schema.org microdata: Do as schema.org says, or as Google says?

Question

When adding microdata to my sites, I use the vocabulary at schema.org.

At the moment, I use http://schema.org/SoftwareApplication to markup software. Since the format is a bit underspecified at schema.org (for instance, what is the difference between url, downloadUrl, and installUrl?), I also had a look at the Google page about this vocabulary.

That made me sad.

It turns out that schema.org and Google use two incompatible versions of the 'same' vocabulary. Some differences:

• fileSize is given in kB according to schema.org, but in bytes according to Google.
• operatingSystem at schema.org is called operatingSystems at Google.
• applicationCategory at schema.org is called softwareApplicationCategory at Google. <rant>...and Google says that the value 'must be one of the supported software application types', but the link to these types is broken.</rant>

Now, to be fair, Google claims that their format is an 'extension' of the schema.org format (but don't you need a new itemtype URL then?), but surely no extension can redefine existing property names (like fileSize).

What should webmasters do about this? It feels like the right thing to do is to follow schema.org. Is there any consensus on this topic?

(I just came up with a hypothesis: Maybe schema.org is the current version, and the obsolete Google pages were written before schema.org was created, and has simply been left untouched (possibly forgotten) since then?)

Answer 1

applicationCategory at schema.org is called softwareApplicationCategory at Google. ...and Google says that the value 'must be one of the supported software application types', but the link to these types is broken.

Have a look at http://www.w3.org/wiki/images/b/b3/Schema.org-SoftwareApplicationsV2.pdf

Thing > Intangible > Enumeration > SoftwareApplicationType 
● GameApplication (action, arcades, etc) 
● EntertainmentApplication (music, sports, TV) 
● BusinessApplication (productivity tool, accounting, finance, tax) 
● MultimediaApplication (audio/video player, consumer photo/video editor) 
● DeveloperApplication (compilers, debuggers) 
● DriverApplication (OS drivers) 
● EducationalApplication 
● HealthApplication 
● TravelApplication 
● FinanceApplication (accounting, finance, tax) 
● SecurityApplication 
● BrowserApplication (web browser, RSS reader, browser add-on/plugin) 
● CommunicationApplication (email , VOIP application) 
● DesktopEnhancementApplication 
● DesignApplication (graphic design, pro audio/video, modeling, CAD/CAM) 
● HomeApplication (decoration, landscaping, DIY) 
● SocialNetworkingApplication 
● UtilitiesApplication (system tools, utilities) 
● ReferenceApplication (books, reference)
● SportsApplication 
● ShoppingApplication 
● MedicalApplication 
● OtherApplication