Quite often I hear people coming up with rather strange explanations why we use graphs, or to be more specific for the Web case, RDF. Some think that the reason is to make the developer’s life harder. Right. It’s so much easier to understand a key-value structure. And there are the ones who claim that we use graphs because the W3C says so (RDF is a W3C standard). Some others say graphs are used because they are the most generic, powerful data structure and you can represent any other simpler data structure, such as a tree (think XML) with it.
The real reason why graphs are in use is much simpler: when you have data sources and you start connecting data items across them, you end up with a graph. You can like it or not, but it’s inevitable.
Now, graphs have a number of desirable properties, including ‘no JOIN costs‘, they are flexible (you can add/remove stuff anywhere) and, for some of the graph formats, including RDF and TopicMaps there exist standardised query languages (SPARQL, TMQL). The latter one is something that many other sorts of NoSQL datastores are lacking and we see people re-inventing the wheel over and over and over again as there is a natural desire to declaratively state a query and leave the details of the execution to a machine.
The community around GraphDBs is growing and next time you have a BigData problem at hand, give it a moment to contemplate if, maybe, your data is of graph shape and consider joining us in the cool kids club.