Qiusong Yang

A cut-off approach for bounded verification of parameterized systems

The features in multi-threaded programs, such as recursion, dynamic creation and communication, pose a great challenge to formal verification. A widely adopted strategy is to verify tentatively a system with a smaller size, by limiting the depth of recursion or the number of replicated processes, to find errors without ensuring the full correctness. The model checking of parameterized systems, a parametric infinite family of systems, is to decide if a property holds in every size instance. There has been a quest for finding cut-offs for the verification of parameterized systems. The basic idea is to find a cut-off on the number of replicated processes or on the maximum length of paths needed to prove a property, standing a chance of improving verification efficiency substantially if one can come up with small or modest cut-offs. In this paper, a novel approach, called Forward Bounded Reachability Analysis (FBRA), based upon the cut-off on the maximum lengths of paths is proposed for the verification of parameterized systems. Experimental results show that verification efficiency has been significantly improved as a result of the introduction of our new cut-offs.

Value-Based Multiple Software Projects Scheduling with Genetic Algorithm

Scheduling human resources to multiple projects under various resource requirements, constraints and value objectives is a key problem that many software organizations struggle with. This paper gives a value-based human resource scheduling method among multiple software projects by using a genetic algorithm. The method synthesizes the constraints such as those of schedule and cost as well as the value objectives among different projects, and also the construction of comprehensive value function for evaluating the results of human resource scheduling. Under the guidance of value function, capable human resources can be scheduled for project activities by using the genetic algorithm and make the near-maximum value for organizations. Case study and the simulation results show that the method can perform the scheduling and reflect the value objectives of different projects effectively, and the results provide a concrete decision support for project managers.

An algebraic approach for managing inconsistencies in software processes

To produce quality software and evolve them in an economic and timely fashion, enactable software process models are used for regulating development activities with the support of Process-Centered Software Engineering Environments (PCSEEs). However, due to the dynamically changing development environment, the developers do not always follow the process model in presence of unforeseen situations. As human with creativity and variant nature, each developer has his or her own way of doing development that may not be allowed by the process model. As a result, various inconsistencies arise in software processes and then the authority of the process model will be undermined. In this paper, we propose an algebraic approach to promote the efficient management of inconsistencies. With the approach, potential inconsistencies can be precisely detected and valuable diagnostic information is available to help process designers efficiently locate the detected inconsistencies. The effectiveness of the approach is demonstrated by experimenting it on an example process.

Designing and Modeling of Covert Channels in Operating Systems

Covert channels are widely considered as a major risk of information leakage in various operating systems, such as desktop, cloud, and mobile systems. The existing works of modeling covert channels have mainly focused on using finite state machines (FSMs) and their transforms to describe the process of covert channel transmission. However, a FSM is rather an abstract model, where information about the shared resource, synchronization, and encoding/decoding cannot be presented in the model, making it difficult for researchers to realize and analyze the covert channels. In this paper, we use the high-level Petri Nets (HLPN) to model the structural and behavioral properties of covert channels. We use the HLPN to model the classic covert channel protocol. Moreover, the results from the analysis of the HLPN model are used to highlight the major shortcomings and interferences in the protocol. Furthermore, we propose two new covert channel models, namely: (a) two channel transmission protocol (TCTP) model and (b) self-adaptive protocol (SAP) model. The TCTP model circumvents the mutual inferences in encoding and synchronization operations; whereas the SAP model uses sleeping time and redundancy check to ensure correct transmission in an environment with strong noise. To demonstrate the correctness and usability of our proposed models in heterogeneous environments, we implement the TCTP and SAP in three different systems: (a) Linux, (b) Xen, and (c) Fiasco.OC. Our implementation also indicates the practicability of the models in heterogeneous, scalable and flexible environments.

Evaluation of the capability of personal software process based on data envelopment analysis

Personal Software Process (PSP) is a defined and measured software process designed to be used by an individual software engineer. For PSP users, it’s important to evaluate the impact of the PSP upon their own personal capabilities of software development. However, the evaluation of capability of PSP is a Variable Return to Scale (VRS) and multivariate input and output problem, which makes traditional evaluation methods useless. In this paper, an evaluation framework for the capability of PSP based on Data Envelopment Analysis (DEA) is proposed. This framework has the advantage of dealing with VRS issues with multivariate input and output. In addition, the input or output variables of the framework can have different measurement units. Therefore, a quantitative and comprehensive result can be returned by this relative efficiency evaluation method and it can support the continuous improvement of PSP.

