Our client has an eCommerce site which was developed by an in-house team, and is now showing its age. I work for a firm brought in as external contractors to build a replacement. Part of the current site is a Flash viewer applet which displays media about the product - zoom-able images, 360-degree views, movies, and so on. We need to show the same media the current site does, so we are simply reusing the viewer.

The viewer is embedded on a page in the usual way, and told what media to show by means of an XML file it loads from our server, which is pretty simple for us to generate. We've got this working; it was pretty straightforward.

But what else do we need to do?

The thing is, as far as we're concerned, the viewer is a binary blob which is served from the client's content-distribution network. We embed it, feed it some XML, and it does its job, but we have no power over its internals. It's completely opaque to us - a black box. We can use it to do what it does, but we can't change it, so if we ever need to do something different, we're stuffed.

We're building this site for the client, and when we're done, we'll hand it over for them to maintain. We won't be doing the maintenance ourselves. There's a small team within the client who are working as part of our team, and who will be the ones doing the maintenance. That team only includes one person from the team that built the old site, and it's not someone who knows the image viewer. The people who do know the image viewer are not slated to join our team when our system replaces theirs - they'll be moved to other projects. The documentation on the viewer is extremely thin, and as far as i know doesn't cover the internals at all.

My worry is that if someone doesn't take some positive action, all knowledge of the internal workings of the viewer - even down to where the source code for it is - will be lost. It's possible it already has been.

Is this something to worry about? If so, whose job is it to worry about it? What should they do about it once they've got worried?