Minimal set of rules for making HTML well-formed?

Hi Folks,

Last week there was a suggestion to use SgmlReader to convert HTML to XHTML. After some experimenting, I discovered that SgmlReader has some problems. See below for one such problem.

I’ve decided to implement my own tool to convert HTML to XHTML. I want the tool to make the minimal amount of changes to the HTML -- just make the changes necessary to make the HTML well-formed. As I see it, there are only 4 things that need to be done to make the HTML well-formed:

1. Ensure that attribute values are delimited with either double or single quotes.
2. Ensure that every start tag has a matching end tag.
3. Ensure that elements are properly nested.
4. Ensure that the XML reserved characters ( <, >, &, ', ") are escaped when used in data.

Am I missing anything? If my tool does those 4 things am I guaranteed that the resulting document will be well-formed?  /Roger