Information Technology Reference
In-Depth Information
Take these bits in order to know the number of rows. These other bits tell you the number of
columns; then for each pixel, here is a way to get the pixel value
,
then that would make it easier for them to create software to deal with the image.
The same argument applies to the different types of virtualised objects which we
discuss below.
Each of these types of virtualisation will have its own Representation Information
which we may call “virtualisation information”; this Representation Information
will of course need its own Representation Information.
The Wikipedia entry provides an extensive list of types of virtualisation, and
distinguishes between
•
Platform virtualisation, which involves the simulation of virtual machines.
•
Resource virtualisation, which involves the simulation of combined, fragmented,
or simplified resources.
Figure 6.11 indicates in somewhat more detail than Fig.
7.15
a number of layers
in which we expect to use Virtualisation including:
•
Digital Object Storage virtualisation - discussed in
Sect. 16.2.2
.
•
Common information virtualisation
•
Discipline specific information virtualisation
•
Higher level knowledge
•
Access control
•
Processes
Of course even the Persistent Preservation Infrastructure has to be virtualised.
Each of these is discussed in more detail in
Chaps. 16
and
17
, introducing the
various concepts in a logical manner. For simplicity, these discussions do not fol-
low the layering schemes in
Fig. 6.11
or Fig.
7.15
because there are a number of
recursive concepts which can be explained more clearly in this way..
7.8.2 Common Information Virtualisation
The Common Information Virtualisation envisaged in CASPAR tries to extract those
properties of an Information Object which are widely applicable.
7.8.2.1 Simple Objects
There are several types of relatively simple objects which appear again and again
in scientific data, including images, trees, tables and documents. The benefit of this
type of virtualisation is that for each of them one can rely upon a certain - admittedly
simple - behaviours. Despite this simplicity they are powerful and are the basis of
many familiar software applications.
