Information Flow

Julio Ostalé 
 Incorporated contributions
Ostalé (3/2010)
 Usage domain
transdiciplinary, semantics, situation theory
concept, metaphor
flux d'information
 German Informationsfluss
[Understandable but with some grammatical missteps]

  1. Information and information flow
  2. Defining information flow

There is no standard definition of "information flow", and neither there is of "information". Nevertheless, in ordinary life we seem to be in agreement with the meanings of information and information flow. A major problem is to know whether information flow is a concept or a metaphor. Here we are going to assume it is a concept.
While the concept of information is quite difficult to grasp, a definition of information flow in terms of information should not be that hard. Therefore, in this entry we propose an informal definition of information flow from the starting point of some elementary concepts in a well-established theory of semantic information: situation theory (Barwise and Perry 1983; Barwise 1989; Devlin 1991).
1. Information and information flow
Situation theory distinguishes between information and information flow (Devlin 1991: 142-144). The basic assumption is that information is abstract and can be used for classifying concrete states of affairs. On this assumption is built up the following distinction:
  • There is information about a state of affairs as long as we can classify it by means of abstract states, such as vectors, time periods or logical formulae. We then say that the state of affairs supports certain information. Example: we have information about the waitress in that we know that his hands are muddy.
  • There is flow of information from one state of affairs to another as long as some way of classifying the first one indicates some way of classifying the second. Then we say that the first state of affairs carries information about the second one. Example: the fact that the waitress' hands are muddy carries the information that my plate is possibly muddy.

In theories prior to situation theory this distinction was not always taken into account. Neither it is clearly stated in recent proposals like that of Floridi (2005). On the other hand, whenever the flow of information is on the focus two typical problems arise immediately:

  • Is it required the existence of agents for the flow of information to take place? Usually this question is answered in an affirmative manner. Situation theory gives for granted their existence in despite of some occasional debate on this matter. Channel theory (Barwise and Seligman 1997), on the contrary, doesn't mention agents very frequently. Dretske (1981) is not completely clear. On the one hand he defines the flow of information through the notion of an external observer: "A state of affairs contains information about X to just that extent of which a suitable placed observer could learn something about X by consulting it" (Dretske 1981: 45); on the other hand, he states that information is an agent-independent phenomenon. Floridi (2005) distinguishes between semantic information (which is agent-dependent) and environmental information (which is agent-independent).
  • How to explain the properties of the flow of information? Pérez-Montoro (2007) offers a comprehensive discussion of both these properties: relativity (the same state of affairs might carry different pieces of information to different agents), and fallibility (sometimes a state of affairs do not carry the information it is supposed to carry). Almost any author tries to explain those properties, which in turn exhibit different names as well as diverse formulations.
2. Defining information flow
Now then, neither in situation theory nor in further theories information flow is defined as such. It is only said that there is flow of information whenever some states of affairs carry information about each other. A definition of information flow must be therefore based on the concept of information.
If we call "distributed system" to any collection of states of affairs that are able of carrying information about each other (Barwise and Seligman 1997), and we call "information transfer" to the fact that -with respect to a distributed system- a state of affairs actually informs about another one, then we can define the flow of information within a distributed system as the class of all its information transfers with respect to certain analysis of the system as well as certain period of time. This definition has the advantage of conforming with common sense and with some basic yet fundamental concepts of situation theory.
  • BARWISE, J. (1989). The situation in logic. Stanford: CSLI Publications.
  • BARWISE, J. & PERRY, J. (1983). Situations and Attitudes. Cambridge, MA: Bradford Books / The MIT Press.
  • BARWISE, J. & SELIGMAN, J. (1997). Information Flow. The Logic of Distributed Systems. Cambridge: Cambridge University Press.
  • DEVLIN, K. (1991). Logic and Information. Cambridge: Cambridge University Press.
  • DRETSKE, F. (1981). Knowledge and the Flow of Information. Oxford: Basil Blackwell.
  • FLORIDI, L. (2005). Semantic Conceptions of Information. [Online]. Stanford: Stanford Encyclopedia of Philosophy. [En línea] <> [Consulted: 08/11/2009].
  • PÉREZ-MONTORO, M. (2007). The Phenomenon of Information. A Conceptual Approach to Information Flow. Medford, NJ: The Scarecrow Press, Inc.
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