What is Correlation Step?

Ans:correlation are the one that are used to make some relation between objects
like in bpm suppose u r collecting some idocs and after colecting some idocs u bunch them and send it to receiver then u need to define a corelation variable which will collect the idocs on the basis of this corelation variable.

Can anybody tell me what is trex and how it is related with xi?

Ans:TREX is a product from SAP for searching and classifying large collections of documents. TREX stands for SAP NetWeaver Search and Classification (TREX) finds information in both structured and unstructured data.
TREX is a like a search engine which provides SAP applications to search structured and unstructured data.And it can read the images for the searching query.

What is the purpose of using context object in IR?

Ans:Context Object is simply pointer to a specific XML tag. if you want to simplify your delopment you can define Context object for some fields and use the context objects. many message types come with their own context objects.

What are the Roles of an XI Architect-?

Ans:1) Get the Functional Specification/Business Requirments.
2) Set up the Procedures/Process.
3) Give the solution Roadmap.
4) Design the Solution.