A vertex centric parallel algorithm for linear temporal logic model checking in Pregel

Linear Temporal Logic (LTL) Model Checking is a very important and popular technique for the automatic verification of safety-critical hardware and software systems, aiming at ensuring their quality. However, it is well known that LTL model checking suffers from the state explosion problem, often leading to insurmountable scalability problems when applying it to real-world systems. While there has been work on distributed algorithms for explicit on-the-fly LTL model checking, these are not sufficiently scalable and capable of tolerating faults during computation, significantly limiting their usefulness in huge cluster environments. Moreover, implementing these algorithms is generally viewed as a very challenging, error-prone task. In this paper, we instead rely on Pregel, a simple yet powerful model for distributed computation on large graphs. Pregel has from the start been designed for efficient, scalable and fault tolerant operation on clusters of thousands of computers, including large cloud setups. To harness Pregels power, we propose a new vertex centric distributed algorithm for explicit LTL model checking of concurrent systems. Experimental results illustrate feasibility and scalability of the proposed algorithm. Compared with other distributed algorithms, our algorithm is more scalable, reliable and efficient. We propose a new vertex centric distributed algorithm for LTL model checking.Algorithm is designed for BSP model and can be implemented in Pregel.The whole model checking procedure can be highly paralleled by BFS.Our algorithm is more scalable, reliable, efficient and expressive.Our proposed algorithm opens the door to reliable model checking implementations.

Creating Process-Agents incrementally by mining process asset library

Software process trustworthiness is the degree of confidence that a software process produces expected trustworthy work products that satisfy requirements. Software processes are dynamic and highly people-dependent. The performance of software processes relies not only on the process itself, but also on the personnels capabilities. Therefore, management of human resources and evaluation of a companys work force capabilities are crucial and will affect software process trustworthiness. Our software process modeling method OEC-SPM (Organization-Entity Capability based Software Process Modeling) has been shown to take into account personnels capabilities and groups software developers with certain capabilities into a Process-Agent, which is a way of organizing human resources and process asset libraries in software organizations, and will help to improve trustworthiness of software processes. This paper proposes a novel method for incrementally mining Process-Agents from process asset libraries to support OEC-SPM. The method can automatically and incrementally create Process-Agents under three scenarios with high efficiency. Furthermore, we assess the method with the data from real industry setting. The results show that the utilization of human resources in an organization can be optimized when personnels capabilities are taken into account. Additionally, reasonable resource scheduling making use of Process-Agents will result in higher trustworthiness.

On mobility of software processes

In this paper, the mobility of software processes is proposed as a novel concept. It is defined as the structural change in a software process resulting from interactions among linked process elements. The concept addresses the essential change in a software process which brings a high variability and unpredictability to process performance. Three categories of the mobility that lead to the structural change are identified and expounded upon. A reference model for describing the concept is put forward based on the polyadic π-calculus. With the mobility of software processes, it is possible to design a new PCSEE and associated PML with increased flexibilities.

Stochastic Process Algebra Based Software Process Simulation Modeling

In recent years, simulation techniques that have been widely used in many other disciplines are being increasingly used in analyzing software processes. However, researchers from software process simulation community tend to build a separate new model with various technologies from traditional software models. This is partially because that software process simulation might take a completely different approach to describe a process under certain circumstances, for instance, a process being modeled as an overall system. Another reason is that traditional software process modeling methods can not provide simulation functions. The gap between traditional software process modeling and software process simulation modeling confined a wider application of simulation approach in the software engineering community. In this paper, we show the possibility of a simulation model being automatically derived from a traditional descriptive process model and thus one does not necessarily need to build a separate simulation model. By doing so, all information in the descriptive models can be reused.

A secure and rapid response architecture for virtual machine migration from an untrusted hypervisor to a trusted one

Two key issues exist during virtual machine (VM) migration in cloud computing. One is when to start migration, and the other is how to determine a reliable target, both of which totally depend on whether the source hypervisor is trusted or not in previous studies. However, once the source hypervisor is not trusted any more, migration will be facing unprecedented challenges. To address the problems, we propose a secure architecture SMIG (secure migration), which defines a new concept of Region Critical TCB and leverages an innovative adjacent integrity measurement (AIM) mechanism. AIM dynamically monitors the integrity of its adjacent hypervisor, and passes the results to the Region Critical TCB, which then determines whether to start migration and where to migrate according to a table named integrity validation table. We have implemented a prototype of SMIG based on the Xen hypervisor. Experimental evaluation result shows that SMIG could detect amalicious hypervisor and start migration to a trusted one rapidly, only incurring a moderate overhead for computing intensive and I/O intensive tasks, and small for others.