Expressions

In the previous sections of this guide, you have seen basic examples in which bits of text performed control or mapping of data. A DML expression is one of those bits of text. The whole purpose of an expression is to make the integration engine behave in a certain way.

Expressions are composed of statements. Expressions must follow a very precise syntax, otherwise your expressions are rejected. For example, among the primary rules of syntax is the required use of the semicolon ; to separate statements from each other.

Statements tell the integration engine server to perform some elementary tasks. Various actions can be performed in statements; the verbs that state those actions are called instructions or operators.

Instructions and operators are English words that have special meanings in DML expressions. They are the reserved keywords of the language; this means that you cannot use those words outside their specific purpose.

An example of DML in an expression is this simple mathematical computation:

(1992 + 89) * 78.9

This expression tells the integration engine to add 89 to 1992 and then to multiply the results by 78.9. The meaning is absolutely the same as in conventional math expressions. Notice the use of reserved characters (, ), + and * as arithmetical symbols for priority, addition, and multiplication.

In this example, the result value that is generated is: 164190.9. Most DML expressions generate a value that is used by the integration engine as either the result of data check, or to fill nodes of output data.

This is why expressions are bound to Business Documents or Business Document nodes. The value generated by a Validation Rule of a Business Document states whether the input document has been successfully checked or not. Values generated by Maps are used by the integration engine server to fill the corresponding nodes in the output Business Document.

Instructions and operators act on objects as shown in the numbers in the previous example. Those numbers are among the most primitive object you can see in expressions: literals. More complex objects do exist in the integration engine; these are referred to using their names.

The following is the list of DML reserved keywords and characters.

Reserved keywords and characters

(

)

{

}

[

]

;

,

+

-

/

&

:=

=

<>

\

\\

..

*

:

$

in

out

<

<=

>=

>

"

'

@

@@

%

!

{#

#}

**

and

attribute

absent

break

case

child

default

defined

do

else

exit

each

for

false

if

item

into

loop

next

not

null

on

or

parse

select

switch

tree

this

then

to

times

terminal

true

undefined

while

where

xor

 

 

 

 

 

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