Foundations of Knowledge Management Categorization & Formal Concept Analysis

Transcription

1 Foundations of Knowledge Management Categorization & How can concepts be formalized? Markus Strohmaier Univ. Ass. / Assistant Professor Knowledge Management Institute Graz University of Technology, Austria markus.strohmaier@tugraz.at web: 1

2 Slides in part based on Gerd Stumme Course at Otto-von-Guericke Universität Magdeburg / Summer Term 2003 ECML PKDD Tutorial Rudolf Wille as Mathematical Theory of Concepts and Concept Hierarchies, In, Eds B. Ganter et al., LNAI 3626, pp1-33, (2005) Further Literature: (Ganter / Stumme) 2

3 Overview Today s Agenda: Categorization & Formal Context Formal Concepts Formal Concept Lattices FCA Implications Constructing Concept Lattices 3

4 Categorization [Mervis Rosch 1981] Intension (Meaning) The specification of those qualities that a thing must have to be a member of the class Extension (the objects in the class) Things that have those qualities 4

5 Categorization [Mervis Rosch 1981] Six salient problems: Arbitrariness of categories. Are there any a priori reasons for dividing objects into categories, or is this division initially arbitrary? Equivalence of category members. Are all category members equally representative of the category as has often been assumed? Determinacy of category membership and representation. Are categories specified by necessary and sufficient conditions for membership? Are boundaries of categories well defined? The nature of abstraction. How much abstraction is required--that is, do we need only memory for individual exemplars to account for categorization? Or, at the other extreme, are higher-order abstractions of general knowledge, beyond the individual categories, necessary? Decomposability of categories into elements. Does a reasonable explanation of objects consist in their decomposition into elementary qualities? The nature of attributes. What are the characteristics of these "attributes into which categories are to be decomposed? 5

6 Terminology ISO 704: Terminology Work: Principles and methods DIN 2330: Begriffe und Ihre Benennungen Representation level Name Definition Concept level Concept attribute a attribute b attribute c Object level Object 1 property A property B property C Object 2 property A property B property C Object 3 property A property B property C 6

7 [Wille 2005] Models concepts as units of thought. A concept is constituted by its: Extension: consists of all objects belonging to a concept Intension: consists of all attributes common to all those objects Concepts live in relationships with many other concepts where the sub-concept-superconcept-relation plays a prominent role. 7

8 Formal context: [Wille 2005] A Formal Context is a tripel (G, M, I) for which G and M are sets while I is a binary relation between G and M. Formal Concept: A formal concept of a formal context K := (G,M, I) is defined as a pair (A,B) with and A = B, and B = A ; A and B are called the extent and the intent of the formal concept (A,B), respectively. 8

9 Running Example: Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, Ich möchte nur darauf hinweisen, daß es eine Zeit gab, in der man die Ähnlichkeit der Empfindungen zur Basis der Kategorisierung von Pflanze und Tier gemacht hat. Man denke [...] an die frühen Taxonomien des Ulisse Aldrovandi aus dem 16. Jahrhundert, der die scheußlichen Tiere (die Spinnen, Molche und Schlagen) und die Schönheiten (die Leoparden, die Adler usw.) zu eigenen Gruppen [von Lebewesen] zusammenfasste. Heinz von Foerster, Wahrheit ist die Erfindung eines Lügners, Page 22/23 [Mervis Rosch 1981] 9

10 Def.: A formal context is a tripel (G,M,I), where G is a set of objects, M is a set of attributes and I is a relation between G and M. Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, (g,m) I is read as object g has attribute m. 10

11 Derivation Operators Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, A G, B M (A Extent, B Intent) all attributes shared by all objects of A all objects having all attributes of B A 1 A 1 The two derivation operators satisfy the follwing 3 conditions: 11

12 Def.: A formal concept is a pair (A,B), with A G, B M A =B and B = A Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, all attributes shared by all objects of A all objects having all attributes of B Intent Set A is called the extent (a set of objects) Set B is called the intent (a set of attributes) Extent Of the formal concept (A,B) 12

