We're talking a lot about "Mobile" solutions in the industry, but the umbrella that this moniker casts has become far too big to be useful and doesn't represent any particular scenario subset that's useful for planning services for "mobile" devices. Nearly every personal computing scenario that consumers encounter today is "mobile".

This post is a personal perspective on "mobile" applications and how applications that run on devices labeled under this umbrella really enable a range of very different scenarios, and do require a different set of backend services, depending on the core scenario.

From this perspective, I present a taxonomy for these experiences that may be helpful with regards to their relationship to cloud services: Mobile, Outside, Inside, and Attached.

  • Mobile only applies to all scenarios where I am literally mobile. I'm moving.
  • Outside applies to all scenarios where I'm away from my office or my house, but at rest.
  • Inside applies to all scenarios where I'm at the office or at the house, but potentially roaming.
  • Attached applied to all scenarios where the experience is immovably attached to a physical location or device, appliance, or other machinery.


As soon as I get into my car and drive, my $700 phone is not really all that useful. Things will beep and ring and try to catch my attention, but they do that without respecting my physical world situation where I probably shouldn't pay much if any attention.

That said – the phone does integrate with my car's entertainment system, so that I can listen to music, podcasts, and Internet streams and the phone functionality also integrates for a hands-free experience. It also reads text message to me out loud as they arrived when the phone is paired with my car. That all happens because the OS supports these core functions directly.

In the case of my particular car, a 2013 Audi A6 with MMI Touch and Audi Connect services (I'm not at all meaning to be boasting here), the phone/entertainment system has even its own phone SIM, so all my phone gets to contribute is its address book and the music/audio link for playing songs from the phone. Text messages and phone communication and the car's built-in navigation features including getting live traffic data is all natively supported by the vehicle without needing the phone's help.

To help making sure that the traffic data is accurate, the vehicle sends – today; this isn't science fiction – anonymous motion information, so-called "floating car data" telemetry into a data pool where it gets analyzed and yields real-time information about slowdowns and traffic jams complementing stationary systems.

If you need to catch my attention while I am mobile in the sense of 'in motion' you either have to call me and hope that I choose to pick up and am not talking to someone else already, leave me a voice mail, send me a text message and hope I'll call back or, otherwise, wait. A text message will reach me right in the central dashboard display of my car.

If you send me a Twitter message or send me something on Facebook or send me an Email I most certainly won't see it until it's safe for me to take my eyes off the street – because it is much less targeted and not integrated in the experience that my personal safety depends on in that situation.

When I'm walking on the Microsoft campus or I'm at an airport in line to board a plane, it's very similar. You can try to reach me via any of these channels, but it's not too unlikely that I'll make you wait when the immediate circumstances demand my attention. Boarding that plane or getting to the next building in time for a meeting with 20 people while it's raining outside is likely of higher urgency than your message – I'm sorry.

A 'mobile' experience is one that supports my mobility and the fact that my primary focus is and must be elsewhere. It can augment that experience but it must not attempt to take center stage because that ought not to be its role. The "My Trips" app for TripIt.com on Windows Phone is a near perfect example of an experience that is truly tailored to mobility. The app doesn't make me ask questions. It knows my itinerary and anticipates what info I will need the next time I look at the live tile.

When I'm arriving at an airport, it will have looked up my connecting flight and will have sent a notification or repeatedly try to send one to fill the Live Tile with information about the connecting flight status and gate information. I don't even have to open the app. If there are critical disruptions it will send me a Toast notification that comes with an audible alarm and vibration to help getting my attention.

Avis, the rental car company, does the same thing via email and also their app for me since I'm a "Preferred" customer. Just before the scheduled pick-up time, which they can also adjust since I give them my flight info, I get a timely email with all the information I need to proceed straight to the stall where my rental car is parked and will find that within the last handful of emails as my plane lands. I proceed to the rental care facility, get into the vehicle, and I get the rental agreement slip as I exit the facility presenting my driver's license. No need to ask for anything; the system anticipates what I'll need and it excels at that.

The phone's calendar is obviously similar. It will show me the next relevant appointment including the location info so that's available at a glance when I just look at the phone while I'm walking to another building; and it will provide the most recent updates so if the meeting gets moved between rooms as I'm on my way then I'll see that reflected on the lock screen.

All these mobile experiences that I'm using today as I'm traveling, share that they are decoupled, asynchronous, often time-driven, and message based. I don't ask for things. I answer to and react to what needs my urgent attention and otherwise I will observe and then "get to it" as I truly have time to focus on something other than getting from A to B and being mobile. Mobilility is driven by messaging, not by request/response.


Being on the road, doesn't literally mean to be driving all the time, of course. Once I sit down and indeed start interacting with a device in order to read email, go through my other messages, read/watch news, or get some work done, I am still outside of the office or the house, but I am yet not on the move. I am at rest in relatively safety and can pay closer attention to the interaction with my information device.

The shape of that interaction differs from the pure mobile experience in that I commonly ask questions and interact with the device, with focus on the device experience. That includes everything from browsing the news, to researching with Wikipedia, watching training videos, to enjoying a movie. Listening to podcasts and/or radio is also one of those experiences even if we're often doing so while being on the move, i.e. walking or driving, as we're instantly able to turn our attention to more important matters as needed – like a nearing ambulance – if we're managing the audio volume as appropriate for the situation.

