ITXA is also known as Standard Processing Engine, Documentation sections use the products name ( ITXA) as Websphere Transformation Extender.

Installation

You can install the Websphere Transformation Extender from any supported version of Linux, Unix, or windows operating system.
You can see more details about IBM ITXA

Document flow of Standard Processing Engine

It includes in 2 functions :
Envelope and de- envelope
Transforming

Document flow of De -envelope:

An X12 or EDIFACT document is passed to Standards Processing Engine. A single document often contains multiple groups, interchanges, and transactions.
Including validation, through the SPE API, WebSphere Transformation Extender SPE adapter, a Sterling B2B Integrator service for SPE, or through an IBM Integration Bus node, exposing its routing information and contents.
Based on a trading partner, standard, and transaction information, SPE selects the transformation map that is needed to process the transactions
The output API splits out multiple transactions, if necessary.
The transactions are transformed, and an acknowledgment is generated for each transaction.
All data is passed back with the response.

Envelope:

Envelopes EDI transactions. The message flow can be summarized as follows:
The SPE node accepts one or more documents from the invoking application.
It does a document translation that is based on the trading partner information.
It wraps envelope headers around the translated documents, as defined by the trading partner information.
It returns enveloped documents on response.
If deferred enveloping is being used, prepared documents are held in the database in a ready state instead of being enveloped. Documents are enveloped when that response is triggered.

Transform:
SPE receives a message from the invoking application.
Header information in the message is used to interpret the standard.
Assuming that the standard is supported, a map is called.
The document is transformed according to the instructions on the map.
During map execution, input data is validated to assure that it matches the input definition.
IBM ITXA