Recently a colleague stated that in theory, caching could be considered 'evil'. Now 'evil' is a very broad term which is used a lot in the IT community, but what does it really mean when we're talking about technical solutions? I asked around, but couldn't find a clear cut definition, so I went searching...

In his search he came across a wide range of definitions, including one mentioning bad design or implying a lack of goals with a summarized meaning of "does harm to your aesthetic and engineering judgment". He applies this to caching and, because of it being a sort of counter-intuitive way to handle content (not just the pull and push), it could be considered slightly evil. Interesting interpretation...

However, as anyone will tell you caching is a very necessary evil. [...] So while it does some minor harm to aesthetic and engineering judgment, the user gets a fast experience, which is really all that matters in the end.

These aspects include things like examples of the elements it can contain, elements that are required for it to be a compliant RSS document, a look at the enhanced RSS functionality and structure (more information about the creator of the RSS embedded in the data), and even a look at what an aggregator is and what they would do with your RSS file.

Keep an eye out for the last installment in the series - a look at actually creating the RSS file from your data (probably from a database) and displaying it for the world to see.