|The Semantic Web|
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How did the Semantic Web begin ?
A Brief Aside on Software Agents
Agents Make Communication Easier
Agents Collect, Process and Exchange Web Content
Open Interaction Between Agents
Even Alien Agents Can Understand Each Other
Note: see an updated version of this page on the Home site.
As most things do, the Semantic Web started small. An article in the May 2001 issue of Scientific American described a futuristic world where software agents automatically schedule an entire series of medical treatments via the Semantic Web. The article states that:
Software agents have been a hot topic for about the last 15 years. There are several W3.org and commercial variations of an Agent Standard. In all of them, rules and other powerful conceptual structures are implemented explicitly. The idea of software 'agents' has grown beyond any reasonable expectation in the last few years.
The Wikipedia defines a software agent as:
Agents are generally credited with enabling communication between people and machines in an easier and more natural manner than specialized rule languages and knowledge 'templates'. Later, it may be helpful to think of the five agents listed above as a packaging of semantic services in a form that is useful for a certain type of knowledge-intensive task.
For now, it is important to understand that the Semantic Web is something that software agents use to accomplish useful tasks.
The Scientific American article continues:
There are three important elements to the vision described above.
1 - Collecting, processing and exchanging Web content from diverse sources.
2 - Interaction between agents increasing the effectiveness of the Semantic Web, that is, it creates a synergy.
3 - All agents can work together, even agents who have not been designed to work together.
To what degree has the article's vision of the future realized in the past five years since it was published ?
Early Definitions of the Semantic Web
The Object Web
The ideas of a "Semantic Web" had been around in various guises for several years prior
to the Scientific American article. One precursor of the Semantic
Web was the idea of "Web Objects" or the "Object Web" kicking around in the
mid-1990s. The OMG was a big part of that phase of development of the
It really began to take off when the World Wide Web Consortium (W3C) became the authoritative source of standards for the Semantic Web.
W3 Definition of the Semantic Web
How Data Relates To Objects
A Web of Data
Data, Metadata or Both ?
Distributed Subject Databases
Can Humans Really Read RDF Ontologies ?
to the W3, the most authoritative source of standards, the Semantic
Web is "about two things", that is:
1 - Common formats for interchange of data, where on the original Web we only had interchange of documents
2 - Language for recording how the data relates to real world objects.
They continue, "that allows a person, or a machine, to start off in one database, and then move through an unending set of databases which are connected not by wires but by being about the same thing".
Above all, they see it as a web of data, which is interesting for two reason.
From the Wikipedia: "In general, data consist of propositions that reflect reality. A large class of practically important propositions are measurements or observations of a variable. Such propositions may comprise numbers, words, or images".
Clearly, most of the 'data' in the Semantic Web will be not 'observations' per se but data about data, that is meta-data about the domain ( a price series for hog bellies ) type ( decimal numbers ), the format ( currency ), etc. So, in effect, the W3 is blurring the distinction between data and meta-data. There are no separate data structures for data and meta-data. It is all data.
The second interesting thing is the unending journey of the person or machine through many distributed databases connected by a common thing or subject, something like a distributed subject database.
Also note that the agent can be a software program or a person. That is built in to the definition at this point. But I think it is clear that almost everyone connected with the Semantic Web effort understands that eyeball to eyeball encounters with page after page of arcane XML/RDF/OWL rule definitions is not something that anyone but an enthusiast wants to cope with on a daily basis.
More on the subject of human-readable XML/RDF/OWL later. In fact, this is a major challenge for creating a non-technical tool set usable by ordinary people.
Semantic Web and Markup Languages
The Wikipedia has a good definition of "Semantic Web".
The markup languages mentioned are especially important. There are several levels and layers of standards, some focused on the Web resources such as Resource Description Framework ( RDF ), others on metadata such as eXtendend Markup Language ( XML ). Still others concentrating on expressing query logic ( SPARQL ) or interchange of rule sets ( Rule Interchange Format ) or just business rule logic itself ( Business Rules Markup Language (BRML).
Semantic Web as a Semantic Network
Is It a Knowledge Web ?
The Unification of All Scientific Content !!!
