2 RELATED WORK
First, a standardized metadata schema has become more important
with regard to the reusability of AR content and the
interoperability of AR applications [9]. In the ubiquitous
computing environment, there are a myriad of embedded sensors
and pervasive computers. To provide a context-aware service,
these devices must interact and integrate the information provided
by each of them [10]. In this respect, their heterogeneity causes
problems in terms of the access, transformation, modification,
transmission, and management of computing resources [11].
Therefore, it is necessary to formulate a metadata schema, which
makes data reusable and operable on any system.
Second, several studies have proposed high-level frameworks for
authoring AR content [12,13]. These studies aim to create an
authoring platform that is independent of specific applications or
target hardware setups. However, while the studies considered
user interaction, most did not deal with the integrated contexts of
users and their situations. They confined user interactions to
simple contexts such as user input to trigger a transition of the AR
content. In the ubiquitous media environment, a smart multimedia
service should consider more complex user interactions. Thus, a
sophisticated framework is necessary for a user-centric service.
Third, the 5W1H-based metadata schema has been utilized in
some studies of context-aware services. The efficiency and
usefulness of its structure, composition/decomposition,
interchanges, unification capability, extensibility, and scalability
have been proven for user-centric services [14]. In a service for