OpenIGTLink/Discussion/NewCommands

Common get list ?

A common GET_LIST message could be defined with the data type, like IMAGE, in the device name field. The answer could be a LIST message with ids (each 20 bytes, so it can they used as device names) of available data. Afterwards a GET_xy message with the id could be used to query the details.

Well, I don't think this will help in practice.

Example: an application would like to show a list of available images before querying them from the server. Ids are not very specific, so an additional meta data message must be defined. So we have a) GET_LIST and b) for each id: GET_IMGMETA. It would be easier to get all the meta data at once, which returns a list of meta data.

Next example: all ficucial points shall be queried. A two-step mechanism would result in 1+n queries, whereas getting all points at once would end in only 1 query. Even if the user would like to get only 1 specific point, how could he know which id to use?

Another reason is that sending all the data at once is much more efficient.

However, there might be use cases, where single items are useful. If the item size is constant, it makes no difference if only one or several items are transmitted. The number is bodySize/itemSize. Using this definion, single items can still be pushed over the network as it's currently done in most OpenIGTLink applications.

Image data

IMAGE + COLORTABLE + METADATA

Point or fiducal data

POINTS

Start / stop push

START_PUSH + STOP_PUSH

Tracking data

TRACKINGDATA