Activity and Sequence diagram

What is an Activity Diagram:
Activity diagrams are kind of flow chart which represent the flow from on activity to another or visual presentatio of actions. these are similiar to flow charts. These diagrams are used in business process modelling. These diagrams can be defined as work flow behaviour of system IT.

Parts of activity diagram:
Actvity diagrams consists of following notations and symbol
start point, action flow, object, decision or branching, Gaurds, Synchronization, time event, merge event, swimlanes, joint and fork and end point.

Advantage of Activity Diagram:
These diagrams are easy to understand by Stakeholders and analyst.
These are useful to depict work flow.
allows multiple condition and actors through swinlanes

Disadvantages of activity diagram:
can be used in small projects.
difficult to identify actors in the same work flow.
does not have details of object behavior.

What is an Sequence diagram:
Sequence diagram or event diagram is a way to view and validate different runtime scenarios. this an interaction diags where one can find how objects with another object and in what order.

Parts of Sequence diagram:
Messages.
Lifelines.
self message.
synchronus and asynchronus.
reply or return.

Advantages of Sequence diagram:
sequence diagrams are useful tools for logic problems early on in the design process.
problems can be narrowed.
can be used in documents for dynamic view of system design at different levels.

Disadvantages of Sequence diagram:
takes lot of time to make diagram reasonable in sync with the code.
cannot represent the every condition in a diagram.
costlier.