In my post on NuGram and CouchDB, I neglected to mention how the dynamic grammar was authored and, most importantly, tested. Having a repeatable process for testing grammars is very important when developing a speech application, as most grammars change and get more complex over time.

Of course, the grammar was authored with NuGram IDE. NuGram IDE has some great features to test grammars, and especially dynamic grammars. Dynamic grammars (like the streets grammar) have always been more difficult to debug than static grammars. They can be very easy to write for small applications or prototypes (or blog posts…), but in real applications their coverage tests are often (and should!) run in batch as part of an automated build process. But this is often too cumbersome in practice. For instance, a dynamic grammar implemented as a JSP page requires a web application server to run and if the JSP page makes queries to a database, the DB must be running somewhere too. This greatly complicates the setup to make batch coverage tests. Moreover, writing and testing the dynamic grammar requires some programming skills that speech scientists don’t always have (at least not in large organizations).

With NuGram’s template language, a dynamic grammar can be tested in NuGram IDE Basic Edition in two different ways:

• Using predefined data encoded as a JSON object (a JSON context), or
• Using some custom Java code (a Java context).

Both ways require the creation of an instantiation context. It’s simply a mapping between variable names and values. An instantiation context must provide a value for each and every variable used in the grammar template. The values are used to populate the template and produce the resulting (ABNF or XML) grammar. The way the instantiation context is created depends on the type of context. For a JSON context, the instantiation context is the JSON document itself. For the Java context, some Java code populates a map from strings to objects.

The following video shows how to create a JSON context for the street grammar:

This one shows the steps required to create and use a Java context:

Note: there was a subtle (uncovered) bug in the previous version of NuGram IDE. If you want to create Java contexts like in the video above, please make sure to download the latest version.

The whole project used in the videos is available on github. The Java context initializers use the following open-source libraries:

• Ektorp 1.0.2, the CouchDB Java library
• HttpClient  4.0.3
• SLF4J 1.6.1, a simple logging framework

In the next post, I will show how to use the Java context initializer to deploy the streets grammar on the Java-based version of NuGram Server.

And you, how do you test your dynamic grammars?