OCL/Articles

Articles and Presentations

2011 / Indigo

• "Enrich Your Models With OCL", Edward Willink and Axel Uhl, EclipseCon Tutorial, 2011

The utility of the Object Constraint Language for modeling within Eclipse has increased dramatically in the last few years, so that Eclipse OCL is now useful for everyday modelers rather than just advanced Java programmers.

This tutorial will demonstrate to existing EMF users how OCL in isolation can enhance their models and how the Eclipse support is re-used within advanced model transformation tools.

The tutorial will first introduce OMG's OCL language and its capabilities, then show how OCL can be embedded within Ecore to support validation and evaluation of dynamic EMF models without using genmodel at all. This part of the tutorial will introduce the OCLinEcore text editor that supports the combined development of OCL and Ecore, the CompleteOCL editor that supports complementary development of OCL and the the Interactive OCL Console that supports interactive evaluation.

Models developed during the Ecore integration part of the tutorial will be elaborated during the rest of the tutorial to demonstrate how model representations can be transformed using model to model transformations and then presented in human-friendly fashion by model to text transformations.

The model to model transformation section of the tutorial will provide a brief overview of OMG's QVT Operational Mappings language and Eclipse's M2M/QVTo tooling, while developing the running example with particular emphasis on the use of OCL to perform complex navigations and queries.

The model to text transformation section of the tutorial will provide similar brief overviews of OMG's M2T language and Eclipse's M2T/Acceleo tooling. The running example will be elaborated to showing more extensive use of OCL.

OCL supports the formulation of very compact queries that it is useful to practice. The tutorial will demonstrate this style of working by providing regular opportunities to configure and use some OCL facility with additional challenges for those participants who find the basic examples too easy.

• "Efficient OCL Impact Analysis", Thomas Goldschmidt and Axel Uhl, presented at Heidelberg University, 2011

• "Aligning OCL with UML", Edward Willink, "OCL 2011, Workshop on OCL and Textual Modelling", TOOLS 2011

OCL is widely used by UML and other languages to constrain metamodels and perform evaluations on models. Unfortunately no OCL 2.x specification has ever been aligned with any UML 2.x specification. This lack of alignment makes some OCL compliance points such as XMI interchange unachievable. This paper describes how introduction of an OCL Pivot Meta-Model and clear exposition of the Values package may provide a solution to the alignment and a variety of other specification issues.

• "Modeling the OCL Standard Library", Edward Willink, "OCL 2011, Workshop on OCL and Textual Modelling", TOOLS 2011

OCL is widely used by UML and other languages to constrain metamodels and perform evaluations on models. The OCL specification is the result of diligent but time-constrained human endeavor and so contains many inconsistencies, most of which are relatively easy to ignore as obvious typographical mistakes. However the need to ignore minor discrepancies undermines rigorous treatment of more significant issues. The minor issues can be substantially eliminated by autogenerating the specification. This paper provides early community visibility of proposed solutions to a variety of issues that arose while developing a model for the OCL Standard Library that forms the core of the OCL specification.

2010 / Helios

• "Enrich Your Models With OCL", Adolfo Sanchez-Barbudo Herrera, Axel Uhl and Edward Willink, Eclipse Summit Europe Long Talk, 2010

The utility of the Object Constraint Language for modeling within Eclipse has increased dramatically in the last few years, so that MDT/OCL is now useful for everyday modelers rather than just advanced Java programmers. This long talk is focused on both non-OCL users and advanced OCL users so that any kind of audience may learn how OCL can enhance your (meta-)model definitions and how OCL forms the foundation of advanced modeling technologies such as Acceleo and QVT.

In the first part of the talk, focused on modelers who have yet to discover OCL, you will get a short introduction to the OMG's OCL language and its main capabilities. Then you will learn how OCL can be embedded within Ecore to define constraints for validation, operation bodies for evaluation and derived features for initialization of EMF models (both dynamic instances and those from generated Java classes using "genmodel"). A presentation of the OCL Interactive Console will be used to help the user to alternatively write and validate their OCL constraints.

Finally, focusing on the advanced OCL audience, you will learn about ongoing work to exploit Xtext to provide an enhanced OCL development environment and of OCL to define its own editors and language semantics. Extensive use of OCL within OCL mandates a dramatic performance improvement requiring a flexible Java code generator for an efficient first evaluation of an OCL expression and an impact analysis to avoid redundant re-evaluation following a model change.

• "Re-engineering Eclipse MDT/OCL for Xtext", Edward Willink, "OCL 2010, Workshop on OCL and Textual Modelling", MODELS 2010

The current tooling used for the Eclipse OCL project uses an LALR parser generator. Enhancing the tooling to support editing motivated a migration to exploit the inherently model-driven characteristics of Xtext. This paper summarizes the experiences of that migration, identifies the many benefits and discusses a few changes in implementation approach that were required. Objective performance and size comparisons between the old LALR and new Xtext approach are provided.

2008

• "Querying UML Models using OCL and Prolog: A Performance Study" presented at MoDeVVa'2008 by Joanna Chimiak-Opoka et al.
  (OCL expressions used in the study are available online at the OCL Editor web page in the Library Concept / Concrete Syntax section)

2007

• OCL Tools: Status and Perspectives by Miguel Garcia and A. Jibran Shidqie
• OCL Compiler for EMF by Miguel Garcia and A. Jibran Shidqie
• How to process OCL Abstract Syntax Trees by Miguel Garcia
• Implementing Model Integrity in EMF with OCL by Christian W. Damus
• EclipseCon 2007 tutorial "Effective Use of the Eclipse Modeling Framework" by Ed Merks et al.