Enterprise Server (ES) is typically used to create internal integrations that perform data-level or function-level integration between enterprise applications. For example, when an order is taken in Siebel, send appropriate data to the XYZ warehousing system and the PeopleSoft financials.
Integration Server (IS) is typically used to create business-to-business integrations using the FLOW language (created using the IS Developer tool). For example, when a loan application is submitted, order the appraisal from ABC Appraisal Services by posting the appropriate XML document over an HTTPS connection.
webMethods 6.0 does blur the lines between the two somewhat, but primarily because the architecture for creating Enterprise adapters changed with this release. In the future, adapters will be created using the webMethods IS Adapter Development Kit and will execute inside a webMethods Integration Server using the webMethods Adapter Runtime (wMArt) package. A single IS server can host multiple resource adapters or lightweight IS serves can be installed on or near the server where the resource (application) is running.
When the product releases (around the end of March at this writing) only the JDBC adapter and possibly one other adapter will be available using this new approach. Therefore, companies who need to use an adapter that does not yet exist in the new architecture will need to use the existing Enterprise adapter and create their integrations using the version 5.0 development tools (Enterprise Integrator). This will be the case until the new versions of the adapters are all released (and performing well). See the adapter roadmap document on the webMethods Advantage site for first quarter adapter plans: http://advantage.webmethods.com/cgi-bin/advantage/main.jsp?w=0&s=3223822579&targChanId=-536881230
There is another adapter roadmap slide or two from the Integration World presentation that should be available somewhere on WM Advantage, but I couldn’t find it quickly.
Going forward you will create the integration business logic for an adapter purchased from webMethods or created using the WM ADK using Developer to write Flow or Java services.
Clear as mud?