1 4 January 2016 Architectural Design of a Distributed Application with Autonomic Quality Requirements DEAS St. Louis, USA, May 21 th, 2005 Danny Weyns, Kurt Schelfthout and Tom Holvoet University of Leuven, Belgium

2 4 January 2016 A challenging application AGV transportation system

3 4 January 2016 Traditional approach Centralized architecture oServer assigns transports to AGVs oServer plans routes etc. oVehicles are controlled by central server oLow level control AGVs is handled by E’nsor software Main non-functional properties oConfigurability (server is central configuration point) oPredictability (server manages execution of functionality)

4 4 January 2016 Aiming for new quality requirements AGVs are expected to be flexible and adapt their behavior autonomously with changing circumstances oExploit opportunities  Switch jobs when driving to a load when a more interesting transport pops up oAnticipate possible difficulties  Prefer jobs near to a battery charging station when battery needs to be charged in the near future oCope with particular situations  Choose the farthest load in the corridor

5 4 January 2016 Aiming for new quality requirements System is expected to deal with openness oAGVs leave/enter the system, e.g. for maintenance oCustomers intervene during execution of the system We investigate the feasibility of a decentralized architecture aiming to cope with these new quality requirements Joint R&D project between AgentWise research group and Egemin This talk: overview basic architecture of the system

6 4 January 2016 Overview Situated multiagent systems for the AGV transportation system A trace through the architectural design Round-up

7 4 January 2016 Situated multiagent systems What is a situated multiagent system (MAS)? oSet of autonomous entities (agents) explicitly situated in a shared structure (an environment) oAgents select actions “here and now”, they do not use long term planning (locality in time and space) oInteraction is at the core of problem solving (rather than individual capabilities) Decentralized control Adaptive behavior Collective behavior

8 4 January 2016 A situated MAS for the AGV transportation system Motivations for situated MAS Matching quality properties Situated MAS are a promising approach to build flexible, adaptable, open systems Matching characteristics  Locality in time and space: order assignment to idle AGV near to load, collision avoidance, etc.  Interaction at the core of problem solving: load manipulation, collision avoidance, etc.

9 4 January 2016 Reference architecture as a guidance for architectural design oEmbodies knowledge and experiences acquired during 4 years of research oServes as a reusable architectural design artifact oWe developed design guidelines for specific modules, e.g., decision making with free-flow architectures Reference architecture for situated MASs

10 4 January 2016 High-level overview of the reference architecture

11 4 January 2016 Overview Situated multiagent systems for the AGV transportation system A trace through the architectural design Round-up

12 4 January 2016 Deployment view of the decentralized architecture

13 4 January 2016 Top level module decomposition: situated MAS

14 4 January 2016 Module view of the environment: layers  Separate functionality, support reuse

15 4 January 2016 Virtual environment is a distributed entity

16 4 January 2016 Physical Environment

17 4 January 2016 Virtual Environment

18 4 January 2016 The virtual environment Offers a medium to agents to exchange information and coordinate their behavior Synchronizing state of the virtual environment oVirtual environment as software entity does not exist  Virtual environment is necessary distributed over the AGVs  ObjectPlaces middleware keeps state of local virtual environment synchronized with virtual environments of local AGVs

19 4 January 2016 AGV agents: data repository  Separation of concerns, loose coupling

20 4 January 2016 AGV agents: blackboard with sequential processing  Decision making at different levels of abstraction, separation of concerns  Feedback for flexible decision making

21 4 January 2016 Overview Situated multiagent systems for the AGV transportation system A trace through the architectural design Round-up

22 4 January 2016 The challenge continues Project status (after 1.2 of 2 years) o2 real AGVs manipulate loads, drive around and avoid collisions in an industrial test set-up (basics for deadlock prevention) oThe same for n AGvs in a simulated setup Current work oMethodological evaluation of software architecture: ATAM planned June oOrder assignment and deadlock avoidance Next challenges oExplore and validate flexibility, adaptability, scalability oGive guarantees about global behavior

23 4 January 2016 Lessons learned oWe learned the real value of our research by applying it in real-world application  We experienced what “application-driven research” is about oThe reference architecture serves as an excellent guidance for the architectural design oStakeholders not involved in the daily development tend to overestimate the agent metaphor