Abstract Business process model and notation (BPMN) is a popular notation used for process modelling mainly due to its high expressiveness. However, BPMN has shortcomings when dealing with specific domains (namely Hazard Analysis and Critical Control Points systems), struggling to model activity duration, quality control points, activity effects and monitoring nature. To tackle these limitations, the business process model and notation extended expressiveness (BPMN-E2) was proposed. In this paper, a multiperspective conformance checking algorithm is developed focusing on detecting non-conformity between an event log and a process model, regarding the information provided by the new elements within BPMN-E2. The proposed algorithm follows a two-step approach that starts by converting the model into a directly follows model (annotated with conformance rules), which is then used in a second phase to perform conformance checking effectively. This modular approach allows to apply the proposed algorithm to other process model notations than BPMN-E2. An event log clustering technique was also developed to downsize large-event logs without compromising data relevance. In this way, both the multiperspective algorithm and the log-downsize clustering technique here proposed are a key contribution to improve conformance checking in process modelling, as evinced in the proof-of-concept provided.

Adaptability and energy-efficient sensing are essential properties to sustain the easy deployment and lifetime of WSNs. These properties assume a stronger role in autonomous sensing environments where the application objectives or the parameters under measurement vary, and human intervention is not viable. In this context, this paper proposes LiteSense, a self-adaptive sampling scheme for WSNs, which aims at capturing accurately the behavior of the physical parameters of interest in each WSN context yet reducing the overhead in terms of sensing events and, consequently, the energy consumption. For this purpose, a set of low-complexity rules auto-regulates the sensing frequency depending on the observed parameter variation. Resorting to real environmental datasets, we provide statistical results showing the ability of LiteSense in reducing sensing activity and power consumption, while keeping the estimation accuracy of sensing events.

Understanding network workload through the characterization of network flows, being essential for assisting network management tasks, can benefit largely from traffic sampling as long as an accurate snapshot of network behavior is captured. This paper is devoted to evaluate the real applicability of using sampling to support flow analysis. Considering both classical and emerging sampling techniques, a comparative performance study is carried out to assess the accuracy of estimating flow parameters through sampling. After identifying the main building blocks of sampled-based measurements, a sampling framework has been implemented to provide a versatile and fair platform for carrying out the testing and comparison process. Through an encompassing coverage of representative sampling techniques, the present study aims to provide useful insights regarding the use of sampling in traffic flow analysis.

Within network measurement context, traffic sampling has been targeted as a promising solution to cope with the huge amount of traffic traversing network devices as only a subset of packets is elected for analysis. Although this brings an evident advantage to measurement overhead, the computational burden of performing sampling tasks in network equipment may overshadow the potential benefits of sampling. Attending that sampling techniques evince distinct temporal and spatial characteristics in handling traffic, this paper is focused on studying the computational weight of current and emerging techniques in terms of memory consumption, CPU load and data volume. Furthermore, the accuracy of these techniques in estimating network parameters such as throughput is evaluated. A sampling framework has also been implemented in order to provide a versatile and fair platform for carrying out the testing and comparison process.

Traffic Sampling is a crucial step towards scalable network measurements, enclosing manifold challenges. The wide variety of foreseeable sampling scenarios demands for a modular view of sampling components and features, grounded on a consistent architecture. Articulating the measurement scope, the required information model and the adequate sampling strategy is a major design issue for achieving an encompassing and efficient sampling solution. This is the main focus of the present work, where a layered architecture, a taxonomy of existing sampling techniques distinguishing their inner characteristics and a flexible framework able to combine these characteristics are introduced. In addition, a new multiadaptive technique proposal, based on linear prediction, allows to reduce the measurement overhead significantly, while assuring that traffic samples reflect the statistical behavior of the global traffic under analysis.

Facing the huge traffic volumes involved in today's networks it is of utmost importance to deploy efficient network measurement solutions to assist network management and traffic engineering tasks correctly, without interfering with normal network operation. Sampling techniques contribute effectively for this purpose as the amount of traffic processed is reduced, ideally without endangering the accuracy of network statistical behavior estimation. Although recent proposals of sampling techniques tend to improve the correctness of the estimation process, their underlying overhead is yet considerably when handling high traffic volumes. This paper proposes a new traffic sampling technique for performing lightweight network measurements. This technique, based on linear prediction, is multiadaptive regarding the packet sampling process, allowing to reduce significantly the amount of traffic under analysis while maintaining the representativeness of network samples for accurate network parameters' estimation. The performance evaluation of the sampling technique demonstrates the effectiveness and versatility of the proposal when considering real traces representing distinct traffic load scenarios. The statistical analysis provided evinces that the present solution outperforms classic sampling techniques, both in accuracy and amount of data involved in the measurement process.

