Frameworks for Distributed Interoperability

Introduction

Interoperability (between two or more systems) is a word formed by the juxtaposition of a prefix (inter) and the agglutination of two other words (operate and ability) and means the ability (of two or more systems) to operate together.

What these two last words really mean depends largely on the domain which the systems belong to, although there is a pervasive, underlying notion that these systems are active, reacting upon stimuli sent by others and cooperating to accomplish higher level goals than those achievable by each single system.

Interoperability has been studied in domains such as enterprise cooperation (Jardim-Goncalves, Agostinho, & Steiger-Garcao, 2012), e-government services (Gottschalk & Solli-Sæther, 2008), military operations (Wyatt, Griendling, & Mavris, 2012), cloud computing (Loutas, Kamateri, Bosi, & Tarabanis, 2011), healthcare applications (Weber-Jahnke, Peyton, & Topaloglou, 2012), digital libraries (El Raheb et al., 2011) and metadata (Haslhofer & Klas, 2010).

In this article, we adopt a more general perspective, exploring interoperability in the context of distributed systems, independently of what they are or which domain is the most relevant to them. Distributed is used here as a synonym of lifecycle independence, not necessarily implying geographical dispersion. In other words, two systems are distributed if one can evolve (to a new version) without having to change, to suspend or to stop the behavior or interface of the other.

The main goals are:

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  To contribute to a better understanding of what distributed interoperability is and what is really involved;

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  To propose an interoperability framework, which can be defined as a set of principles, assumptions, rules and guidelines to analyze, to structure and to classify the concepts and concerns of interoperability;

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  To exploit partial interoperability through the concepts of compliance and conformance.

This article is structured as follows. The next section describes some of the most relevant existing interoperability frameworks. The following section introduces the basic concepts that establish a foundation for interoperability in distributed contexts. Next, a multidimensional interoperability framework is proposed and its advantages discussed. Finally, future research directions are hinted and conclusions drawn.

Background

One of the first systematizations of distributed interoperability was accomplished by the Open Systems Interconnection (OSI) reference model, a standard since 1984 (ISO, 1994), which considers seven layers (Table 1). This standard deals mostly with communication issues, with the objective of sending data and reproducing it at the receiver. How those data are interpreted by the receiver and how it reacts to the data is left unspecified, encompassed by the topmost layer, Application. Since interoperability must ensure not only data exchange but also meaningful use of information (ISO/IEC/IEEE, 2010), we need to detail the Application layer.