Service-based Software Research Articles

Fog Computing in Optically Networked Space Constellations

This article provides an overview of computing models to describe the frontier in space-based computing, and describes the definitions and ecosystem historically termed Cloud and Edge. It is proposed that optically internetworked, Proliferated Low-Earth Orbit (PLEO) space-based computing should be considered Fog computing, not Cloud nor Edge. Space-based computing should orient toward software paradigms observed in Fog computing such as internetworked, secure, reactive services. Definitions are provided, with comparisons between Cloud, Fog, Edge, and near-term space-based computing. Implications and the ecosystem around space-based computing are discussed. Specifically, improper application of Edge or Cloud computing models to space systems causes misrepresentations and can have real consequences to investments and technology development. To call such systems Edge is to under-represent their capabilities, and suggests a misleading limitation of resources and unreliability of networks. To call such systems Cloud is to over-represent their capabilities, and incorrectly suggest an ease of deployment and operation of commercially-available distributed computing technologies in space. Acceptance of Fog computing as the model for on-orbit processing will advance usage of reactive service-based software instead of less scalable architectures. Unresolved trends and technical risks to fruition of Fog computing in space are also presented.

Graph neural network-based similarity relationship construction model for geospatial services

ABSTRACT During the development of service-based software systems, Geospatial Service (GS) replacement is often performed, which requires the discovery of functionally similar services in service registries to replace failed services. Compared to real-time similarity computations, direct extraction of similar services from constructed similarity relationships can yield higher replacement efficiency. However, missing and inconsistent service-registry information impedes accurate similarity relationship construction. Here, we propose a Graph Neural Network (GNN)-based model for GS Similarity Relationship construction considering service descriptions and tags, which is named GSSR-GNN. As the sparsity of the service similarity relationship graph constructed based on labeled samples limits the information propagation ability, a graph augmentation method for similarity relationship construction among second-order neighbors is proposed. Considering the differences in the semantic-information feature distributions, such as the service descriptions and tags, a feed-forward neural network-based fusion method is designed to embed them into the same vector space. Pre-trained Bidirectional Encoder Representations from Transformers (BERT) and WordNet models are introduced to enhance the service-representation expressiveness. When an enhanced service representation is input to the GNN, the similarity is calculated and the service similarity relationship is obtained. Experimental results show that the proposed model constructs service similarity relationships with high precision, thus improving the service replacement efficiency and reducing the computational cost of service registry during service replacement.

A Knowledge Graph Embedding Based Service Recommendation Method for Service-Based System Development

Web API is an efficient way for Service-based Software (SBS) development, and mashup is a key technology which merges several web services to deal with the increasing complexity of software requirements and expedite the service-based system development. The efficient service recommendation method is vital for the software development. However, the existing methods often suffer from data sparsity or cold start issues, which should lead to bad effects. Currently, this paper starts with SBS development, and proposes a service recommendation method based on knowledge graph embedding and collaborative filtering (CF) technology. In our model, we first construct a refined knowledge graph using SBS-service co-invocation record and SBS and service related information to mine the potential semantics relationship between SBS and service. Then, we learn the SBS and service entities in the knowledge graph. These heterogeneous entities (SBS and service, etc.) are embedded into the low-dimensional space through the representation learning algorithms of Word2vec and TransR, and the distances between SBS and service vectors are calculated. The input of recommendation model is SBS requirement (target SBS), the similarities functional SBS set is extracted from knowledge graph, which can relieve the cold start problem. Meanwhile, the recommendation model uses CF to recommend service to target SBS. Finally, this paper verifies the effectiveness of method on the real-word dataset. Compared with the several state-of-the-art methods, our method has the best service hit rate and ranking quality.

The trace consistency measurement between WFD-net systems

IntroductionHow to measure the trace consistency between process models in workflow net systems have become a crucial part of process mapping, process integration, and difference testing. Workflow net with data (WFD-net) is an effective language to describe a complete model of a workflow net system. Checking their trace consistency is a significant challenge in service-based software engineering. However, most of the existing research on trace consistency measurement has not taken the data into consideration. Therefore, they cannot accurately calculate the trace consistency degree of two WFD-net systems, especially when data operations and guard functions are complex.MethodsWe explore all traces in two WFD-net systems based on guard analysis and data dependencies.ResultsWe point out that the trace consistency degree is uncertain when the values of guard functions are considered.DiscussionWe conduct experiments to evaluate our method and show its effectiveness.

