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Modifying XHTML 1.0 with old-style embedded objects

History of this document

The Literary Moose (sic) wrote this explanation for this activity in 2004. The original site has since been deleted, and the replacement site does not contain this explanation or any of the examples it linked to. Those examples have been removed from this restored document. Perhaps the original author will restore the origian documents. (2006.07.11)

Introduction

It is very easy to modify an existing XHTML 1.0 document type. There are many methods of including non-standard content in your documents, including extending the standard. This article outlines the simplest method, that of modifying the DTD directly. To this end, we consider a set of applications that are nonstandard, yet used everywhere from Kamchatka to the Aleuts and back again: the old-style embed tag used by Flash, Windows Media, QuickTime, Real, SMIL, and SAMI.

Disclaimer

This article is not maimed by any flavor of evangelism, in any direction. It is a technical manual you may wish to follow or not. Yet if you do, it would be recommended that you know what you are doing, and why.

Getting ready

We choose the XHTML 1.0 Strict DTD, since it allows for identifiers to be added to the root element, thus enabling users worldwide to use the CSS signature in a most efficient manner. [...]

Adding an embed tag to the DTD

The regular object tag is included in the special elements group in our DTD:

<!ENTITY % special "%special.pre; | object | img">

Therefore it is natural that we add embed as one more special element:

<!ENTITY % special "%special.pre; | object | img | embed ">

Now, once this is added, embed is already permitted as content, but it isn’t yet defined. It makes sense to try to make it similar to the definition of the object, hence we search the long (and horribly white-space-formatted) original DTD for the definition of object. Alongside, we will add the definition for embed. We find this defintion:

<!ELEMENT object (#PCDATA | param | %block; | form | %inline; | %misc;)*>

The embed tag, to my knowledge, is not used for forms, nor does it have the param child element, so we delete this from the list when we create a definition for embed, like so:

<!ELEMENT embed (#PCDATA | %block; | %inline; | %misc;)*>

This is an element definition. It says that pure text can appear within the embed tag, as do block-level elements (but not forms), inline elements, and miscellanea. Now we need to add attributes.

<!ATTLIST embed
%attrs;
pluginspage %URI; #IMPLIED
src %URI; #IMPLIED
type %ContentType; #IMPLIED
quality %Text; #IMPLIED
height %Length; #IMPLIED
width %Length; #IMPLIED
name NMTOKEN #IMPLIED
tabindex %Number; #IMPLIED
>

This list of attributes, like the element definition, reflects the definition of object, with redundant attributes removed.

%attrs
This allows for regular attributes to be added to embed tag, like id, class, xml:lang, etc.
pluginspage
This is an “embed” version of the codebase attribute for object. We define it as URI
src
Likewise, an URI
type
%ContentType; is used to allow for regular HTML types being added
quality
This attribute takes a value that is of text type (high, low), so we define it as text
height, width
No changes; this is how it is done for all elements that have them defined, as %Length;
name
I am not sure whether name is actually used for embed, but I included it just in case. If it is not used, one may delete it easily
tabindex
%Number;, the regular tabindex

The end result is that we have a custom DTD that will enable us to validate our pages that include the infernal embed tag.

Custom DOCTYPE

[Note: The DTD URL below does not work as of July 2006.]

Including the modified DTD in a document is easy, and requires few modifications:

<!DOCTYPE html PUBLIC
"-//LiteraryMoose//DTD XHTML-Enhanced//EN"
"http://www.literarymoose.info/=/dtd/embed/xhtml1-strict-embed.dtd"
>

The DTD is public. The first address is "-//identity-of-dtd-creating-entity//DTD XHTML-desired-suffix//EN". Then, we add an absolute URI where the DTD resides, so that the validator can parse the DTD upon validation.

Extensions

[...] What follows is a series of examples encompassing other technologies that are in common use.

Apple QuickTime

The list of QuickTime-specific attributes is very long. Once we have an embed element defined, what remains to be done is to define the attributes. Recall the existing attribute list:

<!ATTLIST embed
%attrs;
pluginspage %URI; #IMPLIED
src %URI; #IMPLIED
type %ContentType; #IMPLIED
quality %Text; #IMPLIED
height %Length; #IMPLIED
width %Length; #IMPLIED
name NMTOKEN #IMPLIED
tabindex %Number; #IMPLIED
>

The new attributes are:

  1. autohref
  2. autoplay
  3. cache
  4. controller
  5. correction
  6. dontflattenwhensaving
  7. enablejavascript
  8. endtime
  9. fov
  10. goton
  11. hidden
  12. hotspotn
  13. href
  14. kioskmode
  15. loop
  16. moveid
  17. moviename
  18. node
  19. pan
  20. playeveryframe
  21. qtextn
  22. qtsrc
  23. qtsrcchokespeed
  24. qtsrcdontusebrowser
  25. scale
  26. starttime
  27. target
  28. targetcache
  29. tilt
  30. urlsubstitute
  31. volume

A hefty list! Let us sort our 31 attributes by their meaning. The attributes that use plain text as value are:

  1. autohref
  2. autoplay
  3. cache
  4. controller
  5. correction
  6. enablejavascript
  7. kioskmode
  8. loop
  9. playeveryframe
  10. scale
  11. target
  12. targetcache

The attributes that use integers as values are:

  1. fov
  2. moveid
  3. node
  4. pan
  5. qtsrcchokespeed
  6. tilt
  7. volume

The attributes that use URI as a value are:

  1. goton
  2. hotspotn
  3. qtextn
  4. qtsrc

The attributes that are compact are:

  1. dontflattenwhensaving
  2. hidden
  3. qtsrcdontusebrowser

The moviename is defined as the regular name, which leaves us with three problematic attributes:

  1. endtime
  2. starttime
  3. urlsubstitute

The first two require us to add a new entity: <!ENTITY % Time "CDATA">.

