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This presentation discusses the CellAK (Cell Assembly Kit) model, autopoiesis and a test case, and the enhanced CellAK that allows modeling autopoiesis. It explains the approach based on object-oriented paradigm and UML and ROOM visual formalisms, and how it can be implemented using different software development languages and tools.
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Combining Analysis and Synthesis in a Model of a Biological Cell Ken Webb & Tony White SAC ’04 March 17, 2004
Introduction In this presentation I will cover: • Some background • CellAK (Cell Assembly Kit) • Autopoiesis and SCL (example/test case) • Enhanced CellAK
Background • Started as exercise in bio-inspiration • Getting architectural ideas from biology that can be applied to developing complex computer systems • But there are also aspects of interest to members of cell modeling community • “Whole-cell modeling” (M. Tomita, E-CELL) • “Grand challenge of modeling multi-cellular animal” (D. Harel) • SBML compatible tools
Basic Rationale • In existing cell/biochem modeling tools • Each object is a separate act of human design • Using OO software development techniques • Process of building complex cell models is easier for humans (with reuse) • CellAK: example of such an OO system • Can have very large number of components • Paper accepted by journal BioSystems • Enhanced CellAK: introduced in this paper • Extends CellAK to allow it to model autopoiesis
CellAK • An approach to modeling and simulating cells, and other similar biological and non-biological entities. • Based on: • an object-oriented (OO) paradigm, • UML visual formalism, • ROOM visual formalism. • Prototype implemented using Rational Rose RealTime (RRT)
CellAK – some benefits • Scalable, through use of • Object instantiation from classes, • Multiplicity, • Chemical metaphor. • Easy to implement new behavior • If you know C/C++
CellAK – Multi-step Process CellAK incorporates a top-down process based on current practice in development of embedded and real-time systems. Add more detail at each step. • Identify entities, inheritance and containment hierarchies • Establish relationships between entities • Define entity behavior patterns • Implement detailed behavior • Validate Entities typically all from the biological domain.
4. Implement detailed behavior V * S v = ────── Km + S // Irreversible, 1 Substrate, 1 Product, 0 Activator, 0 Inhibitor, 0 Coenzyme case Irr_Sb1_Pr1_Ac0_In0_Co0: s = sm->molecule[gene->substrateId[0]].get(); nTimes = enzymeLevel * ((gene->substrateV * s) / (gene->substrateK + s)); sm->molecule[gene->substrateId[0]].dec( nTimes ); sm->molecule[gene->productId[0]].inc( nTimes ); break;
BioEntity • Our name for objects in a model of biological cells, or other similar complex reactive system. • May consist of any combination of: • Behavior • Fine-grained structure • Other bioEntities
Autopoiesis • “self-making” • All entities in an autopoietic system or network participate in the creation and continual transformation of other entities • Based on bottom-up synthesis rather than the top-down analysis of original CellAK.
Varela/McMullin SCL Model 3 types of randomly moving entities: • Catalyst CellAK: enzyme • Substrate CellAK: small molecule • Link CellAK: lipid • also Holes CellAK: water molecules
SCL-GRO source: [17] McMullin, B., and Gross, D. Towards the Implementation of Evolving Autopoietic Artificial Agents. http://www.eeng.dcu.ie/~alife/bmcm-ecal-2001/ bmcm-ecal-2001.pdf
CellAK version of SCL • CellAK was unable to model autopoietic systems such as in the SCL model. • An enhanced version of CellAK adds causal dependency to allow this. • In bioEntities that contain both behavior and fine-grained structure (FGS), the behavior may be at least partly dependent on details of that FGS.
CellAK – some limitations • Rigid Structure • Unable to evolve novel structure that can be incorporated into the running system. • Based on proprietary tool (RRT) • But, goal here is to present an approach that can be implemented using a variety of software development languages and tools.
Conclusions • CellAK can model biological systems with many thousands of components • OO/UML top-down decomposition (analysis) • Enhanced CellAK • Adds greater ability for bottom-up synthesis • Allows active objects to influence other active objects by effecting their constiuent parts • Can model autopoietic systems with lots of interdependencies