Portal integration pools one or more Web resources that are relevant to a user into a thin-client layer such as a Web browser or a portal application.

A portal approach gives users freedom to rearrange the information presented to them and integrate it in creative ways. You aggregate content from multiple sources and adapt it from potentially different formats to render reports. Flexibility makes portal integration a strong solution for the candidate-screening Web site.

The drawback of portal integration is that any benefit your users receive by mixing data together to make their decisions is done manually. Other users looking at the same portal must perform this ad-hoc integration. For example, the staffing firm exemplified in this article must reach the decision from the portal of whether to hire, so little integration needs to be redone.

Data integration combines one or more resources at the source (sometimes within the database or a data integration layer sitting above one or more databases) before exposing them to clients over the Web. You aggregate information resources into views when you extract them from one or more sources. Most data integration takes place in or close to the collection of data, so that a uniform schema for that data becomes immediately available to higher layers of the application. The cost involved in combining data and ironing out any semantic differences that might exist between sources of that data is paid for only once.

The disadvantage to data integration is that it usually takes place close to where the data is kept, and frequently the consumer has some control over that data. For instance, in this article's staffing firm example, it would be unfeasible to obtain access to the data sources of every governmental agency and educational institution to integrate the data needed. Instead, data integration is frequently the value-added proposition of providers that license, aggregate, and resell collected information.

For more information on patterns valuable for building SOAs, consult Microsoft's Patterns & Practices guidance Web site.