I work on applications that interface with other applications using Web Services, and XML feeds. These apps help track employee information for different companies to track thing like pay, performance, and security issues. The problem is, I don’t know where the actual content is originating from. That can be problematic, because you are assuming that your data provider will let you know if there is a format change or discontinuation coming down the pipe. Typically, the provider will let you know, somehow. However, in the case of systems “piggy backing” on data of other systems, then in turn, providing that data to further systems, eventually, the message of change gets lost.
I found this out the hard way a couple weeks ago. Luckily for me, it was for a low priority system. I manage a series of blogs for a corporation. I don’t manage the content, but I taker care of the themes and plugins. One of the plugins that I wrote was a “Company Updates” plugin, basically an RSS type of news reader that uses plain XML, and not the RSS standard. The data was coming from what I thought to be the HR department. However, they were just sending it to me through a XML feed, as they were getting it from a small group in the company who were generating the data by hand. Well this group changed the format of the XML tags, and notified HR. But HR didn’t notify me. All of a sudden, I come to work and all of the Blog users were calling me because the “Company Updates” feed was busted. I noticed the change in the XML feed, so I fixed the problem. However I couldn’t understand why I wasn’t notified.
I contacted HR, and they didn’t know anything because they never wrote the Change notification down. Apparently the employee who was notified about the change assumed that in my super natural power over XML feeds, my plugin would have updated dynamically with the XML change. True, if I had a DTD or Schema, I could have written a more intelligent plugin, but I didn’t have a DTD or Schema, and this was a pretty small system. In this case, it is easier to modify the code as changes occur. Anyway, the HR people got me in touch with the group who produces the feed. They told me about the notifications. Needless to say, I switched the origin of the feed to this group.
The moral of the story is that documentation is a REALLY good thing. In this case the problem was small, and easily rectified. However, it made me review my other interfaces, and I decided to write up a Provider/Consumer agreement about data, so the actual origin of the data is known. This agreement is review by all parties in involved and helps to keep me in the loop when changes happen.
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