13 Sub/Superconcept Relation Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, A G, B M all attributes shared by all objects of A all objects having all attributes of B A 2 A 1 A 2 A 1 The orange concept is a subconcept of the blue one, since its extent is contained in the blue one. (equivalent to the blue intent is contained in the orange one) 13

14 Galois Lattices / Galois Connections 14

15 Concept Lattices Concept Lattices (cf. Galois Lattices) Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, A 2 A 1 A 2 A 1 A1 Extent Intent A2 Formal Concept A1 (A1, A1 ) The set of objects that are yellow, sweet and smooth 15

16 Concept Lattices Concept Lattices (cf. Galois Lattices) Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, A 1 Intent (Attributes) Extent (Objects) A1 A 1 16

17 Concept Lattices Def.: The concept lattice of a formal context (G,M,I) is the set of all formal concepts of (G,M,I), together with the partial order The concept lattice is denoted by B(G,M,I). Theorem: The concept lattice is a lattice, i.e. for two concepts (A 1,B 1 ) and (A 2,B 2 ), there is always a greatest common subconcept and a least common superconcept 17

18 Greatest Common Subconcept Which objects share the attributes smooth and red and sour? A: Grapes, Apples greatest common subconcept (infimum) a greatest common subconcept and a least common superconcept 18

19 Least Common Superconcept Which attributes share the objects strawberries and lemon? A: Bumpy, round least common superconcept (supremum) a greatest common subconcept and a least common superconcept 19

20 Implications Def.: An implication A -> B holds in a context (G, M, I) if every object intent respects A ->B, i.e. if each object that has all the attributes in A also has all the attributes in B. Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, We also say A->B is an implication of (G,M,I). A B B A 20

21 Object count Implications Taste: Sweet/Sour, Shape: Round/Long/, Color: Red/Yellow/.., Texture: Smooth/Bumpy, 21

22 Implications: Applications / AOL Search Query Logs 22

23 Applications / Goal Tagging Implications: 23

24 Applications / Bugs - Bugzilla Implications: 24

25 FCA / Scaling Transforming many-valued into single valued contexts Many-valued contexts Color Shape Taste Texture Apple Lemon Red/ green/ yellow Yellow Round Round Sweet/ sour sour Smooth Bumpy What hasn t been mentioned yet Banana Yellow Long Sweet Smooth Strawberries Red Round Sweet Bumpy Grapes Red/ green Round Sweet/ sour Smooth Pear Yellow Long Sweet Smooth Via Scales S 1 red green yellow Color Shape Taste Texture red green yellow 25

26 Constructing Lattices 26

27 A Naive Approach: Lattice Construction Algorithms Ganter / Stumme

28 Lattice Construction Algorithms Example: (Formal Concepts) Ganter / Stumme

29 A Naive Approach: Lattice Construction Algorithms Ganter / Stumme

30 Lattice Construction Algorithms Example: ({T 2,T 7 },{e}) <= ({T 1,T 2,T 3,T 4,T 5,T 6,T 7 },{0}) Ganter / Stumme 2003 ({0},{a,b,c,d,e}) <= ({T 4 },{a,b,c}) a circle for a concept is always positioned higher than all circles for its proper subconcepts. Ganter / Stumme

31 Lattice Construction Algorithms Example ctd : Ganter / Stumme

32 Tools: E.g. ConExp Networks.tb JaLaBa Further Information FCA Homepage 32

33 ConExp 33

34 Bonus Task Define a Formal Context, for which G >=10, M >=10 and I ~ G + M Use Conexp to Name all elements of G and M (choose plausible G and M) Represent your formal context (choose plausible I) Draw the Concept Lattice Calculate Implications (there should be at least one implication with f>3) Submit The ConExp.cex file that contains your context and the layouted(!) lattice Name the Conexp File using the following Syntax: GWM08-BT1-YOURMATR-YOURLASTNAME.cex To me via using subject [GWM08-BT1-YOURMATR] before the beginning of next week s class 34

35 Any questions? See you next week! 35