More block Generalization examples: Home entertainment system

Many, many years ago, before there were DVDs or Blurays, before there were USB sticks or interweb downloads, there was a technology called the 'VHS player' that used magnetic tape, cassettes for which you could rent from a shop with movies recorded on it, or which you used to record shows from the TV to watch later.

Note how block VhsPlayer is abstract; that's because although most VHS units could play media, they could (mostly) also all record.

The block UsbDrive - which might also have been made abstract, but for now is concrete - is both a RemovableRecordingMedium and a UsbPeripheral, which pattern is sometimes called a "mix-in" (and is NOT an anti-pattern in SysML).

A quick word on Block naming conventions

Webel Best Practice offers some alternatives here. The blocks DvdPlayer and VhsPlayer could have been named DVD_Player and VHS_Player consistent with:

Webel Best Practice: When using acronyms in names of Classifiers either treat them as a word 'TlaLikeThis' or suffix with an underscore 'TLA_LikeThis', except at the end of the name 'LikeThisTLA' is admissable.

Or HardDrive and UsbDrive could have been named Drive_hard and Drive_USB consistent with:

Webel Best Practice: If using "French style" post-adjective naming in English use a trailing underscore after the noun and before the adjective or qualifier: Vin_rouge, Cable_digital. Can be combined with TLA acronyms: Player_DVD.

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Indicating inherited features: Home entertainment system

Notes

[ASSERTION]{STRONG} When domain modelling with SysML, Generalization, inheritance, and even multiple inheritance are not "evil" and can be used relatively freely. We are not doing code-oriented Decorator patterns - an implementation choice - we are doing domain modelling!

[NAMING, POLICY]{STRICT} DO NOT use spaces in Property names or Class/Block names! If you want to communicate familiar names of elements within an organisation use a custom stereotype and tagged values (such as 'aka')!

[NAMING, POLICY]{STRONG} Use 'UpperCamelCase' (a.k.a. PascalCase) names for Classifiers such as UML Classes and SysML Blocks) to avoid confusion with 'lowerCase' Property names [see however special naming conventions for acronyms and SysML contract and flow Blocks]

[NAMING, POLICY]{STRICT} When using acronyms in names of Classifiers either treat them as a word 'TlaLikeThis' or suffix with an underscore 'TLA_LikeThis', except at the end of the name 'LikeThisTLA' is admissable.

[CONVENTION, NAMING]{STRONG} If using "French style" post-adjective naming in English use a trailing underscore after the noun and before the adjective or qualifier: Vin_rouge, Cable_digital. Can be combined with TLA acronyms: Player_DVD.

[POLICY, TIP]{STRONG} Webel: SysML: Always consider including an abstract (sometimes intermediate) base Block in your domain modelling Generalization hierarchy.