Yeongbok Choe

δ-calculus: Process Algebra to Model Secure Movements of Distributed Mobile Processes in Real-time Business Applications

Some process algebras were applied to enterprise business modelling for formal specification and verification. However the algebras mostly dealt with stationary cases but the distributed and mobile. calculus and mobile ambient can be considered for the distributed and mobile, especially to represent the movements of distributed real-time business processes. However there are some limitations to model the movements: 1) -calculus passes the name of port for indirect movements, and 2) mobile ambient uses ambient to synchronize asynchronous movements forcefully. As a solution to the limitations, this paper presents new process algebra, called -calculus, to specify direct and synchronous movements of business processes over geo-temporal business space, where a process can be nested in another process, and whose configuration is changed by the movements. Any violation of safety or security of the systems caused by the movements can be detected and prevented by the properties of the movements: synchrony, priority and deadline. It means that any movement must get the proper permission with the required priority in time. In the enterprise modelling, it will be critical to adapt this kind of concept for business safety and security. A tool, called SAVE, was developed on ADOxx meta-modelling platform to demonstrate the concept.

A Reduction Method for Process and System Complexity with Conjunctive and Complement Choices in a Process Algebra

This paper introduces new notion of conjunctive and complement choices in process algebra, which reduces significant process and system complexity for distributed mobile real-time system during specification and analysis. The complement choice implies that two processes make cohesive choices for each other at its own choice operation. The conjunctive choice implies choice dependency among consecutive choice operations in a process. The conjunctive choice reduces process complexity exponentially by the degree of the choice dependencies. The complement choice also reduces system complexity exponentially by the degree of the choice dependencies. Consequently, the approach makes the specification and analysis of the systems much easier since the complexity is reduces significantly. This notion is implemented in a process algebra, called δ-calculus. The efficiency and effectiveness are demonstrated with an example in a tool for the algebra, called SAVE, which is developed on ADOxx platform.

SAVE: An Environment for Visual Specification and Verification of IoT

This paper presents a visual environment, called SAVE, to model IoT systems with dynamic and static properties. Firstly, the dynamic properties, such as operational requirements, of the systems are specified with a process algebra, called δ-Calculus, and, secondly the static properties, such as safety requirements, of the systems are specified with a first-order logic, called GTS Logic. Once specifications are done, the static properties are verified on the dynamic properties by checking whether or not the static properties are valid for the simulation of the systems based on the dynamic properties. SAVE provides a set of visual tools to specify both dynamic and static properties of the systems, simulate the systems based on the dynamic properties, and to verify the static properties on the dynamic properties from the simulation. SAVE is developed on the ADOxx meta-modeling platform. It can be considered one of the most innovative visual tools to model IoT systems for both dynamic and static properties of the systems and to verify the validity of the static properties on the dynamic properties.

A Lattice Model to Verify Behavioral Equivalences

This paper presents a new model to verify behavioral equivalences based on behavior ontology. In the ontology, actions among processes or tasks are defined as interaction and movement, and, further, behaviors are defined as a sequence of such interactions and/or movements. Since some interactions and movements among the behaviors are overlapped, the behaviors are organized in a lattice structure, called, n:2-Lattice. Compared to other lattices, the lattice has special properties of multiple joins and meets. The property allows polymorphic interpretations of behaviors for equivalence, based on degree of abstraction. It guarantees abstraction of the exponential and nondeterministic complexity of behaviors into polynomial complexity. The ontology can be considered as one of the unique and innovative structure to represent behavioral equivalences.

Algebraic Method to Model Secure IoT

Process algebra can be considered to be one of the best methods to model IoT systems since it can represent the main properties of things in the systems: communication, movements, deadlines, etc. The best known algebras are π-calculus and mobile ambient. However, there are some limitations to model the different types of movements of the things with secure requirements. π-calculus passes the name of ports for indirect movements unrealistically, and mobile ambient uses ambient to synchronize asynchronous movements forcefully and unnaturally. This paper presents new process algebra, called δ-calculus, to model the different types of such synchronous movements for the things in IoT over some target geographical space. A process can be nested in another process, and their configuration will be changed by these movements. Any violation of the secure movements can be detected and prevented by the properties of the movements: synchrony, priority and deadline. To demonstrate the feasibility, a tool, called SAVE, was developed on the ADOxx metamodeling platform with an emergency medical system, which is one of the best suitable application domains for IoT.

An Abstraction Method of Behaviors for Process Algebra

In CCS, Milner defined the notion of Strong and Weak Bisimulations for behavioral equivalence between two processes or systems. However the notion has not been studied further in the perspective of abstraction for such behaviors in process algebra. In some sense, weak bisimulation could be interpreted as a kind of behavior equivalence between two processes at the certain degree of abstraction, based on observability. Here we noticed the possibility of representing such observable behaviors with a certain structure of abstraction and verify a number of behavioral equivalences in the structure. In the paper, such possibility has been realized with a new concept of Behavior Ontology. In the ontology, actions can be defined as an interaction between two processes or systems, and, further, behaviors can be defined as a sequence of such actions. Since some actions between the behaviors can be overlapped in some structural way, the behaviors can be organized in a lattice structure, namely, Behavior Lattice. Consequently, the lattice reveals certain levels of observability of the behaviors, based on degree of abstraction. From the lattice, a strong bisimulation and its weak bisimulations can be detected visually. The comparative study shows that the ontology is very effective and efficient for representing such abstract behaviors and verifying strong and weak bisimulations in a lattice structure. The ontology can be considered as one of the unique and innovative structure to represent such behaviors in a hierarchical structure of abstraction.

A Process Algebra for Modeling Secure Movements of Distributed Mobile Processes

Some process algebras were applied to enterprise business modelling for formal specification and verification. -calculus and mobile ambient can be considered for the distributed and mobile, especially to represent the movements of distributed real-time business processes. However there are some limitations to model the movements: 1) -calculus passes the name of port for indirect movements, and 2) mobile ambient uses ambient to synchronize asynchronous movements forcefully. As a solution to the limitations, this paper presents a new process algebra, called -calculus, to specify direct and synchronous movements of business processes over geo-temporal space. Any violation of safety or security of the systems caused by the movements can be indicated by the properties of the movements: synchrony, priority and deadline. A tool, called SAVE, was developed on ADOxx metamodelling platform to demonstrate the concept.

Meta-Modeling to Detect Attack Behavior for Security

This paper presents a new method to detect attack patterns in security-critical systems, based on a new notion of Behavior Ontology. Generally security-critical systems are large and complex, and they are subject to be attacked in every possible way. Therefore it is very complicated to detect various attacks through a semantic structure designed to detect such attacks. This paper handles the complication with Behavior Ontology, where patterns of attacks in the systems are defined as a sequences of actions on the class ontology of the systems. We define the patterns of attacks as sequences of actions, and the attack patterns can then be abstracted in a hierarchical order, forming a lattice, based on the inclusion relations. Once the behavior ontology for the attack patterns is defined, the attacks in the target systems can be detected both semantically and hierarchically in the ontology structure. When compared to other attack models, the behavior ontology analysis proposed in this paper is found to be very effective and efficient in terms of time and space.