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This model allows developersto acquire infrastructure resourceswithout knowl-
edge of the internal implementation details of the underlying providers. This pro-
vides an abstract view of infrastructure resources and insulates the application
from API changes arises from the underlying providers. Applications can be de-
ployed and scaled accordingto system constraints, within a given budget, and have
portability across multiple providers. This paper proposes the use of ontologies to
formulate application requirements. These requirements are subsequently used in
the resource mapping process of the proposed model.
3 A Multi-layer Ontological Model
An
ontology
is a formal description of the entities and the relationships be-
tween them within a particular knowledge domain. Ontologies have been used
to describe cloud resources elsewhere. Most cloud-related ontologies are resource-
centric and give definitions from the perspective of the capabilities of a particular
resource provider.
Bernstein et al [2] proposes an ontology-based catalog which describes the
resource capabilities offered by cloud providers, such as CPU, storage and com-
pliance capabilities. Reservoir [4] proposes a service specification mechanism
which includes VM details, application and deployment setings. Mosaic [8] in-
troduces an ontology to describe cloud resources with a set of functional and
non-functional properties. LoM2HiS [3] proposes a framework for mapping low-
level resource metrics to high-level SLA parameters which focuses on hardware
or network attributes. This paper proposes an application-centric multi-layer
ontology that focuses on user requirements rather than just the cloud resources.
In this paper, a three-layer model is used to describe the process of map-
ping application requirements onto cloud resources (see Figure 2). The top layer
uses a
domain-specific ontology
to express high-level application requirements se-
mantically using application specific terminology. Two examples of such domain-
specific requirements are: (i) application data must be processed within UK in
order to be compliant with the UK Data Protection Act; (ii) media file must be
transcoded into
wmv
format and played on
windows phone
device.
Fig. 2.
A multi-layer ontology model