The Semantic Chimera

June 8, 2008

GigaOM has a very good essay about semantic search. What I liked was the inclusion of screen shots of results of natural language queries–that is, queries without Boolean operators. Two systems indexing Wikipedia are available in semantic garb: Cognition here and Powerset here. (Note: there is another advanced text processing company called Cognition Technologies whose url is Don’t confuse these two firms’ technologies.) GigaOM does a good job of making posts findable, but I recommend navigating to the Web log immediately.

Nitin Karandikar reviews both Cognition’s and Powerset’s approach, so I don’t need to rehash that material. For me the most important statement in the essay is this one:

There are still queries (especially when semantic parsing is not involved) in which Google results are much better than [sic] either Powerset or Cognition.

Let me offer several observations about semantic technology applied to constrained domains of content like the Wikipedia:

  1. Semantic technology is extremely important in text processing. By itself, it is not a silver bullet. A search engine vendor can say, “We use semantic technology”. The payoff, as the GigaOM essay makes clear, may not be immediately evident. Hence, the “Google is better” type statement.
  2. Semantic technology is in many search systems, just not given center state. Like Bayesian maths, semantic technology is part of the search engine vendors’ toolkits. Semantic technology delivers very real benefits in functions from disambiguation to entity extraction. As this statement implies, there are many different types of semantics in the semantic technology spectrum. Picking the proper chunk of semantic technology for a particular process is complicated stuff, and most search engine vendors don’t provide much information about what they do, where they get the technology, or how the engineers determined which semantic widget to use in the first place. In my experience, the engineers arrive at their job with academic and work experience. Those factors often play a more important part than rigorous testing.
  3. Google has semantic technology in its gun sights. In February 2007, information became available about Google programmable search engine which has semantics in its plumbing. These patent applications state that Google can discern context from various semantic operations. Google–despite its sudden willingness to talk in fora about its universal search and openness–doesn’t say much about semantics and for good reason. It’s plumbing, not a service. Google has pretty good plumbing, and its results are relevant to many users. Google doesn’t dwell on the nitty gritty of its system. It’s a secret ingredient and no user really cares. Users want answers or relevant information, not a lab demo of a single text processing discipline.
  4. Most users don’t want to type more than 2.2 words in a query. Forget typing well formed queries in natural language. Users expect the system to understand what is needed and the situation into which the information fits. Semantic technology, therefore, is an essential component of figuring out meaning and intention. Properly functioning semantic processes produce an answer. The GigaOM essay makes it clear that when the answers are not comprehensive, on point, or what the user wanted, semantic technology is just another buzz word. Semantic technology is incredibly important, just not as an explicit function for the user to access.

I talk about semantic technology, linguistic technologies, and statistical technologies in this Web log and in my new study for the Gilbane Group. The bottom line is that search doesn’t pivot on one approach. Marketers have a tough time explaining how their systems work, and these folks often fall back on simplifications that blur quite different things. Mash ups are good in some contexts, but in understanding how a Powerset integrates a licensed technology from Xerox PARC and how that differs from Cognition’s approach, simplifications are of modest value.

In my experience, a company which starts out as statistics only quickly expands the system to handle semantics and linguistics. The reason–there’s no magic formula that makes search work better. Search systems are dynamic, and the engineers bolt new functions on in the hope of finding something that will convert a demo into a Google killer. That has not happened yet, but it will. When a better Google emerges, describing it as a semantic search system will not tell the entire story. Plumbing that runs compute intensive processes to cruch log data and smart software are important too.

A demo is not a scalable commercial system. By definition a service like Google’s incorporates many systems and methods. Search requires more than one buzz word.You may also find the New York Times’s Web log post by Miguel Helft about Powerset helpful. It is here.

Stephen Arnold, June 8, 2008


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