Facebook Open Graph Semantic Markup Protocol





Another important rich snippet Microformat is the Facebook Open Graph Protocol.

In 2010, Facebook starts using the Open Graph protocol to help ensure your site’s pages are presented well in Facebook search and various interfaces

Although it is not a Searc engine semantic markup, you should not worry as you can use the Facebook Open Graph Semantic Markup Protocol simultaneously with Schema.org semantic Markups rich snippets protocol — the two do not conflict with one another.




Facebook Open Graph protocol semantic markup rich snippet schema microformating





From The Open Graph protocol 


The Open Graph protocol enables any web page to become a rich object in a social graph. For instance, this is used on Facebook to allow any web page to have the same functionality as any other object on Facebook.
While many different technologies and schemas exist and could be combined together, there isn't a single technology which provides enough information to richly represent any web page within the social graph. The Open Graph protocol builds on these existing technologies and gives developers one thing to implement. Developer simplicity is a key goal of the Open Graph protocol which has informed many of the technical design decisions.

Basic facebook open graph protocol Metadata

To turn your web pages into graph objects, you need to add basic metadata to your page. We've based the initial version of the protocol on RDFa which means that you'll place additional <meta> tags in the <head> of your web page. The four required properties for every page are:
  • og:title - The title of your object as it should appear within the graph, e.g., "The Rock".
  • og:type - The type of your object, e.g., "video.movie". Depending on the type you specify, other properties may also be required.
  • og:image - An image URL which should represent your object within the graph.
  • og:url - The canonical URL of your object that will be used as its permanent ID in the graph, e.g., "http://www.imdb.com/title/tt0117500/".
As an example, the following is the Open Graph protocol markup for The Rock on IMDB:
<html prefix="og: http://ogp.me/ns#">
<head>
<title>The Rock (1996)</title>
<meta property="og:title" content="The Rock" />
<meta property="og:type" content="video.movie" />
<meta property="og:url" content="http://www.imdb.com/title/tt0117500/" />
<meta property="og:image" content="http://ia.media-imdb.com/images/rock.jpg" />
...
</head>
...
</html>

Optional Metadata

The following properties are optional for any object and are generally recommended:
  • og:audio - A URL to an audio file to accompany this object.
  • og:description - A one to two sentence description of your object.
  • og:determiner - The word that appears before this object's title in a sentence. An enum of (a, an, the, "", auto). If auto is chosen, the consumer of your data should chose between "a" or "an". Default is "" (blank).
  • og:locale - The locale these tags are marked up in. Of the format language_TERRITORY. Default is en_US.
  • og:locale:alternate - An array of other locales this page is available in.
  • og:site_name - If your object is part of a larger web site, the name which should be displayed for the overall site. e.g., "IMDb".
  • og:video - A URL to a video file that complements this object.
For example (line-break solely for display purposes):
<meta property="og:audio" content="http://example.com/bond/theme.mp3" />
<meta property="og:description" 
  content="Sean Connery found fame and fortune as the
           suave, sophisticated British agent, James Bond." />
<meta property="og:determiner" content="the" />
<meta property="og:locale" content="en_GB" />
<meta property="og:locale:alternate" content="fr_FR" />
<meta property="og:locale:alternate" content="es_ES" />
<meta property="og:site_name" content="IMDb" />
<meta property="og:video" content="http://example.com/bond/trailer.swf" />
The RDF schema (in Turtle) can be found at ogp.me/ns.

Structured Properties

Some properties can have extra metadata attached to them. These are specified in the same way as other metadata with property and content, but the property will have extra :.
The og:image property has some optional structured properties:
  • og:image:url - Identical to og:image.
  • og:image:secure_url - An alternate url to use if the webpage requires HTTPS.
  • og:image:type - A MIME type for this image.
  • og:image:width - The number of pixels wide.
  • og:image:height - The number of pixels high.
A full image example:
<meta property="og:image" content="http://example.com/ogp.jpg" />
<meta property="og:image:secure_url" content="https://secure.example.com/ogp.jpg" />
<meta property="og:image:type" content="image/jpeg" />
<meta property="og:image:width" content="400" />
<meta property="og:image:height" content="300" />
The og:video tag has the identical tags as og:image. Here is an example:
<meta property="og:video" content="http://example.com/movie.swf" />
<meta property="og:video:secure_url" content="https://secure.example.com/movie.swf" />
<meta property="og:video:type" content="application/x-shockwave-flash" />
<meta property="og:video:width" content="400" />
<meta property="og:video:height" content="300" />
The og:audio tag only has the first 3 properties available (since size doesn't make sense for sound):
<meta property="og:audio" content="http://example.com/sound.mp3" />
<meta property="og:audio:secure_url" content="https://secure.example.com/sound.mp3" />
<meta property="og:audio:type" content="audio/mpeg" />

