OpenNebula

I would like the option to filter the API output server-side - often, I'm finding myself in need of just a few fields of all the data stored about a VM, and this is very inefficient at large numbers of VMs, if basically all I want is a list of just two or three columns of data.

To keep backwards compatibility, I would recommend to add an option to the listing queries to specify a list of columns I want to receive. Either use a single-value with a field separator, or use multiple fields, e.g.

a)
<includeColumns>vmId|assignedIp</includeColumns>

b)
<includeColumn>vmId</includeColumn>
<includeColumn>assignedIp</includeColumn>
[...]

this will make scaling a lot simpler for large installations.