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Hypermedia Toolkit
The toolkit approach mentioned by Haan et al., has been attempted by Puttress
and Guimaraes. They have proposed a toolkit that could be used by
application developers to add hypermedia functionality to their existing
toolkit, independent of specific applications or environment.[Puttress & Guimaraes, 1990]
The hypermedia toolkit architecture is similar to other multi-tiered architectures (See Figure 1).
The layers are: Application Software, Hypermedia Toolkit Layer, Storage System, and Representation System.
The hypermedia toolkit consists of the following three components:
- Storage System Interface (also called Eggs): This interface
consists of a set of C++ classes, providing a hypermedia structure to the
stored application data. It provides the mapping between the application above
and the storage system below. Thus, the storage system can be modified or
changed without modifying the application. Similar to the HAM approach, the
data model is made of graphs, contexts, nodes, links, attributes, and symbols.
This interface does not interpret node data - it is just considered as a stream
of bytes with no structure or meaning. It provides version control and
concurrency control mechanisms. There is finer transaction management under
the control of the application.
- Application Interface: This interface is composed of data objects
that communicate with the application above.
- Representation System Interface: This interface is responsible
for the presentation of views using user interface toolkits, independent of the
display platform. The Application Interface and the Representation Interface
are made of a set of C++ classes, together called Hypermedia Object-oriented
Toolkit (HOT). HOT provides the abstractions required for hypermedia
applications while encapsulating the details of the storage and representation
systems. HOT consists of Data classes that include: HGraph, HContext, HNode,
and HLink. It also consists of View classes for each of the Data classes:
HGraphView, HContextView, HNodeView, HLinkView and HFrame.
Figure 1: Hypermedia Toolkit Architecture
[Puttress & Guimaraes, 1990]
Puttress and Guimaraes report that this architecture will be extended to
support multi-user environments, to provide effective means of sharing and
communication between users of hypermedia applications, and exploring means to
the development of collaborative hypermedia.[Puttress & Guimaraes, 1990]
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