Arrays

If a tag can have multiple values, just put multiple versions of the same <meta> tag on your page. The first tag (from top to bottom) is given preference during conflicts.
<meta property="og:image" content="http://example.com/rock.jpg" />
<meta property="og:image" content="http://example.com/rock2.jpg" />
Put structured properties after you declare their root tag. Whenever another root element is parsed, that structured property is considered to be done and another one is started.
For example:
<meta property="og:image" content="http://example.com/rock.jpg" />
<meta property="og:image:width" content="300" />
<meta property="og:image:height" content="300" />
<meta property="og:image" content="http://example.com/rock2.jpg" />
<meta property="og:image" content="http://example.com/rock3.jpg" />
<meta property="og:image:height" content="1000" />
means there are 3 images on this page, the first image is 300x300, the middle one has unspecified dimensions, and the last one is 1000px tall.

Object Types

In order for your object to be represented within the graph, you need to specify its type. This is done using theog:type property:
<meta property="og:type" content="website" />
When the community agrees on the schema for a type, it is added to the list of global types. All other objects in the type system are CURIEs of the form
<head prefix="my_namespace: http://example.com/ns#">
<meta property="og:type" content="my_namespace:my_type" />
The global types are grouped into verticals. Each vertical has its own namespace. The og:type values for a namespace are always prefixed with the namespace and then a period. This is to reduce confusion with user-defined namespaced types which always have colons in them.

Music

og:type values:
  • music:duration - integer >=1 - The song's length in seconds.
  • music:album - music.album array - The album this song is from.
  • music:album:disc - integer >=1 - Which disc of the album this song is on.
  • music:album:track - integer >=1 - Which track this song is.
  • music:musician - profile array - The musician that made this song.
  • music:song - music.song - The song on this album.
  • music:song:disc - integer >=1 - The same as music:album:disc but in reverse.
  • music:song:track - integer >=1 - The same as music:album:track but in reverse.
  • music:musician - profile - The musician that made this song.
  • music:release_date - datetime - The date the album was released.
  • music:song - Identical to the ones on music.album
  • music:song:disc
  • music:song:track
  • music:creator - profile - The creator of this playlist.
  • music:creator - profile - The creator of this station.

Video

og:type values:
  • video:actor - profile array - Actors in the movie.
  • video:actor:role - string - The role they played.
  • video:director - profile array - Directors of the movie.
  • video:writer - profile array - Writers of the movie.
  • video:duration - integer >=1 - The movie's length in seconds.
  • video:release_date - datetime - The date the movie was released.
  • video:tag - string array - Tag words associated with this movie.
  • video:actor - Identical to video.movie
  • video:actor:role
  • video:director
  • video:writer
  • video:duration
  • video:release_date
  • video:tag
  • video:series - video.tv_show - Which series this episode belongs to.
A multi-episode TV show. The metadata is identical to video.movie.
A video that doesn't belong in any other category. The metadata is identical to video.movie.

No Vertical

These are globally defined objects that just don't fit into a vertical but yet are broadly used and agreed upon.
og:type values:
  • article:published_time - datetime - When the article was first published.
  • article:modified_time - datetime - When the article was last changed.
  • article:expiration_time - datetime - When the article is out of date after.
  • article:author - profile array - Writers of the article.
  • article:section - string - A high-level section name. E.g. Technology
  • article:tag - string array - Tag words associated with this article.
book - Namespace URI: http://ogp.me/ns/book#
  • book:author - profile array - Who wrote this book.
  • book:isbn - string - The ISBN
  • book:release_date - datetime - The date the book was released.
  • book:tag - string array - Tag words associated with this book.
  • profile:first_name - string - A name normally given to an individual by a parent or self-chosen.
  • profile:last_name - string - A name inherited from a family or marriage and by which the individual is commonly known.
  • profile:username - string - A short unique string to identify them.
  • profile:gender - enum(male, female) - Their gender.
No additional properties other than the basic ones. Any non-marked up webpage should be treated as og:typewebsite.


REMEMBER to Test the snippets on Google’s Structured Data Testing Tool (previously called the “Rich Snippet Testing Tool”)


References: 

Facebook Open Graph protocol 
OGP
Facebook Developers Page 


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