Earlier quoted context omitted.
Depending on the complexity of your computations and state, what you just described can basically become unusable. For example, an app I work on implements a spec which: - Models state as an arbitrary DAG - With arbitrarily deep dependency chains - Which may trigger dependent nodes based on only subsets of their state - Based on computations of arbitrary XPath expressions, sometimes containing non-native extensions;…
Would love to know what the app does. From the mentions of xpath all I can think is "visual xml editor"?
could be using data returned in XML format because there is no JSON endpoint for that particular data source.
XPath is also nice for dealing with just about any complex markup tree, for example if you needed to extract data from serialized DOMs that were sent to your application somehow.
How about SVG tools using XPath?