> That's interesting. What does this structure mean actually? How are you
>expected to parse it?
>
>You can always use something like IMPLICIT SEQUENCE OF ANY, and then
>read the raw der data from there and parse it as Data. However, that
>structure definition looks like a test for a parser rather than a useful
>structure.
>
>
>regards,
>Nikos
>
>
Actually MMS is the protocol which suggests an infrastructure to applied
protocols through accessing to variables. Variable object model defined as
UNNAMED-VARIABLE ::= CLASS {
&address Address,
&accessControl Identifier,
&typeDescription TypeDescription,
&value Data,
&accessMethod ENUMERATED {
public
}
}
Here Data is a variable data value and is returned as a part of AccessResult
structure of accessing to a MMS variable object.
The whole Data's structure is
Data ::= CHOICE {
-- context tag 0 is reserved for AccessResult
array [1] IMPLICIT SEQUENCE OF Data,
structure [2] IMPLICIT SEQUENCE OF Data,
boolean [3] IMPLICIT BOOLEAN,
bit-string [4] IMPLICIT BIT STRING,
integer [5] IMPLICIT INTEGER,
unsigned [6] IMPLICIT INTEGER, -- shall not be negative
floating-point [7] IMPLICIT FloatingPoint,
-- [8] is reserved
octet-string [9] IMPLICIT OCTET STRING,
visible-string [10] IMPLICIT VisibleString,
generalized-time [11] IMPLICIT GeneralizedTime,
binary-time [12] IMPLICIT TimeOfDay,
bcd [13] IMPLICIT INTEGER, -- shall not be negative
booleanArray [14] IMPLICIT BIT STRING,
objId [15] IMPLICIT OBJECT IDENTIFIER,
mMSString [16] IMPLICIT MMSString
}
MMS variable object's value could be not just a simple value but a tree-like
structure of values like this
Report (which is Data.array)
ReferenceNumber (which is Data.integer)
Name (which is Data.mMSString)
NumberOfFloatingPoint1 (which is Data.unsigned)
ListOfFloatingPointValues (which is Data.array)
Matrix_Id
FloatArray_XX (which is Data.array)
Value1(which is Data.floating-point), Value2, Value3, Value4,...
IEC60870-6-503's Bilateral Table object, Transfer Set objects and other are
mapped to MMS Named variables objects. Therefore their access results such
complex data value structures generating.
I suppose when a structure is been created asn1_create_element() shouldn't go
futher in depth than member which actually represents CHOICE. I think of CHOICE
member is something like subtree's connection point. If I wish to construct
leaf which actually tree I call asn1_write_value() with another value been
created by asn1_create_element() call.
Regards, Yaroslav.
