34 research outputs found
On the systematic development of domain-specific mashup tools for end users
The recent emergence of mashup tools has refueled research on end user development, i.e., on enabling end-users without programming skills to compose their own applications. Yet, similar to what happened with analogous promises in web service composition and business process management, research has mostly focused on technology and, as a consequence, has failed its objective. In this paper, we propose a domain-specific approach to mashups that is aware of the terminology, concepts, rules, and conventions (the domain) the user is comfortable with. We show what developing a domain-specific mashup tool means, which role the mashup meta-model and the domain model play and how these can be merged into a domain-specific mashup meta-model. We exemplify the approach by implementing a mashup tool for a specific domain (research evaluation) and describe the respective user study. The results of the user study confirm that domain-specific mashup tools indeed lower the entry barrier to mashup development. © 2012 Springer-Verlag
Services approach & overview general tools and resources
The contents of this deliverable are split into three groups. Following an introduction, a concept and vision is sketched on how to establish the necessary natural language processing (NLP) services including the integration of existing resources. Therefore, an overview on the state-of-the-art is given, incorporating technologies developed by the consortium partners and beyond, followed by the service approach and a practical example. Second, a concept and vision on how to create interoperability for the envisioned learning tools to allow for a quick and painless integration into existing learning environment(s) is elaborated. Third, generic paradigms and guidelines for service integration are provided.The work on this publication has been sponsored by the LTfLL STREP that is funded by the European Commission's 7th Framework Programme. Contract 212578 [http://www.ltfll-project.org
EzWeb/FAST: Reporting on a Successful Mashup-based Solution for Developing and Deploying Composite Applications in the Upcoming Web of Services
Service oriented architectures (SOAs) based on Web Services have attracted a great interest and IT investments during the last years, principally in the context of business-to-business integration within corporate intranets. However, they are nowadays evolving to break through enterprise boundaries, in a revolutionary attempt to make the approach pervasive, leading to what we call a user-centric SOA, i.e. a SOA conceived as a Web of Services made up of compositional resources that empowers end-users to ubiquitously exploit these resources by collaboratively remixing them. In this paper we explore the architectural basis, technologies, frameworks and tools considered necessary to face this novel vision of SOA. We also present the rationale behind EzWeb/FAST: an undergoing EU funded project whose first outcomes could serve as a preliminary proof of concep
Optimizing performance of workflow executions under authorization control
“Business processes or workflows are often used to
model enterprise or scientific applications. It has
received considerable attention to automate workflow
executions on computing resources. However, many
workflow scenarios still involve human activities and
consist of a mixture of human tasks and computing
tasks.
Human involvement introduces security and
authorization concerns, requiring restrictions on who
is allowed to perform which tasks at what time. Role-
Based Access Control (RBAC) is a popular authorization
mechanism. In RBAC, the authorization concepts such as
roles and permissions are defined, and various
authorization constraints are supported, including
separation of duty, temporal constraints, etc. Under
RBAC, users are assigned to certain roles, while the
roles are associated with prescribed permissions.
When we assess resource capacities, or evaluate the
performance of workflow executions on supporting
platforms, it is often assumed that when a task is
allocated to a resource, the resource will accept the
task and start the execution once a processor becomes available. However, when the authorization policies
are taken into account,” this assumption may not be
true and the situation becomes more complex. For
example, when a task arrives, a valid and activated
role has to be assigned to a task before the task can
start execution. The deployed authorization
constraints may delay the workflow execution due to
the roles’ availability, or other restrictions on the
role assignments, which will consequently have
negative impact on application performance.
When the authorization constraints are present to
restrict the workflow executions, it entails new
research issues that have not been studied yet in
conventional workflow management. This thesis aims to
investigate these new research issues.
First, it is important to know whether a feasible
authorization solution can be found to enable the
executions of all tasks in a workflow, i.e., check the
feasibility of the deployed authorization constraints.
This thesis studies the issue of the feasibility
checking and models the feasibility checking problem
as a constraints satisfaction problem.
Second, it is useful to know when the performance of
workflow executions will not be affected by the given
authorization constraints. This thesis proposes the
methods to determine the time durations when the given
authorization constraints do not have impact.
