Copyright © 2005 Coolheads Consulting Coolheads Consulting Bottom-up Semantic Integration Michel Biezunski Steven R. Newcomb Coolheads Consulting Collaborative Expedition Workshop #38, February 22, 2005 National Science Foundation, Arlington VA

Copyright © 2005 Coolheads Consulting  The Title of this Expedition Workshop is: How big is each community that will make commitments together? Semantic Conflict Mapping and Enablement: Making Commitments Together

Copyright © 2005 Coolheads Consulting  Some lessons from history… No semantic universe is big enough for everything. The siren songs of Esperanto-like one-size-fits-all solutions lead to failure. Don’t listen to them. There is no ultimate top level at which to anchor all semantics, nor can one be manufactured. (It’s a very old lesson. The Babel myth can be seen as the earliest literary treatment of it.)

Copyright © 2005 Coolheads Consulting  Limits on semantic territory The larger the semantic territory, the harder it is to police its consistency (top down). Inclusive semantic territories are impossible to police. When traveling through unpoliceable semantic territories, it’s wise to hire tour guides and bodyguards (bottom up). Don’t expect all the natives to behave predictably, and, when they don’t, don’t expect help from the semantic police. There aren’t any.

Copyright © 2005 Coolheads Consulting  Less is more The larger the semantic territory covered by an ontology, the fewer people will actually use it. When describing a semantic universe from the top down, there’s a limit to how high you can start, and still succeed. Above there, bottom-up is the only alternative.

Copyright © 2005 Coolheads Consulting  But... Nevertheless, collaboration requires semantic consistency. When knowledge interchange fails, the finger of blame must be pointable. Communities really must “make [ontological] commitments together” in order to achieve any consistency at all – in order to exhibit any kind of community behavior.

Copyright © 2005 Coolheads Consulting  Semantic Interoperability vs. Integration When two knowledge bases are semantically interoperable, it means that if both make the same statement, the same inferences are licensed by that statement. When two knowledge bases are semantically integrated, whenever they each have proxies for the same subject, the resulting single knowledge base has only one proxy for the same subject, and that proxy reflects everything that each knowledge base knew about it.

Copyright © 2005 Coolheads Consulting  Cost as a function of semantic scope Scope of semantics Cost of semantic interoperability Cost of semantic integration $

Copyright © 2005 Coolheads Consulting  Smaller semantic universes: Police reports IRS tax publications Environmental impact statements Drug safety reports Budgets Etc.

Copyright © 2005 Coolheads Consulting  Semantic Integration: The Underlying Perspective Thing Subject Interpretation Perspective View Semantic Integration: For each subject, a single perspective on all the information that's relevant to that subject.

Copyright © 2005 Coolheads Consulting  Thing vs. Subject A thing exists in the universe, independently of any observer. A subject is an understanding of a thing.

Copyright © 2005 Coolheads Consulting  Subject  A subject is pure meaning and can't be reduced to: An address where it can be located. The words used to designate it (its name or other identifier). The words used to speak about it (e.g., its description).  A subject (i.e., an understanding) has features but those too are only subjects (i.e. understandings). Even within the mind of a single person at a single moment, the understandings do not form a consistent system.  Democracy of the “multitude”.  “Am I inconsistent? Of course I am inconsistent! I contain multitudes!” (Walt Whitman)  There is no limit to the diversity of subjects. All understandings are equal.

Copyright © 2005 Coolheads Consulting  Interpretation Understandings -> Expressions  An interpretation is an appearance of a subject in the world of expressions. It's an expression.  A given subject can be expressed many different ways. Expressions -> Understandings  The way a subject is expressed influences the ways it is understood.  No subject can be understood in the absence of a context consisting of other understandings.

Copyright © 2005 Coolheads Consulting  Proxy Proxies are expressions that represent subjects. Every proxy represents exactly one subject. A proxy can only be understood as a proxy in the light of a perspective. A proxy is a set of properties (label-value pairs) For example, “name” is a possible property of a proxy.

Copyright © 2005 Coolheads Consulting  Perspective A perspective is a set of rules to which proxies must comply. Rules for recognizing subject proxies. Rules for recognizing the subjects of subject proxies. Rules for combining 2 or more proxies that have the same subject. Ontologies rarely make these ontological commitments. They don't tell us what these rules are. Several perspectives are possible over the same set of information resources.

Copyright © 2005 Coolheads Consulting  View A view is a bunch of proxies treated as a unit. A perspective governs how views are specified and interpreted. For example, a perspective can specify that two proxies are to be merged if the value of their name property is identical. another perspective can be that two proxies only merge if both their name property and their name type property match. Washington/State not merged with Washington/Person or Washington/City

Copyright © 2005 Coolheads Consulting  How does Semantic Integration Work? Semantic Integration makes heterogeneity appear to be orderly and consistent: “E Pluribus Unum”. Any perspective and view within that perspective can be defined, but the information to be “viewed” does not have to be specially prepared. Computers can help. Defining what can be automated and what needs human input is part of the design. Maintaining an integrated view of information when contributing sources evolve is an important dimension.