Internet of Things (IoT) devices have been widely adopted in recent years. Unlike conventional information systems, IoT solutions have greater access to real-world contextual data and are typically deployed in an environment that cannot be fully controlled, and these circumstances create new challenges and opportunities. In this article, we leverage the knowledge that an IoT device has about its network context to provide an additional security factor. The device periodically scans a network and reports a list of all devices in the network. The server analyzes movements in the network and subsequently reacts to suspicious events. This article describes how our method can detect network changes, retrieved only from scanning devices in the network. To demonstrate the proposed solution, we perform a multiweek case study on a network with hundreds of active devices and confirm that our method can detect network anomalies or changes.

Graphs are very widely used to represent datasets in various real-world applications. Many algorithms dealing with graphs represent them in the form of sparse matrices and process them through sparse matrix operations. Recently, as the size of a graph increases rapidly, a single-machine-based graph engine has emerged as a general framework for effectively performing large-scale sparse matrix operations. Sparse matrices multiplication (SpGEMM) is a core building block for developing a variety of graph algorithms such as all source shortest paths, betweenness centrality, breadth first search from multiple sources, subgraph indexing, and graph construction. This paper addresses how to perform two sparse matrices multiplication (SpGEMM) efficiently on a single-machine-based graph engine. To effectively perform the large-scale SpGEMM, we have two issues: (1) selecting an appropriate type of matrix products (i.e., inner products, outer products, and row-row products), and (2) allocating memory space to matrices according to different types of matrix products. We first formulate the cost models for the three matrix product types by reflecting their characteristics. We observed the commonality in the processes of the matrix multiplication and the join in a relational database. Based on this observation, we propose memory allocation schemes for three matrix products by borrowing the idea of memory allocation employed in join. Finally, we show the effectiveness of our approach via extensive experiments with real-life datasets.

Special issue on software

In this paper, we present an approach to verify whether a UML design model satisfies its domain-specific security and time-related requirements in an integrated tool environment. This approach is based on a UML metamodel extension mechanism given as profiles. As a model verification tool, we chose the USE (UML-based Specification Environment) since additional functional and non-functional constraints in a UML model should be formally specified using the OCL (Object Constraint Language). In order to address both security and timing properties together in a model, we combine two profiles, UMLsec for security and MARTE (UML profile for Modeling and Analysis of Real-Time and Embedded systems) for time, into the UML metamodel. Then, this combined metamodel is converted to a form of USE specification so that it can be used for verifying models using USE. In this approach, however, this combined metamodel is considered as a large class model in USE because USE does not support profiles. Therefore, models to be verified are created as object models that are instances of the given class model, i.e. the extended metamodel in our case. Our approach is illustrated with a distributed, interoperable wireless communications-based railroad control system called the Positive Train Control (PTC) System.

Access control features are often spread across and tangled with other functionality in a design. This makes modifying and replacing these features in a design difficult. Aspect-oriented modeling (AOM) techniques can be used to support separation of access control concerns from other application design concerns. Using an AOM approach, access control features are described by aspect models and other application features are described by a primary model. Composition of aspect and primary models yields a design model in which access control features are integrated with other application features. In this paper, we present, through an example, an AOM approach that supports verifiable composition of behaviors described in access control aspect models and primary models. Given an aspect model, a primary model, and a specified property, the composition technique produces proof obligations as the behavioral descriptions in the aspect and primary models are composed. One has to discharge the proof obligations to establish that the composed model has the specified property.

Informally described design patterns are useful for communicating proven solutions for recurring design problems to developers, but they cannot be used as compliance points against which solutions that claim to conform to the patterns are checked. Pattern specification languages that utilize mathematical notation provide the needed formality, but often at the expense of usability. We present a rigorous and practical technique for specifying pattern solutions expressed in the unified modeling language (UML). The specification technique paves the way for the development of tools that support rigorous application of design patterns to UML design models. The technique has been used to create specifications of solutions for several popular design patterns. We illustrate the use of the technique by specifying observer and visitor pattern solutions.

Design patterns describe solutions to recurring design problems in the development of software designs. To encourage the use of design patterns, we are investigating tool support for incorporating patterns into UML models. The development of such tools requires patterns to be specified at the metamodel level. Patterns may be specified using roles, where a role is played by model elements. However, the notion of role in the object-oriented community is strictly based on objects, and does not allow the use of the word "role" in any other place where the context is not object-based. In this paper, we propose a notion of role that can be used to specify design patterns at the metamodel level. We survey the characteristics of object-based roles and generalize them. Based on the generalized notion of a role define a new notion of a model role which is played by a model element. We illustrate the use of model roles with a specification of a variant of the Observer design pattern.

Cost-effective development of large, integrated computer-based systems can be realized through systematic reuse of development experiences throughout the development process. We describe a technique for representing reusable modeling experiences. The technique allows developers to express domain-specific design patterns as a sub-language of the modeling language, the UML. Use of the sub-language to build application-specific UML models results in the reuse of the embedded design experiences. We use a notation called the (meta)Role-Based Modeling Language (RBML) to define UML sub-languages. A (meta-)Role Model is a specialization of the UML (Unified Modeling Language) meta-model, that is, it determines a sub-language of the UML. We show how RBML can be used to define domain-specific design patterns.