GLOSS - A GLSP Model Server on the Smalltalk Platform

Can Smalltalk serve as a modern platform for graphical modelling tools — and what does implementing the GLSP protocol reveal about its strengths and limitations?

These slides accompany the paper: GLOSS - A GLSP Model Server on the Smalltalk Platform

The Graphical Language Server Protocol (GLSP) extends the widely adopted Language Server Protocol into the graphical modelling domain, enabling web-based modelling clients to communicate with back-end model servers in a loosely coupled, standardised way. Existing reference implementations exist in Java and TypeScript, but no Smalltalk implementation existed at the outset of this project. Graham McLeod and Gareth Cox set out to build one — christened GLOSS (Graphical Language Object Server in Smalltalk) — using Pharo, and to evaluate how well GLSP maps to the architecture of the authors' existing EVA graphical modelling environment.

The paper documents the design and implementation of GLOSS, tracing the decisions made and challenges encountered, and provides a detailed architectural comparison between the GLSP approach and the EVA/GM system developed over two decades at Inspired. The comparison is striking: the Smalltalk implementation of a multi-model-type server supporting the full GLSP protocol runs to under 4,000 lines of code, compared to over 58,000 lines for the Java reference implementation of a single model type. Beyond code volume, the paper identifies nine concrete limitations in the current GLSP protocol — including the absence of model type support, server-side symbol management, and item reuse across models — and proposes specific remedies for each.

For practitioners working on modelling tools, architecture repositories, or graphical language design, this paper offers both a working proof of concept and a substantive critique of an emerging standard.

Originally published as a conference paper by Graham McLeod and Gareth Cox at the International Workshop on Smalltalk Technologies (IWST 2024), Lille, France, 2024.

Designing an Effective Graphical Modelling Language

How can visual modelling languages in enterprise architecture be designed to genuinely communicate meaning — rather than confusing or alienating the stakeholders they're meant to serve?

These slides accompany the paper: Designing Effective Visual Languages for Enterprise Modelling and a video of the presentation is available here: Design and Support of Modelling Languages for Effective Graphical Representation, Analysis and Communication

Graphical models are everywhere in enterprise architecture — yet a persistent gap exists between the effort invested in building them and the value they deliver. Models are too technical for business audiences, too homogenous to highlight what matters, or presented in formats that stakeholders simply cannot parse. When practitioners try to bridge this gap by converting rigorous models into PowerPoint slides or Word documents, they sever the connection to the underlying repository — destroying integrity, reusability, and currency in the process.

This paper presents the research programme Graham McLeod is pursuing at the University of Duisburg-Essen, supervised by Prof. Ulrich Frank, to address these problems at a foundational level. The research draws on human visual cognition, semiotics, information encoding theory, the Physics of Notations, and the emerging field of polymetric diagramming — a technique that modifies visual symbol properties such as size, colour, and shape to reflect underlying data, enabling pre-attentive processing and rapid identification of important patterns in large, complex models. The proposed contributions include extended theory for visual notation design, a meta-meta model supporting multiple visual languages over the same semantic model, and a layered tool architecture enabling runtime adaptation of models to purpose, audience, and medium.

For enterprise architects, this research points toward a future where modelling tools can produce representations genuinely suited to a CFO, a process owner, or a technical architect — from the same underlying repository, without manual translation.

Originally published as a doctoral consortium paper by Graham McLeod in the PoEM 2018 Doctoral Consortium Proceedings (CEUR-WS Vol. 2234), Vienna, Austria, 2018.