DSL is an overloaded acronym standing for many different things. I first knew it as Digital Subscriber Line for Internet connection, and then Domain Specific Language. Recently I learnt a new one: Damn Small Linux. As you see the word small, you may think it’s for embedded system. It’s not.
I have been reading Martin Fowler’s book Domain-Specific Language during last two months. Now I am not fully done with the book but have a good idea because the rest of the book is about individual DSL patterns, which I think are better read when used.
I got two key points from the book. One is that the key to DSL is semantic model (“The semantics of a program is what it means – that is, what it does when it executes”). You can implement semantic model as APIs/frameworks in system languages like Java. If you are confused by the question, “what is the difference between DSL and normal code on top of high level APIs?
Last summer, Reflex VP engineering Aaron Bawcom visited VMware campus. He is one of the authors of Virtualization For Security: Including Sandboxing, Disaster Recovery, High Availability, Forensic Analysis, And Honeypotting.
During our talk, Aaron told me a secret project called VQL. Because it’s a secret, I didn’t talk about it to anyone. Just before the PEX 2010, we exchanged emails about the VQL. Aaron told me it’s already shipped. So it’s time to broadcast it.
VQL is a DSL that looks like SQL, easy to understand and easy to use. Unlike SQL on data, it’s on virtual resources in vSphere environment. The following is a quick sample. It gets back the VMs installed with SQL servers with verions newer than 9.2 and they are running 10 minutes ago.
SQL Server and VersionMajor >= 9 and VersionMinor >= 2 project vm at 10 minutes ago