  Is software obsolescence a significant risk? To explore this issue, we
analysed a corpus of over 2.5 billion resources corresponding to the UK Web
domain, as crawled between 1996 and 2010. Using the DROID and Apache Tika
identification tools, we examined each resource and captured the results as
extended MIME types, embedding version, software and hardware identifiers
alongside the format information. The combined results form a detailed temporal
format profile of the corpus, which we have made available as open data. We
present the results of our initial analysis of this dataset. We look at image,
HTML and PDF resources in some detail, showing how the usage of different
formats, versions and software implementations has changed over time.
Furthermore, we show that software obsolescence is rare on the web and uncover
evidence indicating that network effects act to stabilise formats against
obsolescence.