A Process Model for Service-Oriented Development of Embedded Software Systems

The concepts of service-oriented computing (SOC) have previously been used in the embedded systems domain, mostly at the device level in ad hoc manners to achieve advantages of device integration. However, SOC has not been used for the development of embedded software systems (ESS), i.e., software controlling the embedded devices. To fill this gap, a process model is proposed in this article that allows the systematic development of ESS based on SOC concepts. The proposed process consists of analysis and design phases of embedded software development. The analysis phase is concerned with the collection of system information and preparation for system design. Based on this, the service-based software architecture is developed in the design phase. The effectiveness of the proposed process model is demonstrated through its application in the Smart Home case study.

Edge-Based Runtime Verification for the Internet of Things

Complex distributed systems such as the ones induced by Internet of Things (IoT) deployments, are expected to operate in compliance to their requirements. This can be checked by inspecting events flowing throughout the system, typically originating from end-devices and reflecting arbitrary actions, changes in state or sensing. Such events typically reflect the behavior of the overall IoT system – they may indicate executions which satisfy or violate its requirements. This article presents a service-based software architecture and technical framework supporting runtime verification for widely deployed, volatile IoT systems. At the lowest level, systems we consider are comprised of resource-constrained devices connected over wide area networks generating events. In our approach, monitors are deployed on edge components, receiving events originating from end-devices or other edge nodes. Temporal logic properties expressing desired requirements are then evaluated on each edge monitor in a runtime fashion. The system exhibits decentralization since evaluation occurs locally on edge nodes, and verdicts possibly affecting satisfaction of properties on other edge nodes are propagated accordingly. This reduces dependence on cloud infrastructures for IoT data collection and centralized processing. We illustrate how specification and runtime verification can be achieved in practice on a characteristic case study of smart parking. Finally, we demonstrate the feasibility of our design over a testbed instantiation, whereupon we evaluate performance and capacity limits of different hardware classes under monitoring workloads of varying intensity using state-of-the-art LPWAN technology.

A service-based software architecture for enabling the electronic health record storage using Blockchain

The healthcare sector requires computational solutions with reliable authenticity features for the storage and retrieval of electronic health record data. To address this important issue, this article proposes a service-based software architecture to extract data from different legacy databases, standardise the patient's clinical data requirements and store data using different Blockchain technologies. To achieve this, a software architecture has been designed to guarantee the independence of data storage technology. In addition, a data meta-schema and a set of mapping rules have been specified to store and organise clinical data following an international health standard. To validate the solution presented, the real world scenario of a Brazilian healthcare institution has been used to evaluate the data extraction, standardisation and storage capabilities in two Blockchain platforms widely used in the information technology market.

A service-based software architecture for enabling the electronic health record storage using Blockchain

The healthcare sector requires computational solutions with reliable authenticity features for the storage and retrieval of electronic health record data. To address this important issue, this article proposes a service-based software architecture to extract data from different legacy databases, standardise the patient's clinical data requirements and store data using different Blockchain technologies. To achieve this, a software architecture has been designed to guarantee the independence of data storage technology. In addition, a data meta-schema and a set of mapping rules have been specified to store and organise clinical data following an international health standard. To validate the solution presented, the real world scenario of a Brazilian healthcare institution has been used to evaluate the data extraction, standardisation and storage capabilities in two Blockchain platforms widely used in the information technology market.

Reliability assessment of service-based software under operational profile uncertainty

We address the problem of operational reliability assessment through testing of software services delivered on-demand such as Web Services. Software reliability assessment is typically done for a specific operational profile: the profile is needed in testing to select or generate test cases (operational testing) in a way statistically similar to the anticipated use of software in operation; the observations of success/failure of test executions are used to predict software reliability in actual operation. It is well known that unless the profile is accurate, software reliability predictions obtained via operational testing cannot be trusted.We present a new way of dealing with the uncertainty in the operational profile adopting a two-stage Bayesian inference for reliability assessment. The technique relies on the availability of information about partitions of the input space. The approach is demonstrated on contrived examples and on a case study of real Web Services. We discuss the usefulness of the approach in dealing with two important practical problems: i) the true profile in operation differs from the one used in testing, ii) the profile in operation is changing continuously.

