Abstract
One of the fundamental problems to tackle when interconnecting distributed systems is to entail the minimum coupling possible while ensuring the minimum interoperability requirements. This article presents a solution to the coupling problem based on the concepts of compliance and conformance, in which compatibility between interacting services does not rely on a shared schema, but rather on the features that are actually used. To help systematizing the various aspects relevant to interoperability, this article proposes a multidimensional interoperability framework, which includes the following dimensions: Lifecycle (with typical development stages), Interoperability (based on compliance and conformance, with various layers of abstraction), and Concerns (to deal with non-functional aspects such as security, quality of service and social and legal issues).
TopBackground
The Open Systems Interconnection (OSI) reference model (ISO/IEC, 1994), constitutes one of the first systematizations of distributed interoperability, considering 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. However, interoperability must ensure not only the exchange of data but also the meaningful use of information (ISO/IEC/IEEE, 2010), which means that this layer must be detailed.
Table 1 depicts the basic structure of several interoperability frameworks (referred to by acronym or first author) that use this layered approach, establishing a rough horizontal correspondence between layers.
Table 1. Comparison between several layered interoperability frameworks
OSI
(1994) | C4IF
(2006) | Lewis
(2008) | Stamper
(2000) | LCIM
(2009) | EIF
(2010) | Monfelt
(2011) |
| Application | Collaboration | Organizational | Social world | Conceptual | Political | SWOT |
| Cultural |
| Ethical |
| Legal | Legal |
| Pragmatic | Dynamic | Organizational | Managerial |
| Pragmatic | Organizational |
| Consolidation | Semantic | Semantic | Semantic | Semantic (includes syntactic) | Adaptation |
| Application |
| Presentation | Communication | Syntactic | Syntactic | Syntactic | Presentation |
| Session | Session |
| Transport | Machine | Empirics | Technical | Technical | Transport |
| Network | Connection | Network |
| Link | Link |
| Physical Medium | Physical world | Physical Medium |
Key Terms in this Chapter
Interoperability: The ability of a consumer C to be partially or fully compatible with a provider P . By composition, it can also refer to multilateral compatibility between several systems, interacting in the context of some choreography.
Conformance: Asymmetric property between a provider P and a consumer C ( P conforms to C ) that indicates that P fulfills all the expectations of C in terms of the effects caused by its requests.
Layers of Interoperability: Organization of interoperability concepts and concerns along a single dimension, in layers of monotonically varying degree of complexity and abstraction.
Dimensions of Interoperability: Organization of an interoperability framework that defines several axes, or dimensions, of orthogonal interoperability concerns. This allows a better specification of an interoperability problem than by using just a single dimension of interoperability layers.
Consumer: A role performed by a system A in an interaction with another B , which involves making a request to B and typically waiting for a response.
Interoperability Framework: Set of principles, assumptions, rules and guidelines to analyze, structure and classify the concepts and concerns of interoperability.
Choreography: Contract between two or more systems, which establishes how they cooperate to achieve some common goal.
Compliance: Asymmetric property between a consumer C and a provider P ( C is compliant with P ) that indicates that C satisfies all the requirements of P in terms of accepting requests.
Distributed Interoperability: Interoperability between systems that have independent lifecycles. This means that they can evolve (to a new version) without having to change, to suspend or to stop the behavior or interface of the other. Distribution does not necessarily imply geographical dispersion.