ness model. Both offer plumbing that enables companies to build applications. Both are designed for computer-to-computer interactions and so have no advertising model— because there are no eyeballs involved in the interactions. It is up to the companies to invent business models that can leverage the Web-services plumbing.

Web services reduce the costs of publishing and receiving information. Today, many services offer information as HTML pages on the Internet. This is convenient for people, but programs must resort to screen-scraping to extract the information from the display. If an application wants to send information to another application, it is very convenient to have an information-structuring model—an object model—that allows the sender to point to an object (an array, a structure, or a more complex class) and simply send it. The object then “appears” in the address space of the destination application. All the gunk of packaging (serializing) the object, transporting it, and then unpacking it is hidden from sender and receiver. Web services provide this send-an-object / get-an-object model. These tools dramatically reduce the programming and management costs of publishing and receiving information.

So Web services are an enabling technology to reduce data interchange costs. EDI (Electronic Data Interchange) services have been built from the very primitive base of ASN. 1. With XML and Web services, EDI message formats and protocols can be defined in much more concise languages such as XML, C#, or Java. Once defined, these interfaces are automatically implemented on all platforms. This dramatically reduces transaction costs. Service providers such as Google, Inktomi, Yahoo!, and Hotmail can provide a Web-services interface that others can integrate or aggregate into a personalized digital dashboard and earn revenue from this very convenient and inexpensive service. Many organizations want to publish their information. The World Wide Telescope is one example, ³ but the example is repeated in biology, the social sciences, and the arts. Web services and intelligent user tools are a big advance over publishing a file with no schema (e.g., using FTP).

APPLICATION ECONOMICS

Grid computing and computing-on-demand enable applications that are mobile and that can be provisioned on demand. What tasks are mobile and can be dynamically provisioned? Any purely computation task is mobile if it is written in a portable language and uses only portable interfaces—WORA (write once run anywhere). Cobol and Java promise WORA. Cobol and Java users can attest that WORA is difficult to achieve, but for the purposes of this discussion, let’s assume that it is a solved problem. Then, the question is:

What are the economic issues of moving a task from one computer to another or from one place to another?

A computation task has four characteristic demands:

• Networking. Delivering questions and answers.

• Computation. Transforming information to produce new information.

• Database access. Access to reference information needed by the computation.

• Database storage. Long-term storage of information (needed for later access).

The ratios among these quantities and their relative costs are pivotal. It is fine to send a gigabyte over the network if it saves years of computation, but it is not economic to send a kilobyte question if the answer could be computed locally in a second.