Diversified keyword search based web service composition

To assist system engineers in efficiently building service-based software systems, the keyword search based service composition approach on service connection graphs (scgraphs) has been proposed recently. However, due to the ambiguity of keywords, a keyword query may represent a bunch of different user requirements. Thus the current approach that only returns the composition with the optimal Quality of Service (QoS) cannot guarantee to hit the spot. In this paper, in order to satisfy the various possible requirements underlying a given keyword query, we formally introduce the top-k diverse service composition problem, and present a novel diversified keyword search approach on scgraphs to address it. Specifically, we firstly propose an All-Then-Diversify (ATD) algorithm that enumerates all potential compositions by searching a scgraph and then derives the top-k diverse subsets by deriving the maximal independent sets of a similarity graph. Then, due to the possibly large number of potential compositions, we present a Pop-And-Diversify (PAD) algorithm that only maintains a similarity graph of the top compositions that have been found so far during the search and computes its maximal independent sets incrementally until convergence, thereby reducing unnecessary computation overheads. Moreover, we propose two composition similarity measurements w.r.t. the categories or descriptions of services respectively. Lastly, the experimental results on ProgrammableWeb.com demonstrate that, our approach outperforms another state-of-the-art composition diversification approach on both metrics of density and redundancy, and meanwhile, improves the efficiency of diversification significantly.

A PROCESS MODEL FOR THE FORMALISATION OF QUALITY ATTRIBUTES OF SERVICE-BASED SOFTWARE SYSTEMS

The benefits offered by software architectures include providing an improved understanding of high-level relationships amongst systems components and facilitating in making principled decisions between alternatives. A vast majority of architectural decisions are focused on realising functional requirements and often ignore the nonfunctional requirements (quality attributes) altogether or include them as an afterthought. This has a negative impact on the overall acceptance of the software system by its intended users. Moreover, these architectures are specified using diagrammatic notations such as boxes and lines as connectors between them. As a result, such semiformal representations lack precision in their definitions and may lead to misinterpretations of the architecture resulting in errors being introduced at later stages of development. Although several Architectural Description Languages (ADLs) exist for the formalisation of systems architectures, few are designed for formalising nonfunctional requirements. Since ADLs concentrate on component-level representations and not on the system as a whole, their support of non-functional requirements is limited. Additionally, as each ADL normally supports one quality attribute, multiple ADLs are required to cater for various quality attributes. This articles aims to address the challenges of inadequacies of specifying quality attributes in software systems in a manner that is both formal and applicable to a wider range of quality attributes. To achieve this goal, this paper present a process model that assists in formalising the non-functional requirements of a service-based software system and eliminates the need for multiple ADLs. It demonstrates the practicability of the proposed model by applying it to one quality attribute, namely “availability”, using the general purpose Z specification language.

Guest Editor's Introduction: Special Section on Services and Software Engineering Towards Internetware

The six papers in this special section focuses on services and software computing. Services computing provides a foundation to build software systems and applications over the Internet as well as emerging hybrid networked platforms motivated by it. Due to the open, dynamic, and evolving nature of the Internet, new features were born with these Internet-scale and service-based software systems. Such systems should be situation- aware, adaptable, and able to evolve to effectively deal with rapid changes of user requirements and runtime contexts. These emerging software systems enable and require novel methods in conducting software requirement, design, deployment, operation, and maintenance beyond existing services computing technologies. New programming and lifecycle paradigms accommodating such Internet- scale and service-based software systems, referred to as Internetware, are inevitable. The goal of this special section is to present the innovative solutions and challenging technical issues, so as to explore various potential pathways towards Internet-scale and service-based software systems.

