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ogy developed by DuraSpace that makes it easy
for organizations and end users to use cloud
services. DuraCloud leverages existing cloud
infrastructure to enable durability and access to
digital content. DuraCloud particularly focuses
on providing preservation support services and
access services for academic libraries, academic
research centers, and other cultural heritage orga-
nizations. The service builds on the pure storage
from expert storage providers by overlaying the
access functionality and preservation support tools
that are essential to ensuring long-term access and
durability. DuraCloud offers cloud storage across
multiple commercial and non-commercial provid-
ers, as well as compute services that are keys to
unlocking the value of digital content stored in the
cloud. DuraCloud provides services that enable
digital preservation, data access, transformation,
and data sharing. Customers are offered “elastic
capacity” coupled with a “pay as you go” ap-
proach. DuraCloud is appropriate for individuals,
single institutions, or for multiple organizations
that want to use cross-institutional infrastructure.
DuraCloud has been in a pilot phase since the
beginning of fall 2009 and will be released as a
service of the DuraSpace not-for-profit organiza-
tion in the fall of 2010.
Through the surveying of the two aforemen-
tioned projects, we are able to compare our work
(A service component model and implementation
for institutional repositories) with theirs. In actu-
ality, the two projects share some commonality
with our work: all try to bring in the advantages
that cloud services provide such as flexibility,
scalability, elasticity and a pay-per-use model that
are inherent in cloud. Nevertheless, these three
works have different emphases.
With regard to Fedorazon, its objectives are
fairly clear. It is a preconfigured instance of Fe-
dora repository installed on rentable servers from
Amazon so as to host the computing stack (EC2)
and the storage components (S3). In this case, In
Fedorazon, cloud means virtual server services
as provided by Amazon. As for DuraCloud, their
idea is more similar to ours than Fedorazon's.
DuraCloud is a mediator between institutional or
end-user applications and a variety of 3rd party
cloud services. The purpose of the service is to
provide a trusted intermediary that offers dif-
ferent levels of service aimed at making digital
content durable and usable (DuraCloud Overview
2009). In this case, in DuraCloud, cloud menas
not only Amazon but also other 3rd party cloud
storage and computing services, yet DuraCloud
still needs to store some information needed to
mediate storage and retrieval of content with 3rd
party storage providers. In comparison, our work
(A service component model and implementation
for institutional repositories) lies on more cloud
services than the envisioned DuraCloud project
(as it begins at fall of 2009 and still in its process)
because the middleware we designed does not
have to locally store the content of one resource,
and it even does not need to store its metadata
and other extra information. By doing so, it will
bring convenience to an institution while they set
up their own repository.
Next, we'll describe the digital resource service
component model we designed in detail, which
targets to support cloud services easily and enhance
the efficiency of managing digital resources.
3. SERVICE COMPONENT MODEL
OF DIGITAL RESOURCES
To manage a digital resources effectively, it is
necessary to define a model to identify the related
information and categorize the functions. Fedora
regards that a digital object is composed of: identi-
fier, object properties, data-streams that represents
MIME-typed content items and disseminators
that associate external services with the object for
the purpose of providing extensible views of the
object or of its data stream content (Lagoze et al.
2006). There are three kinds of digital objects in
Fedora: data objects, Behavior Definition Objects,
and Behavior Mechanism Object (Smith 2002).
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