A well-constructed UML Sequence Diagram can be a valuable tool on many levels in the EA process.  A simplified one can act as a process flow diagram with activities mapped against people and systems.  See a real-world example from a colleague.  You can also use sequence diagrams for detailed technical documentation, especially useful to show messaging within an application or between systems.   See an example at Kallokain's blog.

How do sequence diagrams fit into my ADM?

Short answer, depends on the type of the diagram.  Example 1 would be a good foundation for working through the Business Architecture steps of your ADM.  That is, to figure out a few key questions:

• How do people map against key systems?
• How do processes/activities map against key systems?
• Where are opportunities to consolidate or enhance key systems to enable more efficient resource deployment (people) and/or processes?
• Where are the opportunities to automate processes/activities?

Example 2 is more suited for looking at Applications Architecture.  A few key questions here are:

• How does messaging relate to application control mechanisms?
• Are there any high-use routines where we need to think bigger about scalability?
• Where are the risk points in a system in terms of fault tolerance and failover?

What are some tools for making sequence diagrams?

There are many tools for drawing sequence diagrams, including the ones on Wikipedia's comprehensive list at http://en.wikipedia.org/wiki/List_of_Unified_Modeling_Language_tools.  For the old school folks who want to use pencile and napkin, the Object Management Group keeps the formal specification of UML at http://www.omg.org/spec/UML/2.2/.

I will say, my favorite tool is WebSequenceDiagrams.com which keeps it simple and also gives you an option to download and install locally, if you like.Blogged with the Flock Browser