[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Required or Optional in DTDs
>Does anyone know what the effects of these are in a DTD, as in, if you >specify an attribute as Required in your DTD, will it bring up an error if >the actual attribute name is missing in your XML file, or just the attribute >value(s)? #REQUIRED means that the attribute must be present; it's quite legal for the value to be an empty string. So if we have: <!ATTLIST foo bar CDATA #REQUIRED> then these are valid: <foo bar="hello"> <foo bar=""> but this is invalid: <foo> There are always syntax errors: <foo bar> <foo bar=> regardless of what is in the DTD. If you want to constrain the value not to be an empty string, there's no way to do precisely that, but several attribute types (eg NMTOKEN) do not allow empty strings. Remember that you will have to use your parser in validating mode to get it to check for required attributes. -- Richard
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|