ATL EMF Transformation Virtual Machine (research VM)
Since 2011, the ATL tools include a research VM (EMFTVM), which allows for experimentation with advanced language features. Currently, these features include:
- New bytecode format with explicit representation of rules
- Compiler defined as higher-order ATL transformation
- Multiple rule inheritance
- Module import that works with rule inheritance
- Multiple dispatch for helper methods
- Lazy implementation of OCL collections
EMFTVM is currently only available from ATL CVS, but will be included in the next ATL release (3.3). As a temporary measure, EMFTVM can be downloaded as an ATL add-on for ATL 3.1 or up from http://soft.vub.ac.be/soft/research/mdd/emftvm
The EMF Transformation Virtual Machine (EMFTVM) is derived from the current ATL VMs and bytecode format. However, instead of using a proprietary XML format, it stores its bytecode as EMF models, such that they may be manipulated by model transformations. A special EMF resource implementation allows EMFTVM models to be stored in binary format, which is faster to load and save, and results in smaller files.
Apart from the standard ATL bytecode primitives, such as modules, fields, and operations, EMFTVM bytecode includes rules and code blocks. Fig. 1 shows the structure of rules and code blocks. Code blocks are executable lists of instructions, and have a number of local variables and a local stack space. Operation bodies and field initialisers are represented as code blocks in EMFTVM. Code blocks may also have nested code blocks, which can be manipulated and invoked from its containing block. These nested code blocks therefore effectively represent closures, which are nameless functions that can be passed as parameters to other functions. Closures are helpful for the implementation of OCL's higher-order operations, such as select and collect, which are parametrised by nested OCL expressions.