The outside experience is one where I can indeed get at most of my data assets, as much of it is readily accessible from anywhere since it's stored on the cloud or networked and accessible via VPN. Whether the device I am using to access that data is connected via 3G, LTE, WLAN, or wired Ethernet, and whether the screen is 5" or 27" is largely a question of what sort of an experience I'm looking for, and how big of a device I want to carry to where I'm going.

For many, if not most consumers, this outside experience is often the preferred interaction mode with their devices – and when they own only a single device it's largely indistinguishable from the Inside experience that I'll expand on in the next section. They sit in a cafe or elsewhere comfortable with connectivity, make notes, write email, hatch plans, capture snippets of their life in photos or videos and share them with friends through Instagram, Twitter, or Facebook.

For me, the Outside experience is however quite different from the Inside experience because it's constrained in two key ways: First, while and when connectivity is available, it's commonly either metered or it's provided on someone else's terms, for free or even paid, and that means I don't get a say on the bandwidth and quality and the bandwidth may be seriously constrained as it is, for instance, in most hotels.

What Outside also often means is that connectivity is sparse or non-existent. If I'm traveling and outside the country where I have my primary data contract, I will pay a platinum-coated-bits premium for data. Therefore I find myself Hotspot-hopping quite a bit. Outside may also mean that I'm going away from the core coverage zones of wireless networks, which means that I might quite well end up with no reliable access to network services because I'm either in a remote valley or inside the Faraday-Cage hull of a ship. It might also mean that I am in a stadium with 52,000 other people who are trying to use the same set of cell towers – which is the case about every two weeks for me.

Second, what I am connecting to is a shared network that I cannot trust, which is not well suited for easy discovery and sharing scenarios that rely on UPnP/SSDP and similar protocols.

From an infrastructure perspective, apps that focus on Outside experiences work best if they can deal with varying quality and availability of connectivity, and if they are built to hold and/or access data in a way that is independent – for better and worse – of the scope and sandboxing provided by the local network that I'm connecting to. Thus, Outside experiences are best suited for using cloud-based services.


The Inside experience is much like the Outside one but with the key difference that I either directly own the environment that I'm connecting into or that I at least have reason to trust the owners and anyone else they allow to connect to the environment. That's true for my home network and it's also true, even though with a few caveats, for the office network.

The Outside/Inside split and a further differentiation of Inside into work and home environments is also what the Windows Firewall uses to categorize networks. The public, outside networks are on the lowest trust level, domain networks are a notch higher, and private networks are most trusted.

The experiences that I use on my Inside network at home are indeed different from the experiences I use when Outside. Xbox Smart Glass is a pure inside experience that pairs my mobile device with my Xbox as a companion experience. Xbox connects to my Windows Media Center to make my DVB-S2 SmartCard tuner available to in the guest room, I have a remote control on my phone for my Onkyo A/V receiver, I have IPTV apps with which I can tune into HDTV streams available on my Internet service, I use file sharing to access my multi-TB local photo archive.

A great Inside-experience needs services that are very similar to those of Outside experiences, including state-roaming between devices, and even more so support for seamless multi-device "continuous client" experiences – but they are not necessarily cloud-bound.


Some of the latter Inside experiences, especially the photo archive, are on the brink towards being Attached scenarios. Since I'm shooting photos in RAW and video in 1080p/50, I easily bring home 30GB+ or more from a day out at a museum or air show, and I tend to keep everything. That much data develops quite a bit of gravitational pull, meaning to say that it's not easily moved around.

What's not easily moved around, at all, are experiences that depend on a particular physical asset that is located at a particular place. The satellite dish at my house is something I need to be close to or go to (in the network sense) in order to get at content that is exclusively delivered via that channel. It also, has to be decoded with that one precious smart card that I rent from the Pay-TV provider.

If I had surveillance cameras and motion sensors around the house (I'll let you speculate on whether I really do), those cameras and sensors are location locked and I need to go to them. I can conceivably take a WLAN hub and my Xbox when I go on a vacation trip (and some people do) to make an Inside experience at a hotel room, but I can hardly take the satellite dish and the cameras.

In the business world, even when interacting with consumers, there are plenty of these immobile experiences. An ATM is a big and heavy money safe designed to be as immobile as possible that is equipped with a computer that controls how much cash I can take from that safe. A check-in terminal at an airport makes sense there as a shared experience because it gives me a printout of a document – the boarding pass – that I can use to document my authorization to travel on a particular flight. That's convenient, since paper doesn't run out of battery.

What's particularly noteworthy is that some attached experiences, such as the huge center screen in Tesla Motors' Model S, are attached and inseparable from the larger context, and yet fulfill a mobility role at times – and at other times they function like an outside appliance.

We encounter "attached" experiences while we are mobile, but they're stationary in their own context. That context may, however, be mobile if the attached experience is an in-flight entertainment system or an information terminal on a train.


The Mobile, Inside, Outside, Attached terminology may be a tad bit factual and dry, but I believe it's a useful taxonomy nevertheless. If you have a set of catchier monikers I'm all ears. Let me know whether you find this useful.