
object, 
p, 
pagebreak, 
quote, 
sel:select, 
ssml:break, 
table, 
transition, 
verse, 
xforms:group and 
xforms:repeat 
                     
                   
                  
                  or 
one or more of 
                     
                     a choice of either one of the 53 elements: 
abbr, 
address, 
annoref, 
annotation, 
char, 
citation, 
code, 
d, 
definition, 
emph, 
emph, 
expansion, 
its:ruby, 
ln, 
m:math, 
name, 
note, 
noteref, 
num, 
object, 
object, 
pagebreak, 
quote, 
ref, 
rend:linebreak, 
s, 
sel:select, 
span, 
span, 
ssml:break, 
ssml:break, 
ssml:phoneme, 
ssml:phoneme, 
ssml:prosody, 
ssml:prosody, 
ssml:say-as, 
ssml:say-as, 
ssml:sub, 
ssml:sub, 
ssml:token, 
ssml:token, 
sub, 
sup, 
term, 
time, 
w, 
w, 
xforms:input, 
xforms:range, 
xforms:secret, 
xforms:select, 
xforms:select1 or 
xforms:textarea 
                        or text
end of choice 
                     
                   
                  end of choice 
               Note that in addition to restrictions presented in the content model  above, 
                  					use of this element must also respect the following requirement:
                  
                     - The 
                        
longdesc element must neither be empty nor contain only whitespace.
                        
                      
                  
                  Such requirements take precedence over any conflicting statements in the
                     						content model or in the lists above of allowed children and parents.
                  
                
             
            Namespace
            http://www.daisy.org/ns/z3998/authoring/features/description/