Chul-Joo Kim

Refining schizophrenia via graph reachability in esterel

Esterel is an imperative synchronous language for control-dominant reactive systems. The combination of imperative structures and the perfect synchrony hypothesis often result in schizophrenic statements. Previous studies explain the characteristics of schizophrenia as the instantaneous reentrance to block statements: local signal declarations and parallel statements. In practice, however, most instantly-reentered block statements do not cause any problems in Esterel compilation. In this paper, we refine schizophrenic problems in terms of signal emissions, and suggest an algorithm to detect harmful schizophrenia using reachability on control flow graphs (CFGs) in Esterel. Our algorithm performs well in analyzing practical programs. Moreover, it can be easily applied to existing compilers.

Building Blocks for Designing Future Multi-Device Interaction

The paradigm of the Internet of Things predicts that not only typical computing devices but also mundane objects will soon cooperate to achieve certain goals and communicate with users. In this paper we present a new way of designing multi-device interaction to accommodate diverse types of devices and relations among them. We first held a design workshop wherein participants created new multi-device interaction ideas by using device cards. We then analyzed the ideas in terms of the roles of devices, relations of devices with the user/environment, data type and data flow direction. Based on the findings, we identified 10 device roles and developed the corresponding diagram building blocks, each of which clearly visualizes its interaction partner and data flow characteristics. Our own investigation and additional design workshop showed that the building blocks along with device cards can help quickly create and improve multi-device interaction ideas with completeness.

Detection of harmful schizophrenic statements in esterel

In imperative synchronous languages, a statement is called schizophrenic if it is executed more than once in a single clock. When a schizophrenic statement is translated into a circuit, the circuit can behave abnormally because of the multiple executions. To solve the problems caused by schizophrenic statements, compilers duplicate the statements to avoid multiple executions. Esterel is an imperative synchronous language. Schizophrenic statements in Esterel are considered to occur due to the instantaneous reentrance of local signal declarations or parallel statements. However, if the corresponding circuit of a schizophrenic statement behaves normally, it is harmless and thus curing is not necessary. In this paper, we identify the conditions under which a schizophrenic statement of the Esterel program must be cured during circuit translation. We also propose an algorithm to detect schizophrenic statements that have to be cured on the control flow graphs (CFGs) of source codes. Our algorithm detects all schizophrenic statements that have to be cured and results in fewer false alarms on the benchmark programs used in the previous work. It is simple and based on the CFG of a program, implying that it can be merged into existing compilers easily.

A framework for dynamic inter-device task dispatch with eventual consistency

The Internet of Things (IoT) allows various things like mobile devices and electronic appliances to communicate over network. Inter-device apps can share data between devices and dispatch specific tasks to other devices to utilize their resources. The prevalence of JavaScript web apps that can run anywhere providing any browsers opens the gate to unanticipated interactions between devices. However, the current techniques require developers construct tasks to dispatch statically with strong consistency, and they do not provide any disciplined way to develop inter-device apps. In this paper, we propose IDTD (Inter-Device Task Dispatch), a framework that allows developers to construct and dispatch tasks into multiple devices dynamically with eventual consistency in a systematic manner. We provide a high-level architecture of IDTD, prove the soundness and eventual consistency of the framework, and present its practical usability.