Interoperability is a term used to describe the ability of a device to interact with another device. An iPhone or rich sensor can be seen as a device with a high amount of interoperability, whereas an old fashioned refrigerator could be seen as only having the capability to interface with the wall in order to receive electricity. Unlike a phone, the number of devices and protocols the fridge can interact with is very low.
Objects with greater levels of interoperability are key to ubiquitous computing. Over time, the web has emerged as an interface that smart sensors can hook into in order to connect with other sensors, data sources and users. Though many at research institutions such as PARC and SRI expected ubiquitous computing to appear much sooner, the emergence of the web as the largest technological interface for data pushed the emergence of ubiquitous computing further into the future.
Ambient and pervasive ubiquitous computing cannot exist without a large network of data connectivity. PARC Researcher Bo Begole writes that, "the network revolution alleviated some of the key issues that Ubicomp addressed"...as "information access expanded beyond what was immediately physical at hand hard drives, removable disks, flash memory), to vast information repositories on the network".  The web had to form before the era of ubiquitous computing could finally begin.
Interoperability invites opportunity. In 1994 Sheldon Renan wrote that "anything that is connected always has more opportunity than anything that isn't. Making it easy for things to work together is the fastest way to lower the cost of anything".
Interoperation in Traditional vs. Ubiquitous Computing
In Ubiquitous Computing For Business, Begole points out the traditional computing problem of Transfer, in which "separate computing components should be able to get information from each other without requiting manual transfer". In traditional computing, this refers to computing components inside a computer. In ubiquitous computing, transfer refers to all components that exist anywhere in reality. If the three big problems of traditional computing are performance, storage and transfer, then the big problems of ubiquitous computing are control, overload and interoperation, which Bo Begole defines as "who owns the information and how the can control who can access it when, how to find pertinent information, and how data from one system can be used by a complementary device or service". In ubiquitous computing, transfer morphs into interoperability.