# Info on Pittsburgh Bridges Data Base

    1. Title: Pittsburgh bridges

    2. Sources:
       -- Yoram Reich & Steven J. Fenves
          Department of Civil Engineering
          and
          Engineering Design Research Center
          Carnegie Mellon University
          Pittsburgh, PA 15213

          Compiled from various sources.

       -- Donor: Yoram Reich (yoram.reich@cs.cmu.edu)
       -- Date: 1 August 1990

    3. Past Usage:

       -- Reich & Fenves (1989). Incremental Learning for Capturing Design
          Expertise. Technical Report: EDRC 12-34-89, Engineering Design
          Research Center, Carnegie Mellon University, Pittsburgh, PA.
          -- Qualitative results and runs with original ordering of examples.
             using COBWEB.

       -- Reich (1989). Converging to ``Ideal'' Design Knowledge by Learning,
          Proceedings of the First International Workshop on Formal Methods in
          Engineering Design, pp: 330-349, Colorado Springs, CO, January 1990.
          -- Describes a new design method with Bridger (variant of COBWEB) using
    	 this domain. (Also an EDRC report: 12-35-89)

       -- Reich (1989) Combining Nominal and Continuous Properties in an
          Incremental Learning System for Design. Technical Report: EDRC 12-33-89.
          -- Comparison of performance of Bridger when running on both versions
    	 (V1 and V2) of the database

       -- Reich (1989) Incremental Concept Formation with Mixed Property Types
          Unpublished Manuscript.
          -- Results using 10 random 10-fold cross-validation test with Bridger
    	 (relative error rate):
    	 Version V1 of the database:
    	 MATERIAL 18.4%, REL-L 38.7%, SPAN 42.7%, T-OR-D 14.7%, TYPE 47.6%.
    	 Version V2 of the database:
    	 MATERIAL 24.2%, REL-L 41.7%, SPAN 39.9%, T-OR-D 14.7%, TYPE 56.5%.

       -- Quinlan (1989) Personal communication.
          -- Results of a 10-fold cross-validation test with C4.5, and with
             a separate decision tree for each design property obtained the
    	 following error rates on version V1 of the database:
    	 MATERIAL 15%, REL-L 32%, SPAN 32%, T-OR-D 15%, TYPE 44%.

    4. Number of instances: 108

    5. Relevant Information:

       There are two versions to the database:
          V1 contains the original examples and
          V2 contains descriptions after discretizing numeric properties.

       There are no ``classes'' in the domain. Rather this is a DESIGN domain where
       5 properties (design description) need to be predicted based on 7
       specification properties.

    6. Number of Attributes: 13: 7 specifications, 5 design description, and 1
       identifier (not used for the classification)

    7. Attribute Information:

       The type field state whether a property is continuous/integer (c)
    						      or nominal (n).
       For properties with c,n type, the range of continuous numbers is given
       first and the possible values of the nominal follow the semi-colon.

           name     type    possible values		comments
       ------------------------------------------------------------------------
       1.  IDENTIF	-	-			identifier of the examples
       2.  RIVER	n	A, M, O
       3.  LOCATION	n       1 to 52
       4.  ERECTED	c,n	1818-1986 ; CRAFTS, EMERGING, MATURE, MODERN
       5.  PURPOSE	n	WALK, AQUEDUCT, RR, HIGHWAY
       6.  LENGTH	c,n	804-4558 ; SHORT, MEDIUM, LONG
       7.  LANES	c,n	1, 2, 4, 6 ; 1, 2, 4, 6
       8.  CLEAR-G	n	N, G
       9.  T-OR-D	n	THROUGH, DECK
       10. MATERIAL	n	WOOD, IRON, STEEL
       11. SPAN	n	SHORT, MEDUIM, LONG
       12. REL-L	n	S, S-F, F
       13. TYPE	n	WOOD, SUSPEN, SIMPLE-T, ARCH, CANTILEV, CONT-T

    8. More complicated attributes:

       One can use a hierarchical structure for the Type property. There are two
       options.

    	option 1 (use examples without modification)
            --------

    			Type
    	     /      /	     \     \
    	   /       /	      \	     \
    	wood	suspen		arch	truss
    				       /  |    \
    				     /    |      \
    				cantilev  cont-t   simple

    	option 2 (requires changes in the Type property - specified bellow)
    	--------

    				Type

    		 /     	/        |	    	    \
    	   	/     /	         |   		     \
    	    wood   suspen	arch		      truss
    				/ \	    	   /  |  \    \
    			      /	    \	  	 /    |   \	\
    			tied-a    not-tied  cantilev cont-t simple arch-t

    	Change the Type  property of the following examples (in both V1 and V2):
    		E28   ->  arch-t
    		E91,E90,E84,E83,E73  -> tied-a
    		E97,E78,E77,E75,E66,E64,E43  -> not-tied

    9. Missing Attribute Values:
       Attribute #: 	# instances with missing values:
        2			 1
        6			27
        7			16
        8			 2
        9			 6
       10			 2
       11			16
       12			 5
       13			 3