[[http://cadia.ru.is/wiki/public:t-720-atai:atai-16:main|T-720-ATAI-2016 Main]] 

=====T-720-ATAI-2016=====
====Lecture Notes, F-4	22.01.2016====
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====System Architecture====
|  What it is  | In CS: the organization of the software that implements a system.  \\ In AI: The total system that has direct and independent control of the behavior of an Agent via its sensors and effectors.   |
|  Why it's important  | The system architecture determines what kind of information processing can be done, and what the system as a whole is capable of in a particular Task-Environemnt.   |
|  Key concepts  | process types; process initiation; information storage; information flow.  |
|  Graph representation  | Common way to represent processes as nodes, information flow as edges.  |
|  Relation to AI  | The term "system" not only includes not only the processing components, the functions these implement, their input and output, and relationships, but also temporal aspects of the system's behavior as a whole. This is important in AI because any controller of an Agent is supposed to control it in such a way that its behavior can be classified as being "intelligent". But what are the necessary and sufficient components of that behavior set?   |
|  Intelligence is in part a systemic phenomenon  | Thought experiment: Take any system we deem intelligent, e.g. a 10-year old human, and isolate any of his/her skills and features. A machine that implements any //single// one of these is unlikely to seem worthy of being called "intelligent" (viz chess programs), without further qualification (e.g. "a limited expert in a sub-field").  |

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====Causal Structures====
|  {{ public:t-720-atai:coupled-systems.png }}   |
|  Nodes stand for identified causal factors, edges stand for the causal relationship between these.  \\ a. Sparsely coupled system; b. Densely coupled system; c. Tightly coupled system; d. Loosely coupled system; e. System with multi-variable couplings; f. Densely coupled system with mixed loose and tight, and multi-variable causal chains.  |

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====CS Architecture Building Blocks====
|  Pipes & filters  | Extension of functions. \\ Component: Each component has a set of inputs and a set of outputs. A component reads streams of data on its inputs and produces streams of data on its outputs, delivering a complete instance of the result in a standard order. \\ Pipes: Connectors in a system of such components transmit outputs of one filter to inputs of others.  |
|  Object-orientation  | Abstract compound data types with associated operations.  |
|  Event-based invocation  | Pre-defined event types trigger particular computation sequences in pre-defined ways.  |
|  Layered systems  | System is deliberately separated into layers, a layer being a grouping of one or more sub-functions.   |
|  Hierarchical systems  | System is deliberately organized into a hierarchy, where the position in the hierarchy represents one or more important (key system) parameters.  |
|   Blackboards   | System employs a common data store, accessible by more than a single a sub-process of the system (often all).  |
|  Hybrid architectures  | Take two or more of the above and mix together to suit your tastes.  |

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====Network Topologies====
|  Point-to-Point  | Dedicated connection between nodes, shared only by a node at each end.  |
|  Bus  | A message medium, shared by all nodes (or a subset).  |
|  Star  | Central node serves as a conduit, forwarding to others; full structure of nodes forming a kind of star.  |
|  Ring  | All nodes are connected to only two other nodes.  |
|  Mesh  | All nodes are connected to all other nodes (fully connected graph); can be relaxed to partially-connected graph.  |
|  Tree  | Node connections forms a hierarchical tree structure.  |
|  Pub-Sub  | In publish-subscribe architectures one or more "post offices" receive requests to get certain information from nodes.   |
|  reference  | [[https://en.wikipedia.org/wiki/Network_topology|Network topology on Wikipedia]]   |

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====Coordination Hierarchies====
|  {{ public:t-720-atai:coordinationhierarchies.png?500 }}   |
|  A functional hierarchy organizes the execution of tasks according to their functions. A product hierarchy organizes production in little units, each focused on a particular product. \\ Several types of markets exist - here two idealized versions are show, without and with brokers. De-centralized markets require more intelligence to be present in the nodes, which can be aleviated by brokers. Brokers, however, present weak points in the system: If you have a system with only 2 brokers mediating between processors and consumers/buyers, failure in these 2 points will render the system useless. \\ Notice that in a basic program written in C++ every single character is such a potential point of failure, which is why bugs are so common in standard software.  |
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====Methodology====
|   What it is   | The methods we use to study a phenomenon.  |
|   Why it's important   | Methodology directly influences the shape of our solution - our answers to scientific questions. For this reason, and equally importantly, it directly determines the speed with which we can make progress.  |
|   The main AI methodology   | AI never really had a proper methodology discussion as part of its mainstream scientific discourse. Only 2 or 3 approaches to AI can be properly called 'methodologies': BDI (belief, desire, intention), subsumption, decision theory. As a result AI inherited the run of the mill CS methodology/ies by default.  |

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====Constructionist Methodologies====
|  What it is  | A constructionist methodology requires an intelligent designer that manually (or via scripts) arranges selected //components// that together makes up a //system of parts// (read: architecture) that can act in particular ways. Examples: automobiles, telephone networks, computers, operating systems, the Internet, mobile phones, apps, etc.  |
|  Why it's important  | Virtually all methodologies we have for creating software are of this kind.   |
|   Fundamental CS methodology   | On the theory side, for the most part mathematical methodologies (not natural science). On the practical side, hand-coding programs and manual invention and implementation of algorithms. Systems creation in CS is co-owned by the field of engineering.   |
|   The main methodology/ies in CS   | Constructionist.  |
|  Constructionist AI  | Methodology for building //cognitive agents// that relies primarily on Constructionist methodologies.  |
|  Key Limitation  | Rests on the key assumption (on which CS - as a science - is built) that humans, or those with human-level intelligence, are the only ones that will create software systems.  |

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2016(c)K. R. Thórisson 
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