There are three main approaches I can see that have been attempted to attain this problem- These are shown near the center of the knowledge triangle:
The most ambitious approach involves taking a strongly scientific mindset, as exemplified by the RDF and semantic web. The second involves a more pragmatic, guy in the garage approach, exemplified by the UMLS (the Unified Medical Language System is a system that tries to organize medical information). The third method for achieving this type of system involves sacrificing both scientific precision and simplicity to minimize the effort required by the writer. This third approach is exemplified by the advanced search technologies currently being developed by companies such as Google, Microsoft and Yahoo. Of course, a certain amount of creative tweaking is necessary to fit these ideas so neatly into such a simple graphic, but it allows us to capture some simple truths about these different methodologies. Let's look at each of these in more detail...
RDF and The Semantic Web
The Semantic Web is a vision outlined by Tim Berners Lee, the principal designer of most of the technology that underlies the world wide web and hence was a major enabler of what I have called the second computer revolution. He developed this idea in response to his dissatisfaction with the unstructured nature of the current way that information is generated for the internet. His vision of the future appears similar to that described in this primer.
At its core, the Semantic Web can be thought of as a methodology for linking up pieces of structured and unstructured information into commonly-shared description logics ontologies. For instance, suppose that I owned a sandwich shop and had my menu online, which happened to include the same grilled chicken sandwich that we had discussed previously in our chapter about description logics. If we wanted to, we could take our ontology for sandwiches we had set up earlier and publish it online (in a special format), then link our menu to that published ontology, also in a special format. This special format is callled RDF, which can be used both to describe the items in our description logic, but also is used within the menu to create the actual "link".
However, creating our own ontology is not actually necessary: If an ontology is already available to describe a grilled chicken sandwich then we can directly link to that sandwich instead of creating our own. For instance, after searching online for some RDF ontologies that covers sandwiches, I was able to find wine.rdf on the www.w3.org website. It has a food item called "LightMeatFowlCourse", which roughly describes my grilled chicken sandwich. So when I write the HTML for my website, I could put the following text into my HTML document: