The Design Principles and Practices of Interoperable Smart Spaces - Advanced Design Approaches to Emerging Software Systems - page 35

Table 2. The architectural style of IOP

IOP principle Definition

Shared information The IOP manages a shared information search domain called Smart Space (SS ), accessible and understood by all

the authorized applications. Information is about the objects existing in the environment or about the environment
itself. The information is represented in a uniform and use-case independent way. Information interoperability
and semantics are based on common ontologies that model information.

Simplicity The IOP deals with information. The IOP information level is use-case agnostic.

Service An SS is a service, offered by a service platform and intended for the sharing of interoperable SS information.

Each application may interface to one or more SSs through a Smart Space Application Protocol. Use case specific
functions may be performed at the service level before joining the SS.

Agnostics The IOP is agnostic with respect to the adopted ontology, application programming language, service platform

exposing the SS, communication layer and hosting device/system.

Extensibility The IOP does not provide a-priori defined functionalities to manipulate information, in addition to inserting

and removing the information for sharing. IOP functionality may be extended with domain ontologies and with
information manipulation services. If these services become commonly usable, they are called “IOP extensions”.

Evolvability The IOP should support the addition of new applications. This principle envisages that the IOP provides the

means to implement software that adapts to changes in SS without changing code. For example, if relevant sen-
sor information is added to the SS, the SSA should benefit from it without changing any part of the application.

Context Context management is an IOP extension, according to the extensibility principle. IOP should enable the aggrega-

tion of interoperable information into a higher level of context information, for the benefit of application usability
and IOP performance. As the information returned by the IOP depends on the query and available information,
the ontology is to define context semantics. Context may be managed and used both at the information level and
service level.

Notification Applications may subscribe to be alerted upon a context-change.

Usability User interaction management may become an IOP extension, according to the extensibility principle. The user

interaction model and the usability of SSAs should benefit from the context-dependence principle. The ontology
defines the semantics of interaction events. The interaction between the users, their environment and SSA may
be managed both at the information and service level,

Security and trust Security, privacy and trust management is an IOP extension, handled both at the service level and information

level. Appropriate ontologies define whether the IOP is required to respect privacy, enforce authentication and
access control policies at finer granularity than SS itself, or if the shared information integrity, confidentiality
and trust need to be provided.

Business model The development tools and engineering phases of SSAs should be consistent with the IOP business models and

mapped to the value chain(s) of the smart space stakeholders.

Legacy Legacy devices and systems access and exchange information with the SS through a simple use-case independent

protocol. Such exchanged information is modeled by Domain Ontologies. Legacy devices may provide informa-
tion to the SS and subscribe to information from it.

Scalability The IOP should scale with respect to the number of the users, devices, and resources available on each device,

the amount of information stored in the SS, and the number of SSs.

Performance Performance monitoring is an IOP extension. Performance of IOP realizations and SSAs should be evaluated at

the development time and be measurable at run time. The criteria for run time performance monitoring should
be defined through performance metrics ontology.

Reliability Availability The reliability and availability of every IOP instance and of SSAs should be evaluated at development time and

be measurable at run time.

Productivity SSA development tools should support easy and fast agents and the application development with software reuse.

SIB and the KPs, is called Smart Space Access
Protocol (SSAP). IOP can be taken into use either
through standard TCP/IP sockets or by integrat-
ing it with some middleware technologies that

support service oriented architecture. Examples
of these kinds of middleware technologies are
OSGi, NoTA, and Web Services. OSGi combines
component and service oriented architecture appli-