Latest revision as of 09:38, 30 November 2017

Old information
This page is not updated anymore; for more up-to-date details look at the language specification at https://www.eclipse.org/viatra/documentation/ instead.

VIATRA Incremental Query Wiki Documentation

For the query language, we reuse the concepts of graph patterns (which is a key concept in many graph transformation tools) as a concise and easy way to specify complex structural model queries. High runtime performance is achieved by adapting incremental graph pattern matching techniques based on the Rete algorithm.

We believe the average programmer using EMF models will like VIATRA Query for the following reasons:

• declarative queries can be evaluated over EMF without manually traversing the models,
• complex interrelated constellations of EMF objects can be easily formulated as a graph pattern,
  • the language is expressive and provides powerful features such as negation or counting,
  • graph patterns are composable and reusable,
  • queries can be evaluated with great freedom, i.e. input and output parameters can be selected at run-time,
  • some frequently encountered shortcomings of EMF’s interfaces are addressed:
  • easy and efficient enumeration of all instances of a class regardless of location,
  • simple backwards navigation along all kinds of references (even without eOpposite)
  • finding objects based on attribute value,
• the incremental query evaluation mechanism offers a significant performance boost when frequently querying complex structural patterns with a moderate amount of modifications in-between (e.g. during continuous validation),
• from the declarative representation of queries, pattern matcher code is generated which can be distributed as Eclipse plug-ins with very few dependencies.

VIATRA Query User Documentation

• Developing Incremental Model Queries using the VIATRA Query Tooling
  • Getting started with Query Development
  • A Short Introduction to the Query Language
  • Advanced topics
    • Advanced pattern language constructs (incl. recursion)
    • Finding query evaluation hotspots (since 1.0.0)
    • Query Test Framework
    • VIATRA Query Debugger Tooling (since 0.8.0)
    • RETE Visualizer
    • Local Search Debugger Tooling
• Using the VIATRA Query Runtime library
  • API documentation
  • Local Search Support
  • Base Indexer
  • Advanced API features
  • Run once querying API documentation
  • Headless (standalone) execution of VIATRA queries and unit tests
• Query language extensibility
  • Pure whitelist (since 1.0.0) for custom code in check() or eval()
  • Custom aggregation operators (since 1.4.0)
• Examples
• VIATRA Query in CI Environments (Maven artifacts) (since 0.8.0)
• Frequently Asked Questions