The Screen

In order to view the beautiful pictures delivered from the source, you need a TV set. In my childhood we had a monochrome Cathode Ray Tube (CRT) TV set, a huge box, incredible heavy, full of electrical components. Produced in Russia, its handle broke and we had nippers near the TV set in order to switch the channels (they were switched by rotating the handle). The next TV set we had could reproduce color but had approximately 12″ screen size. Its channels could be switched using small buttons. In the nineties, the time of big CRTs begun. A normal person could effort a 30″ CRT and of course it had a remote control. I saw my first plasma screen on an exhibition in Germany – I was thrilled by its relative small depth in comparison to a CRT. But the plasma screens of the nineties were heavy, consumed about 400W and had about 8 fans, which were pretty loud. Finally, the time of LCDs began and now the technology seem to be one of the main technologies in the market of TV sets. It is difficult to find a store selling CRTs in Germany.
A LCD screen has several parameters. Some of them are just attempts of vendors to deliver technology to the market before it is really ready. A good example of this is contrast ratio: in fact no sane person want to know what contrast ratio is delivered by the TV screen, it should be just enough. Other parameters are saying something about the quality of the picture you can see e.g. the resolution of the screen. The resolution of 1920 x 1080 pixels is the most common resolution of current Full HD (1080p) TV screens.

Source of Recorded Video

After everyone bought hundreds of movies on the Video Home System (VHS) cassetes, the industry changed the technology from a tape to a disc. The Digital Versatile Disc (DVD) killed the VHS during a decade in order to be killed by the new standard called Blue Ray Disc (BD). To explain the difference in one sentence: DVD delivers only PAL quality (576p, or 576 lines), BD delivers 1080p (1080 lines). A remarkeable difference, but not all movies profit from a higher quality. So take a chance to buy old movies, where the higher resolution doesn’t play a role on DVD, before you have to pay for an expensive BD.

Source of Broadcasted Video

In addition to high quality recorded video source, you can receve a broadcast program. In old days, the television broadcast was analog. Since two years, the analog broadcast is being scaled back in Germany and is being replaced by the Digital Video Broadcast-Terrestical standard (DVB-T). Current DVB-T standard is not designed to deliver HDTV, but eventually it will be replaced by DVB-T2. There are two other ways to deliver the video program: cable or satellite. The corresponding standards are called DVB-S (for Satellite) and DVB-C (Cable). Both standards can deliver digital pictures in HDTV (1080p). Most offers of channels in HDTV are encoded and not free. Still, there is a reason for fees that every German having a TV set has to pay: the public channels ARD and ZDF will be transmitted in HDTV starting in 2010, arte broadcasts the HDTV already, since the middle of 2008.

The Sound

In order to complete the high-quality cinema-like felling in the living room, the sound system should support something like 5.1 dolby surround. This inlcludes a set of four boxes, a center loudspeaker, a subwoofer and an dolby-surround amplifier.

Conclusion

I watched a wonderful movie on arte tonight. The beautiful pictures deliverd by a Full HD 1080p screen and the nice music from processed by the complex logic of the digital amplifier. It was Charlie Chaplins’ “Modern Times”, created by his genious in 1936 in USA: a restored black-white silent movie. A real masterpiece…

It is impressive, since I was not searching for Eclipse, but the Big Brother was able to establish the semantic link between Sublipse and Eclipse and look for Eclipse & p2. It turns out that p2 is Pentium II and Eclipse is the Fujitsu Siemens Notebook.

For all non-geeks among us: Eclipse is a the famous software platform and integrated development environment built on top of it. P2 is the system for provisioning and installation of components inside of Eclipse. Eclipse is the example for the open-source development and is available free of charge.

My talk was focussed on the basics of CNF. After some slides on Why, What and How, I moved on to a live coding demo and coded a small CNF view inside of an trivial RCP. Everithng worked fine, until the launch – I misspelled one id in the plugin.xml, and had to resign and showed the prepaired result instead of the hacked one. If you want to read more, check out the TechJava report.

The reason for my first home Linux installation was to provide access to the Internet from multiple home computers. It was at time of analog modems and 10Mbit ethernet over coaxial cable. As soon as high speed Internet over ISDN was available (and cheap enough), I changed to that emerging technology. The basic setup of the Internet gateway was a computer with a bunch of IPChains scripts on it. Later ISDN was replaced by ADSL, but in essence the gateway remained the same.

Around seven years ago, I had two servers running at home: a gateway and a fileserver. I never invested in server hardware at home. The hardware was the result of my administration activities – old crappy buggy stuff, bought on ebay, gathered by some customers during replacements etc… On the gateway machine (the smaller one), the self-configured IPTables scipts provided NAT firewalls rules, fetchmail gathered mail for all family members and saved it to a local quickmail installation (I had sendmail running too, but editing m4 files is not my passion), a DNS using Bind 8/9 provided local domain address resolution and DHCP was responsible for configuration of the local computers. I also played around with HylaFax and ISDN4Linux based Phone Answering Machine. It was really funny to have e.G. personalized (caller-id-based) messages for different people. The fileserver machine (the most performant one) was running Samba in PDC mode, and had (at most) two SCSI-U controllers and a doozen old cheap small loud SCSI drives connected to them. In addition, ProFTP server, Apache HTTP Server, MySQL, CUPS (for printing) were also running on the fileserver. I’ve never been a fan of compile-your-linux-yourself approach, but used SuSE distributions. I also played with Fli4L – a German mini Linux to be booted from a floppy. The advantage of that approach was the absence of a hard drive in the gateway, which is very silent then. Later, I also experimented with IPCop, a special Linux platform for the Internet gateway/firewall. The recent two-server-installation consisted of two Intel Pentium III machines, which consumed about 400 Watts of power. The fileserver machine had six SCSI hard drives and four IDE drives in it and weighted about 20 kg.