Distributed Software Architecture for AGVs for Separation of Dynamic and Static Obstacles

The current trend towards mass customization confronts established mass production systems with specific challenges. In future production layouts will have to provide a high degree of flexibility and changeability in order to be able to respond to the demand for individualized mass products. This leads to a production network in which the work schedule of each product and thus the sequence of the individual production resources are flexibly arranged. A challenge in this scenario is the implementation of material transport between the machines. The use of mobile transport robots to realize a flexible connection of all material sources and sinks proves to be effective. However, the current design forms, as a monolithic AGV system or the use of flexible autonomous units, show specific weaknesses. The paper describes the research approach to establish an intralogistics service-based software architecture as an intralogistics execution system, which contains the elementary functions of a cross-platform use of mobile autonomous systems. One key application is to digitize the workspace of the mobile systems with a distributed system of infrastructural sensors. An embedded unit separates the scenario into static and dynamic obstacles. The method discussed also includes the aggregation of the images with static obstacles to a world model as a basis for global cross-platform routing. Thus, it is possible to include the static obstacles in an early phase of path planning. The researched architecture integrates a routing service, which offers a cross-platform map for each type of transport robots in use. The dynamic obstacles of the respective scenery are tracked directly by the embedded decentralized ceiling sensors. By combining the Hungarian method with a Kalman filter, the trajectory of the detected dynamic obstacles can be determined. Within the discussed method, this information is transmitted directly from the sensor units to the autonomous systems and allows the local path planner to avoid collisions. Within the implementation of both methods in an industrial demonstrator, the functionality of both services could be validated. The necessary real-time capability for a valid collision avoidance was not achieved due to the computing capacities in use.

Locating Faults in MANET-Hosted Software Systems

We present a method to locate faults in service-based software systems hosted on mobile ad hoc networks (MANETs). In such systems, computations are structured as interdependent services distributed across the network, collaborating to satisfy client requests. Faults, which may occur at either or both the service and network layers, propagate by cascading through some subset of the services, from their root causes back to the clients that initiate requests. Fault localization in this environment is especially challenging because the systems are typically subject to a wider variety and higher incidence of faults than those deployed in fixed networks, the resources available to collect and store analysis data are severely limited, and many of the sources of faults are by their nature transient. Our method makes use of service-dependence and fault data that are harvested in the network through decentralized, run-time observations of service interactions and fault symptoms. We have designed timingand Bayesian-based reasoning techniques to analyze the data in the context of a specific fault propagation model. The analysis provides a ranked list of candidate fault locations. Through extensive simulations, we evaluate the performance of our method in terms of its accuracy in correctly ranking root causes under a wide range of operational conditions.

The implementation of digital technologies for operations management: a case study for manufacturing apps

Manufacturing applications address business to business (B2B) with highly customised applications developed for specific requirements, offering highly specialised solution-oriented and service-based software components, systems, and digital tools that aim at a fast and accurate decision-making support system. The purpose of this paper is to describe the implementation of digital technologies for operations management using manufacturing or engineering apps (eApps), for product design and manufacturing processes. In particular, starting from the specific needs of two companies from mature European industries as automotive and food, this work depicts how this kind of solutions can support companies and improve their operations. In particular, related benefits and challenges faced for the full implementation of the developed tools are highlighted. Moreover a business model to exploit the manufacturing apps is also proposed. The business model proposed for the exploitation of the eApps supports the commercialisation of all the revenue streams offered by this rapidly growing sector taking into account the specific needs of the concerned stakeholders through a diversified value proposition.

Reliability Analysis of On-Demand Service-Based Software Systems Considering Failure Dependencies

Service-based software systems (SBSSs) are widely deployed due to the growing trend of distributed computing and cloud computing. It is important to ensure high quality of an SBSS, especially in a strongly competitive market. Existing works on SBSS reliability usually assumed independence of service failures. However, the fact that resource sharing exists in different levels of SBSS operations invalidates this assumption. Ignorance of failure dependencies have been discussed as potentially affecting system reliability predictions and lowering the benefits of design diversity, as typically seen in high-reliability systems. In this paper, we propose a reliability framework that incorporates failure dependence modeling, system reliability modeling, as well as reliability analysis for individual services and for failure sources. The framework is also capable of analyzing the internal structures of popular software fault tolerant (FT) schemes. The proposed method is applied to a travel agency system based upon a real-world practice for verifying its accuracy of reliability modeling and effectiveness of varied reliability measures. The results show that failure dependence of the services is an essential factor for analyzing any valuable SBSS system. Further, a set of reliability measures with different capabilities and complexities are available for assisting SBSS engineers with system improvements.

