13 research outputs found
On a thermodynamic approach to biomolecular interaction networks
We explore the direct and inverse problem of thermodynamics in the context of
rule-based modelling. The direct problem can be concisely stated as obtaining
a set of rewriting rules and their rates from the description of the energy
landscape such that their asymptotic behaviour when t → ∞ coincide. To
tackle this problem, we describe an energy function as a finite set of connected
patterns P and an energy cost function e which associates real values to each of
these energy patterns.We use a finite set of reversible graph rewriting rules G to
define the qualitative dynamics by showing which transformations are possible.
Given G and P, we construct a finite set of rules Gp which i) has the same
qualitative transition system as G and ii) when equipped with rates according
to e, defines a continuous-time Markov chain that has detailed balance with
respect to the invariant probability distribution determined by the energy
function. The construction relies on a technique for rule refinement described
in earlier work and allows us to represent thermodynamically consistent
models of biochemical interaction networks in a concise manner.
The inverse problem, on the other hand, is to i) check whether a rule-based
model has an energy function that describes its asymptotic behaviour and
if so ii) obtain the energy function from the graph rewriting rules and their
rates. Although this problem is known to be undecidable in the general case,
we find two suitable subsets of Kappa, our rule-based modelling framework
of choice, were this question can be answer positively and the form of their
energy functions described analytically
Emergent Communities in Socio-Cognitive Networks
International audienceWe investigate a recent network model [13] which combines social and cognitive features. Each node in the social network holds a (possibly different) cognitive network that represent its beliefs. In this internal cognitive network a node denotes a concept and a link indicates whether the two linked concepts are taken to be of a similar or opposite nature. We show how these networks naturally organise into communities and use this to develop a method that detects communities in social networks. How they organise depends on the social structure and the ratio between the cognitive and social forces driving the propagation of beliefs
Emergent Communities in Socio-cognitive Networks
International audienceWe investigate a recent network model [13] which combines social and cognitive features. Each node in the social network holds a (possibly different) cognitive network that represent its beliefs. In this internal cognitive network a node denotes a concept and a link indicates whether the two linked concepts are taken to be of a similar or opposite nature. We show how these networks naturally organise into communities and use this to develop a method that detects communities in social networks. How they organise depends on the social structure and the ratio between the cognitive and social forces driving the propagation of beliefs
Reversible Sesqui-Pushout Rewriting
The paper proposes a variant of sesqui-pushout rewriting (SqPO) that allows one to develop the theory of nested application conditions (NACs) for arbitrary rule spans; this is a considerable generalisation compared with existing results for NACs, which only hold for linear rules (w.r.t. a suitable class of monos). Besides this main contribution, namely an adapted shifting construction for NACs, the paper presents a uniform commutativity result for a revised notion of independence that applies to arbitrary rules; these theorems hold in any category with (enough) stable pushouts and a class of monos rendering it weak adhesive HLR. To illustrate results and concepts, we use simple graphs, i.e. the category of binary endorelations and relation preserving functions, as it is a paradigmatic example of a category with stable pushouts; moreover, using regular monos to give semantics to NACs, we can shift NACs over arbitrary rule spans
Approximations for Stochastic Graph Rewriting
In this note we present a method to compute approximate descriptions of a class of stochastic systems. For the method to apply, the system must be presented as a Markov chain on a state space consisting in graphs or graph-like objects, and jumps must be described by transformations which follow a finite set of local rules
Coarse-graining the Dynamics of Ideal Branched Polymers
AbstractWe define a class of local stochastic rewrite rules on directed site trees. We give a compact presentation of (often countably infinite) coarse-grained differential systems describing the dynamics of these rules in the deterministic limit, and study in a simple case finite approximations based on truncations to a certain size. We show an application to the modelling of the dynamics of sugar polymers
Annotation of rule-based models with formal semantics to enable creation, analysis, reuse and visualization
Motivation: Biological systems are complex and challenging to model and therefore model reuse is highly desirable. To promote model reuse, models should include both information about the specifics of simulations and the underlying biology in the form of metadata. The availability of computationally tractable metadata is especially important for the effective automated interpretation and processing of models. Metadata are typically represented as machine-readable annotations which enhance programmatic access to information about models. Rule-based languages have emerged as a modelling framework to represent the complexity of biological systems. Annotation approaches have been widely used for reaction-based formalisms such as SBML. However, rule-based languages still lack a rich annotation framework to add semantic information, such as machine-readable descriptions, to the components of a model. Results: We present an annotation framework and guidelines for annotating rule-based models, encoded in the commonly used Kappa and BioNetGen languages. We adapt widely adopted annotation approaches to rule-based models. We initially propose a syntax to store machine-readable annotations and describe a mapping between rule-based modelling entities, such as agents and rules, and their annotations. We then describe an ontology to both annotate these models and capture the information contained therein, and demonstrate annotating these models using examples. Finally, we present a proof of concept tool for extracting annotations from a model that can be queried and analyzed in a uniform way. The uniform representation of the annotations can be used to facilitate the creation, analysis, reuse and visualization of rule-based models. Although examples are given, using specific implementations the proposed techniques can be applied to rule-based models in general. Availability and implementation: The annotation ontology for rule-based models can be found at http://purl.org/rbm/rbmo. The krdf tool and associated executable examples are available at http://purl.org/rbm/rbmo/krdf. Contact: or [email protected]