Formal Ontology and Philosophical Content
on the Semantic Web
APA Symposium on Formal Ontology
and Philosophical Content on
the Semantic Web
San Francisco, 28 March 2003
Texas A&M University
Background to the Questions
The Current Paradigm for Searching the Web
The current paradigm for searching and extracting
information from the web is a function of current web
architecture — unstructured text and graphics.
Google: Semantic content inferred (sort of) from web
Employs a clever method of inferring content from the
hyperlinked structure of the web. Note, though, that
this is an inference from structure, NOT from content.
General reliance upon presence of explicit string
representations of desired content.
No explicit inference possible, as content is not
represented in a uniform, processable form with a
fixed, sharable semantics and a corresponding
- E.g., current paradigm does not accommodate
inferences from "fancy place to stay" to "luxury
The Semantic Web I: Canonical Content
XML-based Languages: http://www.w3.org/XML
The next step in the evolution of the web under active
development — the so-called "Semantic Web" —
involves the development of web pages whose content is
explicitly representated in specialized, XML-based formal
These languages are designed with computational
tractability in mind, and hence, expressively, are
sublanguages of full FOL.
- Logic-based languages
Designed for exchange and integration of information
and for metatheory, and hence include (usually
properly) full FOL.
The Semantic Web II: Ontologies and Intelligent Agents
Critical to the success of the Semantic Web will be
the development of software agents that can
extract content from the web in response to complex
queries by reasoning upon its explicit,
- The Need for Ontologies
Typically, however, just as in ordinary discourse,
most explicit content presupposes a vast amount
of implicit, higher-level, "background" information,
That a hotel is a place to stay.
That hotels are typically made of mostly concrete,
steel, and glass.
Implicit background information is crucial for making
That one is likely to find beds in hotels.
That hotels are large, heavy, objects.
That hotels are difficult or impossible to move
from place to place.
That hotels make poor camping equipment.
Background information must therefore be made explicit
to support the inferences needed to support complex
queries to the explicit, distributed content in
next-generation web pages.
Ontologies are explicit representations of
this sort of higher-level background information, and
are thus crucial to the evolution of the Semantic Web.
Some Notable Loci of Formal Ontology
The above suggests a broader, "public service" question
than the first of the advertized questions:
Should philosophers participate in the development of the
Semantic Web? That is, should philosophers, as a discipline,
actively engage in development, refinement, and maintenance of
formal and applied ontologies and reasoning systems to enhance
intelligent search on the World Wide Web?
The Original "Localized" Question
Easy answer: Yes!
Wealth of possibilities for useful philosophical involvement,
both critical and constructive.
Formal ontology development
Formal ontologies the most trenchent point of contact
betweeen the philosophical community and the Semantic
Though, not surprisingly, the point where the work
of philosophers has been drawn upon the most.
Still, most of the actual work still largely done
by carried out by philosophically literate
computer scientists and engineers not themselves
trained as philosophers.
Gruber, Genesereth, Guarino, Grüninger,
Hobbes, Hayes, Sowa, Lenat, Guha
Critiques of applied ontologies
Many, probably most, applied ontologies not developed by
Consequently, many issues familiar to philosophers
are being rehashed by ontology developers, often
with philosophically questionable results.
Consequently, there is a great need for the
critical eyes of trained philosophers to be cast
upon existing ontologies.
Contributions to applied ontologies
Many applied domains (e.g., automobile manufacturing)
present extremely interesting logical and conceptual
Proper representation of time and change.
Choice of ontological primitives.
Career and consulting opportunities.
All of the organizations noted above and many
private businesses are hiring philosophers to
develop applied ontologies.
Solutions to the Integration Problem
Both formal and applied ontology development efforts
tend to focus around some group or individual.
Hence, they tend to be somewhat idiosyncratic.
This raises the specter of a philosophical Tower of Babel.
The problem is not simply one of translating
between ontologies based upon different but
semantically equivalent lexicons.
More typically lexicons and their semantics
Might also find different choices of upper-level
primitives, e.g., endurantism vs perdurantism;
events vs temporally-indexed relations; etc.
Might also find different ontologies are based
upon different upper-level ontologies altogether,
e.g., Upper Cyc vs. SUMO.
Critical that there be some overarching framework that
enables sharing and integration of information in
different ontologies, using different lexicons,
possibly based upon different upper-level ontologies.
Contributions to Automated Reasoning Systems
Many types of reasoning systems of interest to
philosophers and philosophical logicians are
relevant to the intelligent search.
Intensional logics (notably logics of belief)
The logic of common knowledge
Contributions to formal language development
Very large number of difficult issues of form and
expressive power surrounding development of both
XML-based and logic-based languages for the Semantic
Choice of primitives
Integration of languages
- See RDF and KIF/CL mailing list archives
Should (can?) philosophers, as a discipline, build a formal
ontology of philosophical concepts to enhance searching,
linking, and cross-referencing of philosophical content on the
World Wide Web?
Two elements here:
The construction of an "ontology" of philosophical
The use of that ontology to facilitate intelligent search
on the web for peculiarly philosophical content.
A priori: Surely such an ontology would prove useful in
the search for philosophical content if the Semantic Web
architecture is itself feasible.
Two sources of uncertainty:
Feasibility of a general philosophical ontology.
Quality of content returned questionable when the search space
is the entire web in all its anarchic glory.
This leads to the second question:
Should the Stanford Encyclopedia of Philosophy project develop
such a formal ontology for managing the metacontent in its
reference work (i.e., for managing cross-references as entries
come online or are changed, for building other thematic
navigation tools, etc), or will statistical techniques in
computational linguistics suffice?
The SEP provides a unique opportunity in that it provides a
somewhat constrained environment
Uniformity of format
Relatively small document base
Indeed, an ideal test best for more robust approaches to
If it can't work here, it can't work anywhere!
But is it scaleable?
Not clear that if it can work here, it can
SEP ontology as a "standard" reference ontology for
philosophical documents on the web.
"SEP compliant" documents?
The third question, briefly considered…
What do philosophers need to know about markup languages such as
XML and XHTML?
Hopefully not much.
Question is: How much do they need to know about representing
content in a form usable by the Semantic Web or an
Requires representation in some XML-based language like
RDFS or OWL.
Not clear how much *philosophers* will need to know about
this, but if philosophical content is going to get on the
web, this is the form it's gonna have to be in.
Nonetheless, it would be good at least for philosophers to
familiarize themselves with a variety of more specialized
languages that are being proposed as the basis for
representing content on the Web.
Final question, not considered at all:
What should philosophers be doing about developing common practices,
standards and tools for electronic publishing?
Last modified: Fri Mar 28 17:54:20 CST 2003