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services interfaces (Geller and Turner 2007; Geller and Melton 2008). It
fosters reusability and sharing of models with the goal that altogether
can answer more questions than an individual model. The Model Web,
however, must be understood as a vision—a high-level concept—rather
than a particular architecture or implementation. Indeed, as a vision, it may
be presented through different architectures and implementations.
Nativi et al. (2013) defi nes the Model Web as the “World Wide Web
for models”, and so it makes a lot of sense to build the Model Web upon
similar principles. The authors propose the following four principles upon
which the Model Web vision sits:
Open access: anybody has the freedom to create, share and access
models on the Web.
Minimal barriers to entry: model providers and model users are not
constrained by diffi cult mechanisms to publishing and accessing
models on the Web. The Model Web encourages the use of open
standards to describe and publish models that are publicly accessible
on the Web.
Service-driven approach: Model access is driven by the notion of
services, i.e., in the form of web services.
Scalability: The network of models can grow without being impeded
by implementation and design factors.
Simply put, the Model Web vision would embrace models exposed
as web services and integrated models as the result of composing these
web services by adhering to the SOA principles (Papazoglou et al. 2007;
Papazoglou and van den Heuvel 2007; Friis-Christiensen et al. 2009), i.e.,
the result of one web service (model) can be reused by the next service
(model).
Some examples can help us to materialize the vision of the Model Web
in practical terms. Dubois et al. (2013) presented
eHabitat
, a WPS-based
service for ecological modeling for computing the likelihood of fi nding
ecosystems with equal properties to those specifi ed in a user request. When
used in conjunction with other web services such as those providing data
on species occurrences, bird distribution maps and data on climate changes,
the eHabitat WPS service becomes a key tool for ecological forecasting and
IM in general (Skøien et al. 2013). This is an example of a compound web
service that gives proxy to other backend web services through a common
service interface (WPS) and reuses the results of these services. That's an
example of the principle of service-driven approach.
Feng et al. (2011) and Castronova et al. (2013) also worked on the idea
of sharing models as web services being compliant with the WPS service
interface. Both, however, go one step further by developing approaches to
bring these models as web services into workfl ows that represent complex
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