There is no method that I know of that would enable us to use angle brackets inside values, hence the urlsubstitute attribute remains undefined. Quoting Apple:

Replaces every instance of String with SubstituteURL inside any HREF tracks, sprite action URLs, or VR hotspot URLs. Both String and SubstituteURL must be surrounded by angle brackets, and the two must be separated by a colon. The value n may be any integer from 1 to 999, and may be omitted if only one URLSUBSTITUTE parameter is specified. Use this parameter to repurpose QuickTime movies with embedded URLs without editing the movies.

The following is an attribute list that includes all Apple-specific attributes bar one:

<!ATTLIST embed
%attrs;
autohref %Text; #IMPLIED
autoplay %Text; #IMPLIED
cache %Text; #IMPLIED
controller %Text; #IMPLIED
correction %Text; #IMPLIED
dontflattenwhensaving (dontflattenwhensaving) #IMPLIED
enablejavascript %Text; #IMPLIED
endtime %Time; #IMPLIED
fov %Number; #IMPLIED
goto1 %URI; #IMPLIED
height %Length; #REQUIRED
hidden (hidden) #IMPLIED
hotspot1 %URI; #IMPLIED
kioskmode %Text; #IMPLIED
loop %Text; #IMPLIED
movieid %Number; #IMPLIED
name NMTOKEN #IMPLIED
node %Number; #IMPLIED
pan %Number; #IMPLIED
playeveryframe %Text; #IMPLIED
pluginspage %URI; #IMPLIED
qtext1 %URI; #IMPLIED
qtsrc %URI; #IMPLIED
qtsrcchokespeed %Number; #IMPLIED
qtsrcdontusebrowser (qtsrcdontusebrowser) #IMPLIED
quality %Text; #IMPLIED
scale %Text; #IMPLIED
src %URI; #REQUIRED
starttime %Time; #IMPLIED
tabindex %Number; #IMPLIED
target %Text; #IMPLIED
targetcache %Text; #IMPLIED
tilt %Number; #IMPLIED
type %ContentType; #IMPLIED
volume %Number; #IMPLIED
width %Length; #REQUIRED
>

Note: I added only one attribute for hotspot, goto, and qtext. The sad fact is that if you want to have more than one, you will have to add each of them by hand to your DTD. Hey, don’t blame me, I wasn’t the one who wrote the software!

Windows Media Player

The good news is that Windows Media Player uses the param element to define switches, therefore there is nothing to add in our DTD.

RealPlayer

RealPlayer uses the param element to define switches within the object tag, yet it also uses the embed tag, with a handful of custom attributes: controls and console, both of which take the value of text.

<!ATTLIST embed
%attrs;
autohref %Text; #IMPLIED
autoplay %Text; #IMPLIED
cache %Text; #IMPLIED
console %Text; #IMPLIED
controller %Text; #IMPLIED
controls %Text; #IMPLIED
correction %Text; #IMPLIED
dontflattenwhensaving (dontflattenwhensaving) #IMPLIED
enablejavascript %Text; #IMPLIED
endtime %Time; #IMPLIED
fov %Number; #IMPLIED
goto1 %URI; #IMPLIED
height %Length; #REQUIRED
hidden (hidden) #IMPLIED
hotspot1 %URI; #IMPLIED
kioskmode %Text; #IMPLIED
loop %Text; #IMPLIED
movieid %Number; #IMPLIED
name NMTOKEN #IMPLIED
node %Number; #IMPLIED
pan %Number; #IMPLIED
playeveryframe %Text; #IMPLIED
pluginspage %URI; #IMPLIED
qtext1 %URI; #IMPLIED
qtsrc %URI; #IMPLIED
qtsrcchokespeed %Number; #IMPLIED
qtsrcdontusebrowser (qtsrcdontusebrowser) #IMPLIED
quality %Text; #IMPLIED
scale %Text; #IMPLIED
src %URI; #REQUIRED
starttime %Time; #IMPLIED
tabindex %Number; #IMPLIED
target %Text; #IMPLIED
targetcache %Text; #IMPLIED
tilt %Number; #IMPLIED
type %ContentType; #IMPLIED
volume %Number; #IMPLIED
width %Length; #REQUIRED
>

Ready to go.

Synchronized Multimedia Integration Language (SMIL) and Synchronized Accessible Media Interchange (SAMI)

This set of applications requires a different document-type declaration, and content delivery, and therefore is outside of the scope of this small article.

Version history

2004.03.31
Received and posted
2006.07.11 12:16
Restored and updated