The government services needed by citizens or businesses often require horizontal integration across autonomous government agencies. The information and services needed are typically scattered over different agencies in diverse formats, and therefore are not interoperable. This results in the so-called “stove-pipe” service and information paradigm, which raises a number of challenges. First, the service consumers, both citizens and businesses, face the challenging task of locating relevant services and information from a large number of documents scattered at different locations on the Web. Therefore, it is beneficial to have a system to locate and integrate available services that are tailored to individual preferences and needs according to regulations. Second, due to the fact that information is not shared among the different agencies, service consumers are required to re-enter certain data repeatedly to obtain interagency services. Service integration should allow sharing among agencies. Digital governments have been evolving with different focuses in terms of information and transaction services. The evolution has shown at least four different stages. At the first stage, with the Internet and the WWW, governments digitized paper forms and started to disseminate information with static Web pages, electronic forms, and data displays. The focus of this initial stage has been to make information digitally available on the Web. The transaction services tended to resort to off-line paper-based traditional methods (e.g., by submitting the printed form with a payment) such as by credit cards. In the second stage, governments started to provide services for the citizens by developing applications for service delivery and databases to support the transactions. The citizens and businesses can “pull down” the needed services and information through “active” interaction with individual agency Web sites separately, as in self-services. In both of these stages, the digital government efforts did not consider what other government agencies have been doing and how their services may be related to other agencies’ services. The information and service consumers need to “visit” each agency separately and actively search for information and services. The digital government up to this stage mimics the physical government, and citizens and business entities navigate digital boundaries instead of physical boundaries for complex services, such as business registration or welfare benefits. When agency interactions are needed, data and forms are forwarded in batch mode to other agencies through paper or fax, where the data is re-entered, or the digital data captured from a form is forwarded in a file via CD-ROM or a floppy disk. The streamlining of business processes within individual agencies may have been achieved, but not the streamlining of business processes across agencies. In the third stage, digital government agencies strive to provide seamless, integrated services by different agencies with sharing necessary information. The services and documents are organized such that they are easily identified and the consumers do not have to scour large amounts of information for the right ones. This stage of digital government is characterized as one-stop portal stage. In the fourth stage, the governments create digital environments where citizens’ participation is encouraged to define government policies and directions. The services up to the third stage are often enforced by government regulations and policies. These very rules and policies can be modified by citizens’ participation. In this fourth stage, digital government efforts focus on developing collaborative systems that allow collaboration among government agencies and citizens in order to reflect the constituents’ inputs. Today’s digital governments characterized by “self-service” and “one stop portal” solutions, between stages two and three, need to provide front-end (citizen-facing) tools to deliver relevant, customized information and services, and a back-end (processing) infrastructure to integrate, automate, manage, and control the service delivery. The service integrations vary according to user requirements and need to be dynamically achieved in an ad-hoc manner with personalized processes as end results.