Question: why the soap header must be the first child element of the Envelope element

[Yang Jiao]

In the SOAP specs, it says, "The SOAP Header is encoded as the first immediate child element of the SOAP envelope. "

Why the header must be the first child?

Is it because of SAX parser? So that the header can be processed before body?

Any other concerns?

[Ulf Dittmer]

I would guess performance reasons. The body can be quite large, and if an intermediary only needs to process the header, then this convention ensures that it doesn't need to parse the whole request.