[lisper]

Because it's DRY. With the top-level annotation, the rest of the table spec remains unchanged, so if you change your mind and decide that you really want a display table to be a semantic one or vice-versa you only have to change on thing whereas if you used DIVs you now have to change not only the top level but also every row and cell.

[goto11]

You don't decide on a lark if you want some content to have table semantics or not! Tags are selected to indicate the semantics of the content. Content don't change semantics unless you rewrite it to actually be something different.

In any case, you might just as well decide the table was a list item or headline then, right? So you would need

   <table what-i-actually-mean="ol">...

[lisper]

So two things...

First, one of the reasons HTML has been as successful and widespread as it has been is that mere mortals are able to use it, not just trained software engineers and designers. Mere mortals may not make such decisions on a lark, but they might make the decision incorrectly and have to go back and change it for that reason. Why make more work for yourself than necessary?

Second, making changes is not the only reason to make code DRY. Re-using TR and TD tags is analogous to operator overloading. If you want to add two numbers you want to be able to write x+y and have the compiler figure out whether that means an integer add, a floating point add, etc. You don't want to have to write (say) x II+ y if you want to add two integers, x FF+ y to add two floats, x LL+ y to add two longs, etc. It's the same for table rows and cells. The mental distance between tables-for-layout and tables-for-structure is smaller than the mental distance between integers and floats. It's just annoying to have to keep telling the computer over and over and over again "this is for layout" or "this is for structure" particularly in a case where the number of repetitions can be very, very large. There is no value add in forcing someone to do substantially more typing when the thing being typed contains no additional information that the system does not already have.

[goto11]

> It's just annoying to have to keep telling the computer over and over and over again "this is for layout" or "this is for structure" particularly in a case where the number of repetitions can be very, very large.

I have a hard time understanding this scenario. What kind of content are you working with?

[lisper]

What difference does that make?

[goto11]

I'm trying to understand the scenario you describe in the context of HTML.

[lisper]

If I am inside the context of a <table-for-structure> tag and I want to create a new row then the only kind of row I can create is a <table-row-for-structure>. It makes no sense to put a <table-row-for-display> inside a <table-for-structure> so requiring the programmer to specify <table-row-for-structure> rather than just <table-row> or <tr> is making her do a lot of extra typing for no value add. A <tr> inside a <table-for-structure> is necessarily a <table-row-for-structure> and a <tr> inside a <table-for-display> is necessarily a <table-row-for-display> just as a + operator operating on two integer values is an integer addition and a + operator operating on two floats is a floating point addition. There is no need to force the programmer to do extra typing to specify what is meant by + in a particular context. Likewise there is no need to force the programmer to do extra typing (or thinking) to specify what <tr> means inside a particular context.