9.3 Changing the Point of View 195
enforced. Furthermore, if the company chooses to change its style, it can do
so by simply changing the stylesheets that define the style. Neither the con-
tent nor the logical structure needs to be changed, and no employee needs to
be involved.
Summary
- Transformation is an effective means for controlling how data are pre-
sented.
- Information transformation is performed in a series of steps to reduce the
overall effort and to separate concerns.
- Different individuals and groups of individuals are concerned with each
step of the transformation process.
9.3 Changing the Point of View
An XML document is an organized repository of information. Information is
stored in a series of nested elements that act in some ways like the directories
and files of a file system, as discussed in section 1.4. However, hierarchical
structures are inflexible: the organization requires a commitment to a partic-
ular point of view. In this section we discuss what this involves and how to
deal with it using transformations.
Consider microarray information. This information consists of binding po-
tentials (which can be expressed in several ways) of proteins to a collection of
small molecules. One could choose to represent these data from the protein
point of view in which case the XML document would look something this:
...
<Protein id="Mas375">
<Substrate id="Sub89032">
<BindingStrength>5.67</BindingStrength>
<Concentration unit="nm">43</Concentration>
</Substrate>
<Substrate id="Sub8933">
<BindingStrength>4.37</BindingStrength>
<Concentration unit="nm">75</Concentration>
</Substrate>
...
