Gemstone/S Application Example – HbbTV Playout System

The last two weeks we had two elections here in Germany – one in Schleswig-Holstein and last weekend in Nordrhein-Westfalen in Düsseldorf.

Television Tower next to state parliament in Düsseldorf

As mentioned in an earlier posting we already used Gemstone/S as our database during the election for the broadcaster SWR and we played out results and graphics for an internet based application. The model is defined using PUM, source code is created for Topaz, Sencha ExtJS and Python3.

This weekend we did a similar application for the broadcaster WDR (Westdeutscher Rundfunk), but not for their Internet presence, but for an HbbTV hybrid add-on service during their program on sunday and 14 days later (so its still available via their WDR TV channels).

Persons at the broadcaster were able to enter results via an browser based data-enter application – and the results were stored in Gemstone/S and transferred to the system producing the animated TV graphics. Application as usual – API oriented, browser based.

Input Application written in Sencha ExtJS

The structure of the application was pretty similiar to the one of last autumn – main logic is located in the Gemstone/S database, several independent topaz processes are inserting election results, preparing graphical repesentations of the results and even do an automatic publication of the results without interaction.

The system is managed via a browser based UI (written in Sencha ExtJS), communicating via an API with the database. External applications were otherwise written in Python3.

Management Software written in ExtJS

The system was actually running in parallel on two different systems at some hosters – producing the same results independently.

Current HbbTV at the WDR television broadcaster

The end-user application (running on the TV sets) was written in “low-level” Javascript (WITHOUT any larger libraries like jQuery) to make is runnable on even the most slowest TV set available on the market :-)))

Final Results shown in HbbTV

Voters moving from one party to another

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PUM – Overall Application Structure

Sometimes its not clear, where PUM is targeting – a graphic may show this much better. In this graphics one can see the general application structure we have used with PUM and the other languages against Gemstone/S database in several projects so far.

The parts in dark blue are actually in production usage, Android and Java have been tested in small application and the practical tests for iPhone are still missing.



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PUM – Adding JavaDoc support

With the version today I added initial JavaDoc support in the generated source code.

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PUM – Updating VASmalltalk Generator

When looking around the generators I noticed, that I forgot to made several changes to the VASmalltalk generator (e.g. remove the needs for cookies).

Therefore the runtime had to be changed and I changed the created methods for VA to look them more like the ones I created for the mainstream languages.


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PUM – Dolphin7 – just for fun

When working on PUM today I started by random Dolphin7 and looked around a bit and then decided to do initial work for a code generator.

Dolphin7 is quite a nice target, because it is Smalltalk and it can produce native Windows application.

The code generator I’ve written today so far creates the whole class structure in a pac-format file. There is a base pac-file holding the base runtime, but that’s it.

The problem with Dolphin7 here is the missing of several supported stuff:

  • json-support, datetime wih timezone

We will see, how difficult this can be …

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PUM – Adding C# as a supported language …

Another language added to PUM – though in an early state, but the first program has been coded on an Android device via C# and Xamarin and it got its result …

The language binding was mainly driven by the design of the Java binding I wrote last weekend – but due to the fact, that I focused now on Xamarin I decided to go to implement the binding by creation “Portable Class Libraries” under .NET.

That was a topic I’ve never done before … and it became quickly a miracle … The PCL based libraries are libraries based on available .Net code on the selected target platforms and the intersection of available methods and attributes can become very strange.

Looking for solutions in the Internet is more or less useless – most of these published solutions are based on the normal .Net 4.x and this has far more classes than available in the PCL platform.

But somehow I made my way to implement a http request and even got an answer from that. The biggest problem became the selection of a suitable json library – all libraries I tried did not work. Even the Newtonsoft.Json library (10.0 with various architectures) had problems with the various platforms and well I was nearly up to a point to leave this project, when I found an older Newtonsoft.Json 7.0 library at Xamarin and I used this one and it worked.

Due to the Xamarin way I only support the async-API … that means, that all calls are executed asynchronely to the program – this seems to come from the mobile platforms – and was introduced later in the desktop .Net 4.x system also.

Now I have to become familar to this new development platform, polish the libraries a little bit, try out iPhone and that stuff.

After Java and Xamarin/C# most of my “wished” languages are available under PUM in a more or less (:-)) stable way:

  • Java, C#, Python 3, Sencha ExtJS, Electron (ExtJS), VASmalltalk

That means, that from all these languages I can now access my Gemstone/S based API-oriented systems.



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PUM – Adding Java to the supported languages

This weekend was a Java weekend. Never really worked before with that language, but a customer wanted a Java interface for our product, so I had to implement a Java-8 generator to PUM.

More or less three days were needed (including learning all that Java usual stuff). I decided to use gjson as the JSON support library and on Saturday the first test application could be coded and it worked – and lot of time was needed to persuade gjson to do its job.

The structure is pretty simple – one need a base runtime jar file offering the needed http support and json support. PUM generates the code for another jar file containing the model and the main ApiClass.

Still more work is needed to make exception handling more comfortable and add more documentation to the source code.

After that success I started to rewrite the C# generator part to remove all the swagger code I generated and needed and make the C# part actually a clone of the Java part in terms of the structure. Here I use Json.Net as the supported Json library.

The main idea behind that is to get a proof of concept, that we would be able to write apps for Android or iPhones – using the Xamarin framework now available with VisualStudio 2015.



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