Web architecture was built by standing on the shoulders of giants. Writing in The Atlantic magazine in 1945 [Bush and Wang 1945], Vannevar Bush identified the problems in managing large collections of documents and the links we make between them. Bush’s proposal was to consider this as a scientific problem, and among the ideas he proposed was the one of externalizing and automating the storage and management of association links we make in our readings. He also illustrated his ideas with an imaginary device he called the Memex (“memory extension”) that would assist us in studying, linking, and remembering the documents we work with and the association links we weave between them. Twenty years later, Ted Nelson quoted As We May Think and proposed using a computer to implement the idea, using hypertext and hypermedia structures to link parts of documents together. In the late sixties, Douglas Engelbart and the Augment project provided the mouse and new means of interaction and applied them in particular to hypertext editing and browsing. The beginning of the seventies brought the work of Vinton Cerf and the emergence of the Internet, which connected computers all around the world.
By the end of the eighties, Tim Berners-Lee was able to stand on the shoulders of these giants when he proposed a new breakthrough: an architecture for distributing hypermedia on the Internet, which we now know as the WWW. The Web provides a hypertext infrastructure that links documents across the Internet, that is, connecting documents that are not on the same machine. And so the Web was born. The Web architecture includes two important parts: Web clients, the most well known being the Web browser, and Web servers, which serve documents and data to the clients whenever they require it. For this architecture to work, there have to be three initial essential components. First, addresses that allow us to identify and locate the document on the Web; second, communication protocols that allow a client to connect to a server, send a request, and get an answer; and third, representation languages to describe the content of the pages, the documents that are to be transferred. These three components comprise a basic Web architecture as described in Jacobs and Walsh [2004], which the Semantic Web standards, which we will describe later in this book, extend in order to publish semantic data on the Web.
The idea of a web of information was once a technical idea accessible only to highly trained, elite information professionals: IT administrators, librarians, information architects, and the like. Since the widespread adoption of the WWW, it is now common to expect just about anyone to be familiar with the idea of a web of information that is shared around the world. Contributions to this web come from every source, and every topic you can think of is covered.
Essential to the notion of the Web is the idea of an open community: anyone can contribute their ideas to the whole, for anyone to see. It is this openness that has resulted in the astonishing comprehensiveness of topics covered by the Web. An information “web” is an organic entity that grows from the interests and energy of the communities that support it. As such, it is a hodgepodge of different analyses, presentations, and summaries of any topic that suits the fancy of anyone with the energy to publish a web page. Even as a hodgepodge, the Web is pretty useful. Anyone with the patience and savvy to dig through it can find support for just about any inquiry that interests them. But the Web often feels like it is a mile wide but an inch deep. How can we build a more integrated, consistent, deep Web experience?
1.2 Communicating with Data
Suppose you are thinking about heading to your favorite local restaurant, Copious, so you ask your automated personal assistant, “What are the hours for Copious?” Your assistant replies that it doesn’t have the hours for Copious. So you go to a web page, look them up, and find right there, next to the address and the daily special, the opening hours. How could the web master at Copious have told your assistant about what was on the web page? Then you wouldn’t just be able to find out the opening hours, but also the daily special.
Suppose you consult a web page, looking for a major national park, and you find a list of hotels that have branches in the vicinity of the park. You don’t find your favorite hotel, Mongotel. But you go to their web site, and find a list of their locations. Some of them are near the park. Why didn’t the park know about that? How could Mongotel have published its locations in a way that the park’s web site could have found them?
Going one step further, you want to figure out which of your hotel locations is nearest to the park. You have the address of the park, and the addresses of your hotel locations. And you have any number of mapping services on the Web. One of them shows the park, and some hotels nearby, but they don’t have all the Mongotel locations. So you spend some time copying and pasting the addresses from the Mongotel page to the map, and you do the same for the park. You think to yourself, “Why should I be the one to copy this information from one page to another? Whose job is it to keep this information up to date?” Of course, Mongotel would be very happy if the data on the mapping page would be up to date. What can they do to make this happen?
Suppose you are maintaining an amateur astronomy resource, and you have a section about our solar system. You organize news and other information about objects in the solar system: stars (well, there’s just one of those), planets, moons, asteroids, and comets. Each object has its own web page, with photos, essential information (mass, albedo, distance from the sun, shape, size, what object it revolves around, period of rotation, period of revolution, etc.), and news about recent findings, observations, and so on. You source your information from various places; the reference data comes from the International Astronomical Union (IAU), and the news comes from a number of feeds.
One day, you read in the newspaper that the IAU has decided that Pluto, which up until 2006 was considered a planet, should be considered a member of a new category called a “dwarf planet”! You will need to update your web pages, since not only has the information on some page changed, but so has the way you organize it; in addition to your pages about planets, moons, asteroids, and so on, you’ll need a new page about “dwarf planets.” But your page about planets takes its information from the IAU already. Is there something they could do, so that your planet page would list the correct eight planets, without you having to re-organize anything?
You have an appointment with your dentist, and you want to look them up. You remember where the office is (somewhere on East Long Street) and the name of the dentist, but you don’t remember the name of the clinic. So you look for dentists on Long Street. None of them ring a bell. When you finally find their web page, you see that they list themselves as “oral surgeons,” not dentists. Whose job is it to know all the ways a dentist might list themselves?
You are a scientist researching a particular medical condition, whose metabolic process is well understood. From this process, you know a number of compounds that play a role in the process. Researchers around the world have published experimental results about organic compounds linked to human metabolism. Have any experiments been done about any of the compounds you are interested in? What did they measure? How can the scientists of the world publish their data so that you can find it?
Tigerbank lends money to homeowners in the form of mortgages, as does Makobank; some of them are at fixed interest rates, and some float according to a published index. A clever financial engineer puts together a deal where one of Tigerbank’s fixed loan payments is traded for one of Makobank’s floating loan payments. These deals make sense for people who want to mitigate the different risk profiles of these loans. Is this sort of swap a good deal or not? We have to compare the terms of Tigerbank’s loan with those of Makobank’s loan. How can the banks describe their loans in terms that participants can use to compare them?
What do these examples have in common? In each case, someone has knowledge of something that they want to share. It might be about their business (hours, daily special, locations, business category), or scientific data (experimental data about compounds, the classification of a planet), or information about complex instruments that they have built (financial instruments). It is in the best interests of the entities with the data to publicize it to a community of possible consumers, and make it available via many channels: the web page itself, but
