SCEC Ontology Description

The SCEC Ontology contains information about general seismological
terms, some data about faults (as an example), and information about
probabilistic seismic hazard analysis (PSHA) models.

The general seismological terms cover such concepts and relationships
as SITE, a location with relations such as LATITUDE-OF, VS30-OF-SOIL,
BASIN-DEPTH-2.5, etc.  There are also descriptions of a FAULT, which
is a SURFACE, which is a 2D-OBJECT embedded in a 3D space.  Various
fault types have been defined in terms of underlying physical
measurements such as dip, rake and slip.  The basis for the
terminology was supplied in meetings by Tom Jordan and Ned Field.  The
conventions for these measurements were chosen to follow the scheme
used in Aki & Richards _Theoretical Seismology_.

The ontology sources are (currently) three PowerLoom files:

    PL:kbs;scec;seismology.plm
    PL:kbs;scec;models.plm
    PL:kbs;scec;faults.plm

The ontology is structured into different reasoning modules (with
inheritance) that exhibit the following structure:

    PL-KERNEL-KB         Builtin to PowerLoom
       UNITS-KB          Support for units and dimensions
       SEISMOLOGY        General Seismology terms
         MODELS          Specific model terms and facts
           WORK          Scratch module for reasoning
         FAULTS          Specific fault facts

There is inheritance from the parents, and all of the modules inherit
the UNITS-KB module.

We anticipate that the organization of the models part of the module
hierarchy will change to accomodate scaling.  In the new scheme, each
PSHA model will have its own context and scratch module associated
with it.  This change will necessitate some changes to the methods
used to access the information in the ontology, but it will also make
adding new models a more incremental process and thus simpler.