Using XFN with FOAF
So, before I just start splattering your screen with Acronyms, lets define a few, eh?
- FOAF: Friend of a Friend - An XML Schema containing information about you, as well as a small bit of information, or links to information, about the people you know.
- XFN: XHTML Friends Network - A Microformat generally used in links to other sites or pages to identify that person's relevance to you, such as "contact", "friend", "acquaintance", "met", "muse" and etcetera.
Generally, you wouldn't combine an XHTML standard with a different XML Schema. But, I've personally decided the best way to use the two together.
First, declare the XHTML namespace in your FOAF file. This is with all the others, and generally looks like xmlns:xhtml="http://www.w3.org/1999/xhtml".
Next, go to where you have included your contacts. For each <foaf:knows> tag, add inside of it xhtml:rel="contact" or similar, following the XFN standards.
And voila! You now have XFN and FOAF working together. Of course, the only problem is that nobody quite supports this standard yet, but it will hopefully come in the future.
My Guidelines for using XFN in FOAF is that it should be used when referencing another <foaf:Person>. In fact, if you want, you should probably even add xhtml:rel="me" to your own <foaf:Person>.
The Purpose of CSS in the Semantic Web
The Term Web x.x is overused like the bottom of a shoe, and because of such a term, its scoffed at, laughed at, and generally made fun of on any tech site or twitter you can find. However, the term does have some importance attached to it.
"Web 2.0" would best be defined as the Internet for Design. Web 2.0 cares more about the Design side of pages. The Fancy fonts used, the rounded borders, the interactivity (AJAX!). That is definitely what Web 2.0 is all about.
"Web 3.0" is all about Semantics. The important part is that the code can be extracted via a machine or script or something. Here, standards take importance. XML, Microformats; we have to have standards that dictate how to write our code so that a program like Operator can pull the relevant information from it.
Now, once we have a code like that, CSS becomes VERY important. We need to use CSS to position our elements and colour them to make them look useful to the viewer, not just the machine, while still having machine readable code.
You see what I'm getting at? If you still don't understand, try opening a random XML or RSS file (without a CSS, XSL, or XSLT file) in Opera. That's actually perfect rendering of an XML file, and that's what it would be to any ordinary user.
Thankfully, Microformats were designed with Human Readability in mind, so they will properly work (bare minimum) with the HTML that is used with them, but, obviously, CSS is important to make it look like something nice.
So, now you know, the importance of CSS in the Semantic Web. 
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