Dynamics of Galois Lattices The case of epistemic communities
Camille Roth & Paul Bourgine {roth,bourgine}@shs.polytechnique.fr CREA Centre de Recherche in Applied Epistemology CNRS / Ecole Polytechnique - Paris, France.
Sunbelt XXV, Redondo Beach, CA, USA - Feb 16-20th 2005
Objective Epistemic community taxonomy/dynamics • Describe communities of knowledge, in particular scientific communities, and their taxonomy: e.g. trends/subfields within a paradigm. • Epistemic community = group of agents who share a common set of topics, concerns, problems; who share a common goal of knowledge creation. (Haas (1992), Cowan et al. (2000), Dupouet et al. (2001)).
• Definition used here: « an epistemic community is the largest set of agents that share a given concept set»
Epistemic community taxonomy/dynamics
Formal framework Definitions • Consider the bipartite graph on R • Intent of an agent set S: all concepts used by every agent in S • Epistemic group: pair (S, C), where C is the intent of S. • Epistemic community (based on a concept set C): the maximal epistemic group based on C. • Dual notions • examples:
({A,B,C,E}, {McB}) ({B,C}, {McB,EmG})
Epistemic community taxonomy/dynamics
Formal framework Galois lattice • Good news: the extent of the intent of an agent set yields its epistemic community. • e.g.: from {C,D}, whose intent is {EmG}, whose extent is {B,C,D}, we get:
({B,C,D}, {EmG}) epistemic community • Pb: there communities…
may
be
many
such
Epistemic community taxonomy/dynamics
Formal framework Galois lattice
Epistemic community taxonomy/dynamics
Categorization Galois lattice • Hypotheses on scientific communities: they are structured (i) into fields, with common concerns, and (ii) hierarchically, through generalization/specialization relations. • We need a categorization method that allows overlap. • The Galois lattice is the ordered set of all epistemic communities (closed couples), provided with the natural partial order on sets.
Epistemic community taxonomy/dynamics
Categorization Galois lattice
« basic-level »
more general more specific
Epistemic community taxonomy/dynamics
Galois lattice Closed couple relevance & empirical results • Try to find a relevant level of generality/precision for the closed sets so that the lattice is manageable. • Given the assumptions, first criterion = fields = agent set size. • Very poor linguistic assumptions: small stop-word list, basic lemmatization, no contextual processing, no homonymy, synonymy, syllepsis, nominal groups • Computation of the lattice for a relation from MedLine data on zebrafish, 1990-1995 (6 years).
Galois lattice
Epistemic community taxonomy/dynamics
Empirical results
Galois lattice on « zebrafish » community: density of closed sets against extension sizes (author sets) as a proportion of agents of the whole community (200 authors) (1800 concepts)
Epistemic community taxonomy/dynamics
Galois lattice Empirical results • Large ECs: remarkable stylized fact of the data. • Partial real lattice successfully checked by domain experts:
Epistemic community taxonomy/dynamics
Galois lattice Selection -> Improve selection criteria, since “agent set size” is: (1) Over-selective: Large yet less significant sets. Additional criterion: Ratio between set and superset sizes. (2) Under-selective: Small yet significant sets. Additional criterion: Distance from the top.
Epistemic community taxonomy/dynamics
Galois lattice Selection and dynamics •
Three 6-year periods: Selection on 70 words.
90-95,
94-99
and
98-03.
•
Booming community: from 1000 authors at the end of 1995, to 9700 by 2004 (and 3700 in 1999).
•
Selection criteria:
(1) catch large communities: Size/distance *#attributes (2) catch isolated communities: Size/distance *number of sons
Epistemic community taxonomy/dynamics
Dynamic Partial Lattice 90-95
98-03
thanks…
to be continued on http://camille.roth.free.fr
