<startflag>
The <startflag> element in a DITAVAL
    document specifies information that identifies the beginning of flagged
    content. The information can be an image, alternate text, or
    both.
Usage information
If the <startflag> element does not specify
        an image or provide alternate text, the element has no defined
        purpose.
Rendering expectations
Processors treat the information provided by the
          <startflag> element in the following
        way:
- If an image is specified, the image is used as a flag to
          identify the beginning of the flagged content. If the
            
<alt-text>element contains content, the content is used as alternate text for the image. - If alternate text is specified but the
            
<startflag>element does not specify an image, the alternate text is used to indicate the beginning of the flagged content. 
Content model
<alt-text>?
Contained by
<prop>, <revprop>
Optional <alt-text>
Contained by
<prop><revprop>
Attributes
The following attribute is available on this element:
@imageref- Specifies a URI reference to the image, using the same syntax
            as the 
@hrefattribute. See The href attribute for information on supported values and processing implications. 
@imageref- Specifies a URI reference to the image, using the same syntax
            as the 
@hrefattribute. See The href attribute for information on supported values and processing implications. 
Example
This section is non-normative.
The following code sample shows a DITAVAL document that is used to
        render icons before content that is specific to a particular
        operating system. The <startflag> elements
        specify the icons, and the <alt-text>
        elements specify alternate text.
<val>
  <prop action="flag" att="platform" val="linux">
    <startflag imageref="linux-icon.gif">
      <alt-text>Linux</alt-text>
    </startflag>
  </prop>
  <prop action="flag" att="platform" val="mac">
    <startflag imageref="mac-icon.gif">
      <alt-text>Macintosh</alt-text>
    </startflag>
  </prop>
  <prop action="flag" att="platform" val="windows">
    <startflag imageref="windows-icon.gif">
      <alt-text>Windows</alt-text>
    </startflag>
  </prop>
</val>