Principles of Service Oriented Architectures (SOA) have been successfully applied for the solutions of business problems and related challenges regarding the integration of heterogeneous software systems in business processes. For this purpose, the so-called Big Web Services technology stack with standards like SOAP, WSDL, WS-Addressing or WS-Security was devised and supporting tools were implemented. These standards ensure that there is a level of common understanding between businesses partners and allow for platform independent communication between remote software Services and their composition/coordination with dedicated languages like BPEL or YAWL.

However, due to the perceived complexity of Big Web Services, Restful Web Services that build on well known W3C/IETF standards such as HTTP, XML or URI have been proposed as (lightweight) alternative. In particular, so-called Service Mashups were introduced, which provide solutions to very specific and narrow business integration problems. The ability of non experts to create Mashup applications is considered to increase the productivity of employees in their daily routine work and when working with different companies on joined projects.

In this context, a growing number of Services can be observed that represent real-world business activities which are performed by humans rather than Software. A prominent example is Amazon Mechanical Turk where tasks are distributed to human workers (Turkers) that offer all kind of Services. As a result, additional standards for requesting work of humans via standardized Service interfaces have been devised, including WS-Human Task and Human Provided Services (HPS). These standards allow for the seamless integration of humans into existing workflows and foster the collaboration in so called mixed Service environments of human and software Services.

The parallel rapid development of mobile technologies and their wide spread adoption, led to a situation, where many employees actually do their job while they are moving. Thus, mobile employees often perform Service work remotely at the location of the customer and their work require the availability of mobile handheld devices such as tablets and smartphones. While early mobile Services focused on simple tasks of entering the data in a dedicated handheld device, modern mobile workers often face complex tasks that require the coordination of several activities of different mobile employees.

Consequently, a lightweight approach for Service compositions is also attractive for mobile workers, because existing SOA standards are difficult to implement on mobile devices because of the volatile characteristics of mobile devices in terms of network connectivity and availability due to limitations in terms of power supply. These are the main reasons that past efforts of adopting SOA on mobile devices focused on the consumption of remote (Web) Services from mobile devices, whereas the provision and composition of Services on mobile devices did not receive as much support. Instead, Apps have emerged as primary means for Service provision on mobile devices. Apps are independent pieces of software that offer a well defined set of functionality are controlled by the user. On average, users install approximately between 14 and 40 Apps on their devices that cover a broad range of functionality: social networking, weather, sports, location information, dictionaries, photography and games are among the most common classes of Apps being used.

In our work, we study the applicability of SOA principles with regard to existing (mobile) infrastructures like App Stores and mobile Apps. Specifically, we analyze established SOA principles like Service provision, Service binding, Service discovery and Service composition in the context of mobile devices and investigate the mapping of SOA infrastructure to a mobile infrastructure. We also address the social aspect of mobile Service provision: mobile Services – being bound to a human – run on devices which are controlled by the owner who can decide if a Service is executed (provided) or not.

To address core mobility aspects like limitations of connectivity, we introduce a lightweight programming language called Tweetflows that provides communication mechanisms to invoke Apps remotely and consequently the means to compose Apps. In this regard, we study the application of microblogging services (e.g., Twitter) as communication backbone for the use of mobile Services in a social context.

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