Category Archives: Software Development

Margaret Hamilton and another approach to software development

November 23, 2016Software Development, Women in EngineeringRichard Herz

I was interested to learn about the work of Margaret Hamilton, who was awarded the Presidential Medal of Freedom yesterday. As a young woman, she led a team that designed the flight control software for the Apollo moon landers. This period was during the early days of computer programming when software design practices were just starting to be invented. Hamilton developed a theory and methodology for “design before the fact” of fault-free and fault-tolerant, real-time software control systems. The class of systems considered are asynchronous, discrete-event systems. This includes chemical batch process scheduling and control. Our web apps simulate continuous processes. Design Before the Fact contrasts with the development strategy we use, as outlined in my last post, but we will learn from Hamilton’s work.

Also at the ceremony at the White House yesterday, Grace Hopper was posthumously awarded the Presidential Medal of Freedom. She was an early pioneer in computing, invented the first software compiler, and popularized the idea of machine-independent programming languages.

Also see the blog post about other women engineers who were key figures in the moon landings.

Web Labs – our development practice

November 5, 2016HTML5, Software Development, Web LabsRichard Herz

The goal of our Web Labs is a toolbox that enables development of interactive web simulations or “labs,” and a set of labs built with this toolbox. Our development practice is as follows.

First, Get something up on the screen. Often this involves finding an example on the web and modifying it. Don’t spend a lot of time designing and thinking before something simple gets running. We believe that it is better to get something useful running than it is to have a beautiful plan and theory in development but nothing working to show for your time.

Second, repeat the following:

Add functionality.
As we observe repetition of code and see patterns developing, generalize the code. Have the objective of maximizing code in libraries and minimizing code needed to build new labs.
As we observe patterns developing in the user interfaces, refine the design of a user interface guideline that is simple and consistent between labs in order to speed development of new labs and speed user comprehension when entering new labs.
As we have time or run into problems 😛 read and learn about Javascript and CSS and design principles and try to incorporate better practices.

The most recent versions of the Javascript code are the first two labs listed at the Web Labs tab. The other experiments work but have code that was developed at an earlier stage of this software development process.

23 years of Reactor Lab and interactive simulations for active learning

September 6, 2016Interactive Learning, Reactor Lab history, Software DevelopmentRichard Herz

Reactor Lab is a pioneer in developing interactive simulations for active learning. This is a screenshot of an experiment in the Lab in March 1993, when the Lab was a single HyperCard stack. The screenshot was taken after it was converted to a LiveCode stack to keep it alive and operable on today’s computers. Click on the image to see a larger version.

Here is the same experiment in today’s Reactor Lab.

A brief history of the development of Reactor Lab through 2006 is available at LiveCode Journal. The article refers to Revolution, which was LiveCode’s previous name.

Fabrik – early visual flow based programming tool

September 1, 2016Flow-based programming, Software DevelopmentRichard Herz

In an earlier post, I wrote about flow based programming (FBP). Recently, I ran across Fabrik, which was one of the first visual tools for FBP. One inspiration for Fabrik was Show and Tell.

In chemical engineering we wire, or rather pipe, visual components together in application-specific software tools to design chemical processes (see Resources, COCO Simulator here) and process control systems (Matlab Simulink).

“Fabrik – A Visual Programming Environment”
Dan Ingalls, Scott Wallace, Yu-Ying Chow, Frank Ludolph, Ken Doyle of Apple Computer.
presented at ACM, OOPSLA 1988 Conference Proceedings
http://web.archive.org/web/20080511202219/http://users.ipa.net/~dwighth/smalltalk/Fabrik/Fabrik.html

“Fabrik is a visual programming environment – a kit of computational and user-interface components that can be “wired” together to build new components and useful applications. … A kit is a set of primitive components, together with a framework for connecting the components to do new and interesting things…. The kit approach has been around for a long time, manifest in the subroutine libraries of the last three decades. However, the ability to browse through, and experiment with the available components was extremely primitive, owing to the textual orientation of underlying computing environments during those early years. … With the advent of iconic user interfaces, nontechnical users — those not trained to appreciate invisible objects and connections — are able to work concretely (by pointing at an image) with data and functional components.”

Women in engineering, a pioneer

August 25, 2016Interactive Learning, Software Development, Women in EngineeringRichard Herz

“The unbelievable life of the forgotten genius [Katherine Johnson] who turned Americans’ space dreams into reality” http://www.businessinsider.com/katherine-johnson-hidden-figures-nasa-human-computers-2016-8

“Throughout her education, she says she succeeded in part because she was always asking questions — even when people tried to ignore her, her hand stayed up.”

Trailer for upcoming movie about Katherine Johnson, Hidden Figures: http://www.foxmovies.com/movies/hidden-figures

Flow-based programming

June 11, 2016Flow-based programming, Software DevelopmentRichard Herz

I recently discovered the Now page and work of Henri Bergius on flow-based programming (FBP). He is developer of NoFlo and lead developer of FLowhub. NoFlo (node.js flow…) is a Javascript tool for FBP, and Flowhub is a graphical development environment for FBP. FBP was invented in the late 1960’s at IBM by J. Paul Morrison.

FBP makes a lot of sense. As far as application-specific apps, see the chemical process simulators COCO, Aspen Plus, and even Reactor Lab’s Division 1, Lab 6, Reactor Networks. Although lacking a graphical programming interface, our web apps have code structured with a similar metaphor of independent objects sending messages to each other, as do the dynamic simulations in Reactor Lab. This metaphor makes writing, expanding, and maintaining dynamic simulations easy.

A screenshot of Reactor Lab’s Reactor Networks is shown here, with a screenshot from the Flowhub clock example below it. Click on an image to see full-sized version.