Fault-tolerant design of local controller for the poloidal field converter control system on ITER

The control system for the Poloidal Field (PF) on ITER is a synchronously networked control system, which has several kinds of computational controllers. The Local Control Cubicles (LCC) play a critical role in the networked control system for they are the interface to all input and output signals. Thus, some additional work must be done to guarantee the LCCs proper operation under influence of faults. This paper mainly analyzes the system demands of the LCCs and faults which have been encountered recently. In order to handle these faults, decoupled service-based software architecture has been proposed. Based on this architecture, fault detection and system recovery methods, such as redundancy and rejuvenation, have been incorporated to achieve a fault-tolerant private network with the aid of QNX operating system. Unlike the conventional method, this method requires no additional hardware and can be achieved relatively easily. To demonstrate effectiveness the LCCs have been successfully tested during the recent PF Converter Unit performance tests for ITER.

Research on Probabilistic Model based Services Composition Compatibility Focusing on Structural Behaviors Modeling

With the increasing of Web services on Internet, services composition requests considering not only the static information compatibility, such as interface grammar and semantic, but also the structural behavior compatibility, i.e., control flow and communication protocol. However, due to the uncertainty of Internet, application failures occurred in service-based software will cause kinds of economic losses. This stochastic phenomenon has been impacted on the structural behavior which makes services composition should take the probabilistic compatibility into account. The probabilistic compatibility needs to compute the degree of compatibility for the effective performance evaluation, which has been an important issue during services collaboration. In this paper, the probabilistic interface automaton is proposed to formalize service behaviors. Then, the synchronized product model is used to the qualitative checking for verifying whether they can interact with each other or not. Third, the probabilistic compatibilities of composite service and component service are discussed for the quantitative computing. Our method provides a reference to generate the correctness and reliable services composition.

An Evolutionary Method for the Formal Specification Construction of Service-Based Software

Service-based software (SBS) modeling is considered as a promising way to develop high-quality service-based systems. One major challenge of this methodology is how to effectively utilize existing software services in the process of system modeling to ensure the reliability of the system while reducing the development cost. In this paper, we propose an evolutionary method for the formal specification construction of SBS to tackle this problem. Initial requirements are gradually transformed into a formal design specification through three steps during which existing services are discovered, filtered, selected and adopted. Candidate services are discovered through a keyword-based searching. Then the services are analyzed from both the structural and behavioral perspectives for filtering. A specification-based testing technique is exploited to rigorously determine which candidate services are finally selected. The selected services are incorporated into the formal design model of the system. We present a case study that was conducted for evaluating the usability of the method. We have also developed a prototype tool for supporting the method to be applied in practice.

Stochastic modelling and simulation approaches to analysing enhanced fault tolerance on service‐based software systems

SummaryPresently, service‐based software systems (SBSSs) have been heavily deployed to fulfil the functionalities of cloud computing and are widely used in many other application fields. Additionally, maintaining functionality and quality of service levels becomes increasingly important for SBSSs; this is because system operational failures may cause great financial loss to an organization. Fault tolerance (FT) is usually used to provide continuous and reliable system service delivery when failures occur. However, the reliability and performance of FT should be carefully analysed because of the overhead of invoking redundant services. It is also noted that the single point of failure on the FT adjudicators as well as the failure correlation also hamper the benefits of FT in SBSSs. To address these problems, this paper proposes two approaches, the stochastic modelling approach and the simulation approach, for analysing the reliability and performance of generalized FT designs. The first approach is suitable for quick analysis at an early design stage, while the second approach is built on top of the ns‐3 simulator and could be well adapted to incorporate varied uncertainty models in the SBSS environments Extensive experiments and analyses uncover some characteristics that could be useful for SBSS engineers. Copyright © 2015 John Wiley & Sons, Ltd.