Imported from previous forum
Hi,
I am attempting to add preliminary support for bit groups and noticed that within the latest version of the FAST 1.2 extension proposals, it is not specified whether or not a bit group field supports a presence attribute. Are presence attributes supported for bit groups?
Also, the bit group proposal implies that the bit group field does support (some) field operators as a copy operator is present within the syntax examples.
If field operators are supported as well as a presence attribute, it seems like a NULL representation is required for bit groups. How should NULL be represented? Also, what is the interaction of the bit group’s presence attribute and field operator, if any, with fields within the bit group?
Thanks,
Donnell Bell
According to my implementation, the bitGroup needs no presence attribute. Because unlike those of a group, the elements are grouped just for the purpose of space saving and they are unnecessarily semantically relevant.
However, you can still implement the presence of the bitGroup. That will be compatible for either situation.
BTW, the bitGroup should have a PMAP if it is a segment (although this is a different question).
To judge whether a group/bitGroup is a segment or not, the slot-needing situation of all its sub-elements should be scanned. If any of them need a slot, the bitGroup is a segment, otherwise not a one.
FYI
Guangbin Xu
Shanghai Stock Exchange
Hi,
I am attempting to add preliminary support for bit groups and noticed that within the latest version of the FAST 1.2 extension proposals, it is not specified whether or not a bit group field supports a presence attribute. Are presence attributes supported for bit groups?
Also, the bit group proposal implies that the bit group field does support (some) field operators as a copy operator is present within the syntax examples.
If field operators are supported as well as a presence attribute, it seems like a NULL representation is required for bit groups. How should NULL be represented? Also, what is the interaction of the bit group’s presence attribute and field operator, if any, with fields within the bit group?
Thanks,
Donnell Bell
Hi,
The current proposal is silent on the use of the presence attribute on individual fields in bit groups. It is also silent on the use of the presence attribute on the bit groups as a whole. These issues will be addressed in an upcoming update to the proposal. The current intention is that both the bit group itself and its individual fields will have nullable representations, that is, will allow the presence attribute in the template.
The field operator is for the bit group as whole. Field operators will not be allowed for individual bit group fields.
/David
Hi,
I am attempting to add preliminary support for bit groups and noticed that within the latest version of the FAST 1.2 extension proposals, it is not specified whether or not a bit group field supports a presence attribute. Are presence attributes supported for bit groups?
Also, the bit group proposal implies that the bit group field does support (some) field operators as a copy operator is present within the syntax examples.
If field operators are supported as well as a presence attribute, it seems like a NULL representation is required for bit groups. How should NULL be represented? Also, what is the interaction of the bit group’s presence attribute and field operator, if any, with fields within the bit group?
Thanks,
Donnell Bell