Friday, August 04, 2006

Symbol Grounding and the Symbolic Theft Hypothesis 

Symbol Grounding and the Symbolic Theft Hypothesis by Angelo Cangelosi, Alberto Greco and Stevan Harnad.

"The Origin and Grounding of Symbols

Scholars studying the origins and evolution of language are also interested in the general issue of the evolution of cognition. Language is not an isolated capability of the individual, but has intrinsic relationships with many other behavioral, cognitive, and social abilities. By understanding the mechanisms underlying the evolution of linguistic abilities, it is possible to understand the evolution of cognitive abilities. Cognitivism, one of the current approaches in psychology and cognitive science, proposes that symbol systems capture mental phenomena, and attributes cognitive validity to them. Therefore, in the same way that language is considered the prototype of cognitive abilities, a symbol system has become the prototype for studying language and cognitive systems. Symbol systems are advantageous as they are easily studied through computer simulation (a computer program is a symbol system itself), and this is why language is often studied using computational models.

A symbol system is made up by a set of arbitrary “physical tokens” (i.e., symbols) that can be manipulated on the basis of explicit rules (i.e., syntax). Some of the main properties of such a symbol system are: (a) compositeness, that is symbols and rules can be recursively composed; and (b) semantic interpretability, specifying that the entire system and its parts can be systematically assigned a meaning (Pylyshyn, 1984; Harnad, 1990). Some significant issues arise when studying such symbol systems as a direct metaphor and model of language. These will also have direct implications for the study of the origins and evolution of language. The first issue is to establish exactly what a symbol is, by giving a clear and unambiguous definition of it. Subsequently, the process of how symbols take their meanings needs to be understood, for example by studying the symbol grounding problem. Finally, questions regarding the evolution of symbols and symbol manipulation abilities need to be addressed. "

Linked Data - Design Issues 

Linked Data - Design Issues: "Browseable graphs
So now we have looked at ways of making a link, let's look at the choices of when to make a link.

One important pattern is a set of data which you can explore as you go link by link by fetching data. Whenever one looks up the URI for a node in the RDF graph, the server returns information about the arcs out of that node, and the arcs in. In other words, it returns any RDF statements in which the term appears as either subject or object.

Formally, call a graph G browsable if, for the URI of any node in G, if I look up that URI I will be returned information which describes the node, where describing a node means:

1. Returning all statements where the node is a subject or object; and
2. Describing all blank nodes attached to the node by one arc.


(The subgraph returned has been refered to as 'minimum Spanning Graph (MSG [@@ref] ) or RDF molecule [@@ref], depending on whether nodes are considerd identified if they can be expressed as a path of function, or reverse inverse functional properties. A concise bounded description, which only follows links from subject to object, does not work.)

In practice, when data is stored in two documents, this means that any RDF statements which relate things in the two files must be repeated in each. So, for example, in my FOAF page I mention that I am a member of the DIG group, and that information is repeated on the DIG group data. Thus, someone starting from the concept of the group can also find out that I am a member. In fact, someone who starts off with my URI can find all the people who are in the same group."

Monday, July 31, 2006

RDF and Metcalf's Law 

The Sun BabelFish Blog : The Sun BabelFish Blog: "RDF and Metcalf's law

I am trying to find a way of adapting Metcalf's law to the Semantic Web.

My initial intuition is that something like this is true:

'the value of your information grows exponentially with your ability to combine it with new information.'"

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