Once built, a site is generally functional, and built according to the initial vision and specification.

All too often though, there are later ideas for improvement or changes which, if an implementation is large, may result in additional costs and developer time.

In this section, we look at the effort needed to add a few features to an already functional site, and explore the impact of these changes on existing code:

• Adding a hierarchical index for all pages, and the ability to navigate through the site using the index.
• A feature allowing the content of the wiki to be exported in book format as a PDF document.
• Re-styling the whole site, using bootstrap to produce a mobile ready reactive interface.
• Adding a comment section to each page by using Disqus as a collaborative tool.

The ease with which a site can be extended speaks volumes about maintainability.  One's ability to maintain a site or extend it without impacting on concurrent development or having to make large changes to existing code determines one's exposure to risk and has a direct cost implication.