A symposium

When: October 4th 2019.

Where: CWI, Science Park, Amsterdam.

Attendance: Free with registration.


In the 50s, when the first programming languages were designed, computers cost millions, and relatively, programmers were almost free. Those programming languages therefore reflected that relationship: it didn't matter if it took a long time to program, as long as the resulting program ran as fast as possible.

Now, that relationship has been reversed: compared to the cost of programmers, computers are almost free. And yet we are still programming them in direct descendants of the programming languages from the 50's: we are still telling the computers step by step how to solve the problem.

Declarative programming is a new approach to applications. Rather than describing exactly how to reach the solution, it describes what the solution should look like, and leaves more of the administrative parts of the program to the computer.



10:00 Registration and coffee.


XForms, a Tutorial

Steven Pemberton

One of the few declarative programming languages available is XForms, this month celebrating its tenth anniversary in its current instantiation. It is a W3C standard, and despite its name is not only about forms. Large projects, at large companies such as the National Health Service, the BBC and Xerox, have shown that by using XForms, programming time and cost of applications can be reduced to a tenth!

This tutorial introduces XForms, and shows several amazing applications that can be written in only a few dozen lines.

Steven Pemberton chaired the W3C HTML working group for a decade, and still chairs the W3C XForms working group.



13:30 Registration and coffee.

14:00 - 16:00 Lectures

Chair: Leonie van der Voort

Declarative vs Procedural

Steven Pemberton

An introduction to the concept of declarative programming.

Steven Pemberton is a researcher affiliated with the CWI. Amongst other technologies, he co-designed ABC, the programming language that Python was based on, and web technologies such as CSS, HTML, XHTML, and XForms. He was chair of the W3C HTML working group for a decade, and still chairs the XForms working group.


Implementing XForms using interactive XSLT 3.0

O'Neil Delpratt and Debbie Lockett

Saxon-Forms is a (currently) partial XForms implementation developed using Saxon-JS, an XSLT 3.0 run-time written purely in JavaScript. Designed for browsers the mechanics of the XForms implementation such as actions are implemented using ‘interactive' XSLT 3.0 extensions available with Saxon-JS, to update form data in the (X)HTML page, and handle user input using event handling templates.

O'Neil Delpratt joined Saxonica from a research project at the University of Leicester in 2010. He is a co-developer of the Saxon product, with specific responsibility for Saxon on .NET and Saxon/C for C/C++/PHP/Python languages. Before joining Saxonica, he completed his post-graduate studies at the University of Leicester. His thesis title was “In-memory Representations of XML documents”, which coincided with a C++ software development of a memory efficient DOM implementation, called Succinct DOM.

Debbie Lockett joined the Saxonica development team in 2014 following post-doctoral research in Mathematics at the University of Leeds. Debbie has worked on performance benchmarking, the implementation of XQuery 3.1 features, and on developing the tools for creating Saxonica's product documentation. She is now the lead developer for Saxon-JS.

Are we still Open Source? Dilemmas for a new XML Database

Adam Retter

Over the last 5 years many NoSQL vendors have relicensed their software, and the landscape is only becoming more tumulous with several vendors recently playing a licensing game which is akin to Musical Chairs. Developing a new NoSQL database is no small feat, and we must eventually choose some sort of license for our users. We examine what is driving the licensing changes in the wider database community, how they apply to a new entrant to the marketplace, and ultimately ask the question, are we still Open Source?

Adam Retter has been a core contributor to the Open Source eXist-db Native XML Database for 14 years, he was also an invited expert to the W3C XQuery Working Group and helped standardise XQuery 1.0, 3.0, and 3.1. Adam founded the EXQuery project, and developed the RESTXQ framework for XQuery. Recently, Adam has been developing FusionDB a new multi-model NoSQL database which also supports XML natively.


Declarative Health: cityEHR

John Chelsom

A multi-billion pound project to provide a national distributed patient-record system for the British National Health Service failed. One person, John Chelsom, recoded it using declarative techniques, and it now running in several hospitals.

Dr. John Chelsom has worked for over 30 years in the field of Health Informatics. He qualified with a degree in Engineering Science from the University of Oxford and a PhD from City University, London, where he studied the application of artificial intelligence in medicine.

In 2010, he started the Open Health Informatics research programme at City University, London, looking to address the causes of failure of the National Programme for IT. This research led to the development of the open source cityEHR – an ontology-based health records system, based on open standard, interfaces and development practices. cityEHR is now deployed as an operational EHR in several hospitals in England and is used for teaching students in health informatics.


Views from the past

Lambert Meertens

The Views project was an outgrowth of the ABC project -- the programming language that gave birth to Python. Views was specifically an effort to design a programming environment for the ABC programming language. Its main shortcoming may have been that it was ahead of its time. The Views system has been characterized as a browser avant la lettre; I will argue that it was much more than that.

Lambert Meertens became fascinated with computers at the age of 15, when he realized that there was no limit to the possibilities of computers but for the limitations of human imagination. This fascination has lasted to today. Enabling the general public to use computing technology productively and creatively has been a major motivation of his research.


16:30 - 17:30 Reception

With a speech from Lynda Hardman.


Attendance is free, with registration.

Contact: Susanne van Dam,