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Cross Media (also known as cross-media, cross-media entertainment, cross-media communication, transmedia) is a media property, service, story or experience distributed across media platforms using a variety of media forms. It refers to the journey or linkages across devices and through forms and is most evident in branded entertainment, advertising, games and quest based forms such as Alternate Reality Games where there are a range of dependencies between the media placed across devices and fragments there-of. There are potentially four main categories  or levels of cross-media:
Cross-media 1.0 – Pushed. 
The same or minor variations of content placed or pushed onto different platforms in different forms. E.g.: A minor re-edit of the audio from a TV programme for a podcast or a script adapted for a website and in its simplest form exactly the same content delivered on multiple platforms such as mobile, TV and broadband web. The user in this case could create their own cross-media linkages by watching half of the episode on mobile and the rest on broadband. This level does not have strong cross-media triggers but may promote the same content on another platform.
A good simple example of this is the world first Forget The Rules which was a weekly short form drama delivered simultaneously on TV, Broadband Web and 3G mobile.
Cross-media 2.0 – Extras. 
This is content produced alongside a main production and delivered on different platforms from the main production. This 'extra' cross-media content is naturally different from the main property and not necessarily dependent on it - temporally or editorially. For example it could be a mobile video-captured behind the scenes of a feature film, destined and delivered in segments on the mobile phone. It could be a flash game strongly based on a radio drama or a book back story delivered through posters in train stations. The most obvious incarnation is the ubiquitous 'making of' feature that may be delivered only via video web portals.
A good recent example is the various transformations of a property called Thursday's fictions. This started as a stage production, was published as a book, then was turned into a surreal dance film, and more recently had a Second Life presence created for it. Each version played to the strengths of each platform but none were dependent on each other contextually or from a user journey perspective.
Cross-media 3.0 – Bridges. 
The truest form of cross-media where the story or service structure is specifically authored to drive the audience using strong Call-To-Actions, across media devices to continue the journey. The content placed on the other platform is critical to staying in touch with the experience and the narrative bridges tease you towards investigating or moving to another media form/platform. Obvious examples include a TV show that ends suddenly and gives you a URL to explore more. It may be an SMS that teases and points you towards a live concert in a city square which then leads you to a TV show, then to a podcast then to subscription emails. The trigger, or bridge, is the critical component of this in motivating the cross-media action.
A very strong example of this is the 30 second Mitsubishi Super Bowl XXXVIII TV ad which showed objects being thrown out of a truck in front of two trailing race cars, an accident avoidance test. It paused on a cliff-hanging moment (as two cars were thrown out) and invited the audience to go to SeeWhatHappens.com. Millions did.
Cross-media 4.0 – Experiences. (transmedia) 
An aggregation of the first three levels this is also where the content is distributed across many platforms in a non-linear way and is producer ‘hands-off’- in that they have created an environment, much like a game, that the participant/s ‘lives’ inside of, following their own path and therefore personalizing the experience. A cross-media 4.0 property is co-creative, collaborative play with the audience across many devices, which evolves and grows a life of its own. Story Environments are a key part of the mix in driving the inhabitants of the 'experience' across devices or around the narrative fragments (whether advertorial, entertainment or dramatic). Although likely to be heavily authored the cross-media triggers and invitations are part of the experience in terms of the audience creating their own bridges. The best examples of this are Alternate Reality Games and it incorporates elements of the first three levels but is likely to be dynamic in that producers will have to be constantly bridge building in response to where audiences are travelling.
Crossmedia communication 
Crossmedia communication is communication in which the storyline will invite the receiver to cross-over from one medium to the next. Making it possible to transform from one-dimensional communication (sender -> receiver(s)) to multi-dimensional communication (sender(s) <-> receiver(s)). Good crossmedia communication will enhance the value of communication: The level and depth of (message) involvement will be more personal and therefore more relevant and powerful. Advantages can be: 1. Financial profits can be gained through equal or decreasing costs for the same or better communication effects with single medium communication. It is possible to shift costs for communicating from the sender to the receiver if the story is attractive enough for the receiver to want to interact with it. 2. Deepening relations between story (teller) and "receivers" on several levels of communication
Examples are: Pop Idol, Big Brother, Popstars the Rivals
Some context to the "crossmedia field" The shifting balance in the powers between sender - medium - receiver, makes for communication to start crossing over from: - Only senders (Formerly Known As MassMedia) sending out communication to 'receivers' (Formerly Known As Audience) reacting to, interacting with, participating in and co-creating with the information (story) presented to receivers. Receivers become senders, senders become receivers.
- Hayes. G. "Cross-Media What Audiences Want" Personalizemedia 2006
- Veglis,A., Cross Media Communication in newspaper organizations, in Poulymerakou, A., Pouloudi, N., Pramatari, K. (eds) 4th Mediterranean Conference on Information Systems, Athens, Greece, September 25–27, 2009, CD-ROM, ISBN 978-960-98566-7-6.
Further reading 
- Signer, Beat: Fundamental Concepts for Interactive Paper and Cross-Media Information Spaces, May 2008, Hardcover, 276 pages, ISBN 3-8370-2713-9 (10), ISBN 978-3-8370-2713-6 (13)
- Wedia White Paper www.wedia.fr
- Crossmedia Communication
- cross-media content production and protection, see Axmedis
- Cross Media Finder Portal by using Axmedis open model and tools
- Crossmedialog (Dutch)
- CrossmediaLab (research group)
- Cross-Media Entertainment
- PICNIC 06 - Cross Media Week
- Reynolds DeWalt Cross-Media Blogs
- Cross Media Development Lab Australia
- 1st Intl. Cross Media Interaction Design Conference
- TSS Cross Media Group
- 4Dconcept XMS - Cross Media CMS
- Evado - Cross Media CMS
- Wedia XMS - Cross Media CMS
- Tristit - Cross Media
- MXM:MediaCrossMedia - Cross Media Conference Series