Third, when the authorization constraints do have
the performance impact, how can we quantitatively
analyse and determine the impact? When there are multiple choices to assign the roles to the tasks,
will different choices lead to the different
performance impact? If so, can we find an optimal way
to conduct the task-role assignments so that the
performance impact is minimized? This thesis proposes
the method to analyze the delay caused by the
authorization constraints if the workflow arrives
beyond the non-impact time duration calculated above.
Through the analysis of the delay, we realize that the
authorization method, i.e., the method to select the
roles to assign to the tasks affects the length of the
delay caused by the authorization constraints. Based
on this finding, we propose an optimal authorization
method, called the Global Authorization Aware (GAA)
method.
Fourth, a key reason why authorization constraints
may have impact on performance is because the
authorization control directs the tasks to some
particular roles. Then how to determine the level of
workload directed to each role given a set of
authorization constraints? This thesis conducts the
theoretical analysis about how the authorization
constraints direct the workload to the roles, and
proposes the methods to calculate the arriving rate of
the requests directed to each role under the role,
temporal and cardinality constraints.
Finally, the amount of resources allocated to
support each individual role may have impact on the
execution performance of the workflows. Therefore, it
is desired to develop the strategies to determine the
adequate amount of resources when the authorization
control is present in the system. This thesis presents the methods to allocate the appropriate quantity for
resources, including both human resources and
computing resources. Different features of human
resources and computing resources are taken into
account. For human resources, the objective is to
maximize the performance subject to the budgets to
hire the human resources, while for computing
resources, the strategy aims to allocate adequate
amount of computing resources to meet the QoS
requirements
Enhancement of the usability of SOA services for novice users
Recently, the automation of service integration has provided a significant advantage in delivering services to novice users. This art of integrating various services is known as Service Composition and its main purpose is to simplify the development process for web applications and facilitates reuse of services. It is one of the paradigms that enables services to end-users (i.e.service provisioning) through the outsourcing of web contents and it requires users to share and reuse services in more collaborative ways. Most service composers are effective at enabling integration of web contents, but they do not enable universal access across different groups of users. This is because, the currently existing content aggregators require complex interactions in order to create web applications (e.g., Web Service Business Process Execution Language (WS-BPEL)) as a result not all users are able to use such web tools. This trend demands changes in the web tools that end-users use to gain and share information, hence this research uses Mashups as a service composition technique to allow novice users to integrate publicly available Service Oriented Architecture (SOA) services, where there is a minimal active web application development. Mashups being the platforms that integrate disparate web Application Programming Interfaces (APIs) to create user defined web applications; presents a great opportunity for service provisioning. However, their usability for novice users remains invalidated since Mashup tools are not easy to use they require basic programming skills which makes the process of designing and creating Mashups difficult. This is because Mashup tools access heterogeneous web contents using public web APIs and the process of integrating them become complex since web APIs are tailored by different vendors. Moreover, the design of Mashup editors is unnecessary complex; as a result, users do not know where to start when creating Mashups. This research address the gap between Mashup tools and usability by the designing and implementing a semantically enriched Mashup tool to discover, annotate and compose APIs to improve the utilization of SOA services by novice users. The researchers conducted an analysis of the already existing Mashup tools to identify challenges and weaknesses experienced by novice Mashup users. The findings from the requirement analysis formulated the system usability requirements that informed the design and implementation of the proposed Mashup tool. The proposed architecture addressed three layers: composition, annotation and discovery. The researchers developed a simple Mashup tool referred to as soa-Services Provisioner (SerPro) that allowed novice users to create web application flexibly. Its usability and effectiveness was validated. The proposed Mashup tool enhanced the usability of SOA services, since data analysis and results showed that it was usable to novice users by scoring a System Usability Scale (SUS) score of 72.08. Furthermore, this research discusses the research limitations and future work for further improvements
Towards automated composition of convergent services: A survey
A convergent service is defined as a service that exploits the convergence of
communication networks and at the same time takes advantage of features of
the Web. Nowadays, building up a convergent service is not trivial, because
although there are significant approaches that aim to automate the service
composition at different levels in the Web and Telecom domains, selecting
the most appropriate approach for specific case studies is complex due to
the big amount of involved information and the lack of technical considerations.
Thus, in this paper, we identify the relevant phases for convergent
service composition and explore the existing approaches and their associated
technologies for automating each phase. For each technology, the maturity
and results are analysed, as well as the elements that must be considered
prior to their application in real scenarios. Furthermore, we provide research
directions related to the convergent service composition phases