About ten years ago, a really interesting exodus took place in the software development world. Architects and developers everywhere ran away, screaming in some cases, from building applications for the desktop to building pure web-bases solutions. Why? One simple reason: Web applications are way easier to deploy and maintain.

This stampede to the data center created some new problems, however:

• The browser, in many ways, is not the avenue to create rich user experiences
• Offline capabilities in "occasionally connected" applications went away completely
• Data and functionality is the desktop silo was simply relocated to a web silo

And thus it has been for the past decade.

The Return of the Client
Ray Ozzie talked a lot about software plus services in his keynote address at Microsoft MIX a couple of weeks ago. Ray's vision is a world where key application functionality is written and deployed as hosted services in the cloud that can be consumed by many different application end points running on a multitude of different platforms. This model of "many pieces loosely coupled" allows you access critical data and functionality whenever you need it, wherever you happen to be.

I've always been a big fan of the client application, and have spent the better part of my career writing these types of applications. This concept of software on the computer or device significantly leveraging hosted services has been a major component of my work lately. However, in talking to people about it, I get a fairly consistent comment back when discussing this:

I don't want to go back to building fat clients again. What a pain.

This got me thinking: Is this whole S+S thing moving us backward? Are we going to end up with the same deployment and maintenance problems we had before the web came along?

The "Thinner" Client
In a world of software and services, we need to think about the role of the client-side software differently than we did before. Without a doubt, local software will need to be smarter than your pure web applications ("thin" clients). Likewise, many of the features that we would normally need to build into a completely local piece of software ("fat" client) are going to be managed by services in the cloud.

As this kind of application isn't "fat" or "thin," I propose the concept of the thinner client -- fatter than a thin client, but thinner than a fat client.

The thinner client is a fully functional piece of software that can:

• Provide a compelling user experience because it can leverage the normally untapped processing powers of the client machine and fully take advantage of the strengths of the local OS software
• It can manage and organize data online or offline
• It provides users a piece of mind from a security perspective, sharing non-sensitive data online while locking-down sensitive data on the local machine
• Manage and automatically install software updates via services
• The innate extensibility of services facilitates multiple client "heads" for any particular application -- desktops, mobile devices, cell phones, game consoles, you name it

Thus, the thinner client manages only the work it needs to on the client machine, leaning on the hosted services for the rest of the required functionality.

Real World Thinner Clients at Work
The simplest example I can think of to illustrate this architecture is the subject of my last post: Twitter. At its core, Twitter is a hosted service that provides a communication hub, allowing people to post updates on what they're doing any time they like and people who are interested to receive those updates in near real time.

To start using Twitter, you create an account for yourself on the web site. From that point on, there is a multitude of different applications you can use to access the hosted service. As I write this, I have twhirl running on my machine pulling updates down for me. From my cell phone, I can either access a mobile friendly version of the Twitter web site or use TinyTwitter, a client application written for Windows Mobile on top of the .NET compact framework. And these are only a few examples. If you really want to get a feel for how many channels there are to distribute content from Twitter, just have a look at the Twitter Fan Wiki.

The core functionality of Twitter is exposed in its hosted services. This single architectural decision enables large scale extensibility of content delivery channels. These thinner clients offload the work of managing the stream of communications to hosted services and focus on delivering content in a way appropriate to a specific platform.

The Thinner Client In Practice
While Twitter certainly won't every be accused of being a business system, it certainly provides a solid example of how this architecture can grow and extend to meet many different user needs. Imagine this type of architecture flexibility in the line-of-business applications you're working on today.

Imagine you're working for a manufacturing company. A sales person is at your biggest customer's office and they make the decision to place a large order with you and have a very aggressive timeline for delivery. The sales person has a mobile device on which he/she can enter the order information. The data is entered, but their wireless Internet connection is not available right then and there, so the mobile application persists the data locally. As the sales person leaves the customer site, the Internet connection becomes available and the application automatically pushes the data to a service hosted in your company's data center. This service sends the data into the sales system and then forwards it on to the ERP system which queues up the order for production line processing. Production floor personnel, viewing the order via a PC based application consuming the same set of services, can then see the priority of the order and act accordingly.

At the same time, sales managers at your company are getting notifications on their cell phones alerting them to this major deal. At this point, they can send feedback via the system back to the sales person on site, generate reports to get the information to upper management or notify key personnel in the manufacturing part of the company to raise visibility of the ongoing activity.

And there's a good chance that all of this has happened while the sales person is still in their car on their way back to the office.

Hosted services in this case provide a continuity of experience for users at all client endpoints. Client applications are consuming a consistent set of functions and data based on need, priority and the role of the end user. Centralization of service-level functionality provides one version of the truth, instilling confidence that everyone involved in the process if fulfilling the order is working with the correct information in to correct portion of the workflow.

With the ability to leverage computing cycles on the fringe, run effectively in an occasionally connected world and automatically update themselves when new updates and patches become available, thinner clients represent an extremely viable alternative to pure web applications. They leverage what is best about client-side applications with the agility of the of the web to provide an engaging and valuable experience to users.

"Thinner" is the new "fat."