Handling quality requirements of multimedia services and the expectations of end-users regarding the perceived service quality is currently a major issue for service providers in order to sustain service diversity and improve competitiveness. In this context, this paper presents ongoing work toward a service-oriented architecture for QoE/QoS evaluation and control, which can be deployed to assist the provision of multi- constrained services. Considering the users' QoE perspective and the negotiated service levels, the architecture lays on per service class online monitoring to assist self-adaptive control of multimedia flows entering the network. To perform online monitoring, a distributed and versatile QoS monitoring tool oriented to multiservice networks is proposed. Preliminary results shows that the presented control strategy is effective in providing consistent quality levels to heterogeneous services.

The recent commitment of European Universities to join a global wireless access and roaming infrastructure through the eduroam initiative has brought many advantages to the academic community. In a new environment of increasing user mobility, it is useful to study and understand the users' behaviour when accessing the wireless network infrastructure. This paper is focused on characterising the real network usage within university campuses, based on WLAN traffic traces collected at the University of Minho (Portugal). The obtained results, allowing to identify user trends and quantify the influence of access location on the number of associated users, the number and duration of sessions, the volume of generated traffic, and user mobility indicators, provide important directions for planning future improvements of university WLANs.

To increase the trust and acceptance of Next Generation Networks (NGN) by new and existing subscribers, it is necessary to ensure that the most popular services of legacy networks (GSM/GPRS) are still in place. The Short Message Service (SMS) is a widespread data service with high revenue for telecommunication operators, which allows the exchange of short messages between fixed, mobile and, indirectly, Internet subscribers. In this context, it is essential to extend this service for the NGN and allow its interaction with the new messaging services. With that in mind, a study was carried out to ensure the coexistence between SMS and the Instant Messaging (IM) service present in NGN. The present study identifies the relevant technical specifications impacting on the functionality of the IP Multimedia Subsystem (IMS) messaging services so that the interoperability with SMS can be ensured. The results of this study, covered in this article, aim to help the comprehension of the proposed interoperability solution, and demonstrate that the exchange of messages between legacy and NGN messaging services or equipment can be successfully accomplished. In this context, both SMS and IMS messaging services are detailed, along with the main protocols they involve. Finally, the entity responsible for ensuring message interoperability the IP Short Message Gateway (IP-SM-GW) is presented and tested in a commercial delivery content testbed.

In multiservice networks, admission control (AC) is a convenient means of assuring high quality communications by safeguarding enough availability for customer traffic. This can be particularly useful to preserve the quality of services such as IP telephony and video conferencing, and to ensure acceptable throughput to elastic flows. This paper tackles the problematic of performing implicit AC in multiservice networks, pointing out a flexible yet simple to deploy solution for controlling flows which do not explicitly send signaling admission requests. This allows to complement the explicit AC case, widening the ability to integrate services and applications in a transparent way. The versatility and self-adaptability of the proposed distributed AC criteria in ensuring the quality of multiple services is also proved.

Comunicação apresentada na "Consumer Communications & Networkin Conference 2006", Las Vegas, Nevada, USA, 8-10 Janeiro 2006.

Distributed service-oriented traffic control mechanisms, operating with minimum impact on network performance, assume a crucial role as regards controlling services quality and network resources transparent and efficiently. In this way, we describe and specify a lightweight distributed admission control (AC) model which provides an uniform solution for managing QoS and SLSs in multiclass and multidomain environments. Taking advantage of the consensual need of on-line service monitoring and traffic control at the network edges, AC decisions are driven by feedback from systematic edge-to-edge measurements of relevant QoS parameters for each service type and SLS utilization. This allows self-adaptive service and resource management, while abstracting from network core complexity and heterogeneity. In this paper, introducing an expressive notation, we specify the high-level entities for multiservice provisioning in a domain and formalize service-dependent AC equations to assure both intra and interdomain model operation. A proof-of-concept of the AC criteria effectiveness in satisfying each service class commitments while achieving high network utilization is provided through simulation.

This paper addresses the problem of formalizing service level specifications (SLSs) as a first step to simplify and automate the configuration and management of multiservice IP networks. A formal representation of SLSs will allow their automatic validation and processing, fostering the dynamic negotiation of SLSs and the interoperability among service management entities. In this way, taking advantage of XML extensibility and portability, a Schema is presented describing XML SLSs sections and their contents. In addition, an XML validator tool was built to check if SLSs are correctly specified. An XML SLS for an IP telephony service is used to exemplify this proposal expressiveness.

Achieving an admission control strategy for CoS networks covering both intra-domain and end-to-end operation is still an open issue. This paper discusses how AC can be carried out without adding significant complexity to the network control plane and proposes a distributed service-oriented AC model for these networks. The model only involves the network edge nodes leaving the network core unchanged. Ingress nodes perform implicit or explicit service-dependent AC based on both QoS and SLSs utilization metrics, obtained through edge-to-edge online monitoring performed at egress nodes. From an end-to-end perspective, the flow request is used both for AC and available service computation. Relevant aspects of the model interrelated areas and implementation key points are also discussed.