WebGME Transformations

This is an experimental transformation language for defining model transformations within WebGME.

Overview

This contains a model transformation language as a metamodel and the corresponding code to perform the transformations. Transformations output JSON nodes which can then be instantiated, if desired. (This may not always be the case if used for visualizers or plugins, for example.)

Transformations contain a series of steps (or ordered rules) which are applied in sequence to the input model. A step contains both an input and output pattern. (The output pattern is sometimes referred to as a structure since it can be instantiated and isn't as abstract as a pattern.) The input model is matched against the input pattern to find valid assignments for all nodes, pointers, and attributes in the pattern.

For each assignment to the pattern elements, the output pattern is created. The output pattern can contain references to the input pattern. These are resolved to the node/attribute/pointer assigned to the element in the input pattern and are different when multiple valid assignments are found.

When creating transformations with complex relationships, it can be helpful to first create nodes and then defined relationships between them in a subsequent rule. To this end, the origin pointer can be set from an element of an output pattern to the element it corresponds to in the input pattern. This designates that the output node corresponds to the matched node from the input pattern. To refer to this newly created node in later steps, the MatchedNode element can be used.

Quick Start

This is a webgme app and can be run accordingly. First, run MongoDB locally and install the dependencies with npm install. Then run npm start in the project root to start the server.

Code Organization

The main code layout is given below:

• src/common/ModelTransformation.ts: Class used to perform a model transformation from an instance model of a transformation (and input model) in WebGME.
• src/common/TransformationObserver.ts: Observer to track an input model and transformation definition. Callback will be called with the new model whenever either is updated.
• src/engine/crates/engine: Pattern matching engine (written in Rust).
• src/engine/crates/engine-js: Engine with wrappers and API for compiling to wasm.
• src/plugins/ApplyModelTransformation: Plugin to apply a model transformation and download the output model as JSON.