An old concept from AI, the semantic network,
may have a second life in the Semantic Web. In a semantic network,
ontologies of distinct types are interpreted within evaluation networks
that get their meaning from the semantic relations in which they
participate. In a sense, the subjects of the ontolgies discover
their roles by consequence of relationships rather than by declaration or assignment. This
can be seen as a direct result of RDF 'entailment rules' and the consequent 'entailment
In the biological sciences, there is a huge movement afoot to create a workable set of medical ontologies. According the definition of 'semantic web' provided by Genomics & Proteomics ( nestled between 'self-organization and 'semiochemical', the goal is the "unification of all scientific content by computer languages and technologies that permit the interrelationships between scientific concepts to be communicated between machines".
|The Semantic Web as Advanced Search and Search Engines||
A very interesting phenomena is Swoogle,
a sort of Google for the Semantic Web.
There is also an interesting comment on the Swoogle Blog, probably belonging more properly to previous section.
An ambitious example from several years ago ( before the RDF standard and the W3 Semantic Web project is SHOE, which may still have a few lessons for the SW five years later.
Semantic Web as a Wiki on Steriods
On June 26, 2006 at 5:20am EST, the Evolving
Trends web site published an article entitled "Wikipedia 3.0: The End of
Google?". By June 28th, two days later, the article had
reached 650,000 people - by July 1st, it was being referenced by over
6,000 other sites and had been read by close to 2,000,000
Secondly, and more importantly, it seems to demonstrate a growing dissatisfaction with Google approach to classifying knowledge via search engines and indexing. Certainly anyone who has studied the efficacy of the Google indexing paradigm knows that a well-formed Google search may reveal no more than 10% of the interesting sites on a given subject, depending on circumstances. While the resources of Web with a hundred million or so pages was readily accessible by Google, a Web of ten billion pages has apparently overwhelmed the basic indexing and search technology. The information you are looking for is probably out there somewhere, but it may take a long struggle and good luck in order to find it.
Semantic Wikis may provide an alternative to the Google 'knowledge bottleneck'. Google near monopoly on web search combined with its emerging role as global censor of inconvenient truths is probably fueling the dissatisfaction.
Semantic Web is NOT Web 2.0
... Well, Not Exactly.
Another tier of terminology is calling the Semantic Web something like the "Web 2.0",
or more commonly "Web 3.0".
Presumably, earlier advances of "Web 1.0" and "Web
1.5" technology were restricted
to improved content, database integration, graphical widgets, etc.
However, far from clarifying definitions, using the term "Web Number
Whatever" seems to generate yet another level of debate on its
The Wikipedia has an uncharacteristically vague definition of "Web 2.0". The terms "FOAF"and "XFN" mentioned in the quote will be described in detail in the next section, just note that they facilitate social networking between people.
So the bottom line is that Web 2.0 may represent a step in the direction of the Semantic Web, not a ringing endorsement. The Web 2.0 as envisioned lacks the capability for machines to understand the meaning of things
On the other hand, it is becoming clear that the Web 2.0 initiative will represent a step in that direction, and perhaps far more than a small step in term of the way the Semantic Web is used by ordinary, non-technical people in their everyday activities. It will require powerful and sophisticated user interfaces to make the new semantic universe accessible to the non-technical 95% of people in the world rather than the technically inclined 5% of the people. Web 2.0 technology seems to be playing a major role in constructing these interfaces.
A More Humane Machine Readable Language ?
How Humane Is It ?
Does It Translate ?
The proponents of these markup languages represent their creations as an improvement over implementing rules by programming logic, and that is true from the standpoint of flexibility, but I'm not sure if they are any more readable than programming logic to ordinary human beings. But this make the end user completely reliant on ontology editors to interact with the final representation of the knowledge. Are markup languages the strength or the soft underbelly of the Semantic Web ?
It's a critical factor and, in my opinion, there doesn't seem to be a simple way to express rules in both a machine-readable and human readable form at this point of time, although there are some interesting efforts toward Semantic Web editors of various sorts.
There is also an strong international flavor of the Semantic Web, even at this early stage. Unlike the Web 1.0 and maybe the Web 2.0, the Semantic Web "3.0" is not going to be an English only affair Translation to and from some sort of structured English ( or German or Spanish or whatever ) is probably still an absolute requirement for a multi-lingual rule language that is usable by ordinary human beings.