HPobSAM for modeling and analyzing IT Ecosystems – Through a case study

Abstract

The next generation of software systems includes systems composed of a large number of distributed, decentralized, autonomous, interacting, cooperating, organically grown, heterogeneous, and continually evolving subsystems, which we call IT Ecosystems. Clearly, we need novel models and approaches to design and develop such systems which can tackle the long-term evolution and complexity problems. In this paper, our framework to model IT-Ecosystms is a combination of centralized control and decentralized (self-organizing) approaches. We use a flexible formal model, HPobSAM, that supports both behavioral and structural adaptation/evolution. We use a detailed, close to real-life, case study of a smart airport to show how we can use HPobSAM in modeling, analyzing and developing an IT Ecosystem. We provide an executable formal specification of the model in Maude, and use LTL model checking and bounded state space search provided by Maude to analyze the model. We develop a prototype of our case study designed by HPobSAM using Java and Ponder2. Due to the complexity of the model, we can not check all properties at design time using Maude. We propose a new approach for run-time verification of our case study, and check different types of properties which we could not verify using model checking. As our model uses dynamic policies to control the behavior of systems which can be modified at runtime, it provides us a suitable capability to react to the property violation by modification of policies.

A Formal Model to Integrate Behavioral and Structural Adaptations in Self-adaptive Systems

“…In [13], the suitability of HPobSAM for modeling large-scale self-adaptive systems has been discussed, particularly, it was discussed how the hierarchical structure of this model to support centralized and decentralized adaptations, improves scalability. In [17], the authors refer to [13] and mention that how the hierarchical structure offers a form of controlled autonomy and balances agent autonomy and system controllability, for example to prevent unsafe situations caused by a selfish acting ATV.…”

“…HPobSAM is used in [13] to model a case study in the area of smart airports. In [13], we refer to an unpublished technical report for a complete description of HPobSAM.…”

“…HPobSAM is used in [13] to model a case study in the area of smart airports. In [13], we refer to an unpublished technical report for a complete description of HPobSAM. Here we present the description, architecture, and formal syntax and semantics of HPobSAM.…”

Adaptability checking in complex systems

“…In this section, we illustrate the features of our approach by means of an example adapted from [29]: a model of motion control of Autonomous Transport Vehicles (ATVs) in a smart airport. In this context, ATVs are responsible for the transport of passengers between stopovers like passenger entrances, check-in desks, departure gates, and plane parking positions.…”

“…Similarly to our structural and behavioural levels, the structure of a PobSAM model is built on multiple levels: the level of managed actors, the levels of autonomous managers and a view level, which acts as a sort of observation function over the state variables of the actors. Further, a recently published extension of PobSAM called HPobSAM [29], enables the hierarchical refinement of managed components. On the other hand, S[B] systems are based on the general formalism of state machines and enjoy the property that higher levels lead to higher-order structures: indeed, the S level can be interpreted as a second-order B level, since an S state identifies a set of stable B states and firing an S transition means performing an adaptation path, i.e.…”