The first big technological change was the introduction of smart Internet-routers/Gateways by different vendors. So, I got rid of a self-configured NAT-firewall and shifted DNS/DHCP to my fileserver (renaming it just to server). The reason for that is – most DNS/DHCPs built into Internet gateways are silly and can not be compared to Bind name-daemon or ISC DHCP. The advantage of usage a standard device (like e.G. Fritz!Box) is a silent, low-power solution (one device for all instead of 3-5).

From that point on, I started to adjust the number of services running on the server. The first change was a shift from quickmail to postfix and IMAPd (from POP to IMAP). The next change was – from IMAPd at home to IMAP at Google. Now, I’m a massive user of Google Mail – both for gmail.com address and my own domains (see Google for your Domain offer). The next service, that became obsolete on the server was the printing subsystem. It was replaced by a small network printserver (first one from Lexmark, now HP JetDirect). But the real reason for elimintation of it is the independence of CIFS protocol for printing.

The next technological change was the introduction of cheap NAS (Network Access Storage) devices. This allowed to replace 10 old hard drives with one modern located in a small device with 15W power consumption and ethernet socket (like e.G. Buffalo LinkStation). As a result I could move the storage away from the Primary Domain Controller (PDC). The PDC is still needed, otherwise the lookups in “Network Neighborhood” could continue for minutes. In addition, I added some services needed for software developement: especially CVS and SVN repositories and Bugzilla.

As a result I could switch of the last Pentium III off and start up a small Pentium II (a 50W consuming Compaq). It runs DNS, DHCP and Samba for purposes of system infrastructure and Apache HTTPD (with PHP, DAV and Pearl), MySQL, SVN, CVS. In fact, I’m reasoning on buying a SSH access on a Internet-hosted machine (e.G. by domainfactory) and installation of Bugzilla and SVN there. In doing so, I’m following the trend from “IT infrastructure as property” towards “IT as a service”. I was also reasoning about getting rid of the NAS at home, but this is only reasonable with really high speed Internet.

• What: Eclipse DemoCamp + Eclipse Stammtisch
• Where: Hotel East, Hamburg ( Simon-von-Utrecht-Str. 31, 20359 Hamburg, Germany)
• When: May 25th 2009, 18:00-21:00 (official part)

I’m attending. If you want to attend, make sure you find a minute to write you name down in EclipseWiki.. If you want to read more, look at the original post at TechJava…. See you on the DemoCamp.

You can find more on that in post just published by me on TechJava…

• SANY – Syntax Analyser for TLA+ specifications
• TLC – A modelchecker / simulator for TLA+ specifications
• TLATeX – LaTeX typesetter for TLA+

The PCal Translator is not covered in this post and will be introduced in a separate post, together with PCal language.

SANY

SANY is a syntax analyser for the TLA+ language. The purpose of it is to check the syntax of the specifications (including some static semantics) and provide the errors to the user. As all of the TLA+ Tools currently available, SANY is a command line tool and reports the errors back to the console. In fact SANY is a front-end of the compiler (lexer, parser, semantic analyser). In order to invoke it call:

java -cp %TLA_CLASSPATH% tla2sany.SANY fowler.tla

SANY is currently the only official way to find out, if the specification complies to the rules of the TLA+ language. It is absolutely a non-trivial program, basically because of the complexity of the TLA+ grammar. Especially, the parts responsible for precedence-checking and level-checking are use complex algorithms.

TLATeX

As noticed by Peter, the language has a special notation, which could appear cryptic to someone who see them for the first time. The reason for this is pretty simple: TLA+ is a mathematical language and the ASCII version TLA+ is very close to LaTeX notation of the corresponding mathematical symbols. Everyone, who is aware of LaTeX can read and write TLA+ easily. For others, the ASCII specification can be translated into a TeX file and rendered to a DVI, PS or PDF. A piece of specification of the secret compartment ( download full TLA file), looks as follows rendered as PDF ( download as PDF).

The question of WYSIWYG editor support involves not only rendering of the symbols (that is the easiest part), but the input of these symbols by the user. Therefor, the ASCII version of TLA (we could also speak about ASCII encoding), which uses at least in certain areas know LaTeX-like encoding is a convenient way for editing specs. There are attempts to create WYSIWYG formula editors, which work pretty good, but the these have to be used with a mouse and the input speed is not comparable with the typing plain LaTeX.

The usage of TLATeX is simple. After the installation of TLA Tools, the TLATeX is invoked from the command line:

java -cp %TLA_CLASSPATH% tla2tex.TLA -shade fowler.tla

The tool produces a .tex file which can be included in the existing document. It also can be rendered directly if LaTeX is installed on machine.

TLC

TLC is a model checker for TLA+ specifications. It’s main purpose is to find bugs in specifications. For this purpose it creates the state-space described in the specification and checks the properties (safety and liveness). In contrast to SANY which is responsible for syntax and static semantics check TLC is checking the dynamic semantics of the specification. At this point I only want to mention, how TLC is invoked. I’ll cover some advanced TLC topics in the later posts:

java -cp %TLA_CLASSPATH% tlc2.TLC fowler.tla

In addition to the TLA file, containing the specification itself, TLC requires a CFG file, which describes the model, that has to be checked. This fact appears unusual to the TLA beginners, but is easy to clarify. The specification of the system is a description of systems behavior. To a given behavior, several models can be constructed. In addition, specifications can be combined resulting in bigger specifications. In the specification, there are no real differencies between actions: (Init, TypeInv, CloseDoor or Spec). Thus, the user has to specify which of these actions are actulally the parts to check.