New Media | The Web in a Nutshell

Clients and Servers

• The tool most people use on the Web is a browser, such as Netscape Navigator, Internet Explorer, Opera, Mozilla, or Lynx.
• Web browsers work by connecting over the Internet to remote machines, requesting specific documents, and then formatting the documents they receive for viewing on the local machine.
• The language, or protocol, used for web transactions is Hypertext Transfer Protocol, or HTTP. The remote machines containing the documents run HTTP servers that wait for requests from browsers and then return the specified document. The browsers themselves are technically HTTP clients.

Uniform Resource Locators (URLs)

• One of the most important things to grasp when working on the Web is the format for URLs. A URL is basically an address on the Web, identifying each document uniquely (for example, https://www.art-lesson-plans.com). Since URLs are so fundamental to the Web, we discuss them here in a little detail.

  • The simple syntax for a URL is:
    • http://host/path
  • host
    • The host to connect to: www.oreilly.com or www.google.com. (While many web servers run on hosts beginning with www, the www prefix is just a convention.)
  • path
    • The document requested on that server. This is not the same as the filesystem path, as its root is defined by the server.
    • Most URLs follow this simple syntax. A more generalized syntax, however, is:

      scheme://host/path/extra-path-info?query-info

  • scheme
    • The protocol that connects to the site. For web sites, the scheme is http; for FTP, the scheme is ftp.
  • extra-path-info and query-info

  For optional information used by CGI programs, search CGI overview on the web.
  

• HTML documents also often use a "shorthand" for linking to other documents on the same server, called a relative URL. An example of a relative URL is images/webnut.gif. The browser knows to translate this into complete URL syntax before sending the request. For example, if http://www.oreilly.com/books/webnut.html contains a reference to images/webnut.gif, the browser reconstructs the relative URL as a full (or absolute) URL, http://www.oreilly.com/books/images/webnut.gif, and requests that document independently (if needed). Often in this book, you'll see us refer to a URI, not a URL. A URI (Universal Resource Identifier) is a superset of URL, in anticipation of different resource naming conventions being developed for the Web. For the time being, however, the only URI syntax in practice is URL; so while purists might complain, you can safely assume that "URI" is synonymous with "URL" and not go wrong (yet).

Web Content: HTML, XML, CGI, JavaScript, and PHP

• While web documents can conceivably be in any format, the universal standard is Hypertext Markup Language (HTML), a language for creating formatted text interspersed with images, sounds, animation, and hypertext links to other documents anywhere on the Web. Chapter 2-Chapter 8 cover the current version of HTML.

• In 1996, a significant extension to HTML was developed: Cascading Style Sheets (CSS). Cascading Style Sheets allow web site developers to associate a number of style-related characteristics (such as font, color, spacing, etc.) with a particular HTML tag. This enables HTML authors to create a consistent look and feel in a set of documents.

• While HTML remains the widespread choice for web site development, there is an heir apparent called XML (Extensible Markup Language). XML is a meta-language that allows you to define your own document tags.

• XHTML is a more rigorous version of HTML—essentially, an XML-compliant version of HTML. As such, its syntax and tags are (mostly) the same as HTML.
  • When static documents aren't sufficient for a web site's needs, you can use tools such as CGI, JavaScript, mod_perl, and PHP.
  • CGI is a way for the web server to call external programs instead of simply returning a static document.
  • JavaScript and PHP are both programming languages embedded directly into HTML documents, but that's where the similarities end:
    • JavaScript is used primarily for client-side scripting, and
    • PHP is used primarily for database access.

   

The HTTP Protocol

• In between clients and servers is the network, which uses TCP (Transmission Control Protocol) and IP (Internet Protocol) to transmit data and find servers and clients. On top of TCP/IP, clients and servers use the HTTP protocol to communicate. Details on the HTTP protocol you must understand for writing CGI programs, server scripts, web administration, and just about any other part of working with a server.

What About Web Services?

• "Web Services" is the name given to technologies such as SOAP and XML-RPC, which use existing Internet-related technologies (HTTP, XML, RPC) to exchange data between applications. Web services are so-called because they use the HTTP protocol, but as far as the Web is concerned, it's just another type of content. They're more interesting to networked application developers than to web developers.
• The runaway leader among Unix-based web servers is Apache. Configuring Apache can be left to defaulsts during installation, while various Apache modules can be started to enhance and customize your services. Regardless of the type of server you're running, there are various measures you can take to maximize its efficiency. Optimization techniquesare available for both the server side and the client side.

Who are the Webmasters

• So if that's the Web in a nutshell, who are the webmasters?
  • The title "webmaster," or "web developer", vaguely means a person who works on the content end of the web.
  • When you examine what webmasters actually do, there are many different definitions.
  • On a typical web site, the responsibilities can be broken into four general groups:
    • Content providers ...
      • work on the data itself—creating or editing HTML documents, incorporating images and forms, and maintaining the integrity of the links.
    • Designers ...
      • create the images and also define the "look" of the site.
    • Programmers ...
      • write CGI, Java, JavaScript, and other programs to incorporate to the web site.
    • Administrators ...
      • make sure that the server is running properly and efficiently at all times. They might also be responsible for establishing new content development areas, writing new scripts, and maintaining the security of sensitive documents and of the site in general.
  • On a large site, you might have a staff of 50 content providers, a group of five designers, 3 or 4 programmers, and 2 administrators. On a small site, one person might do it all herself.
  • Each of these people might justifiably call themselves "webmasters." A programmer may not be especially interested in HTML syntax or server configuration, and someone who works only in HTML markup may not need to know anything about HTTP.

Biliography

1. Webmaster in a Nutshell: A Quick Desktop Reference. Spainhour, Stephen and Eckstein, Robert. Sebastopol CA, O'Reilly & Associates, Inc. 2003.