Currently the read/write services access a single attribute per request. It currently supports multiple requests per message but when reading a large number of attributes from multiple nodes this gets very chatty and inefficient.

Desired feature: in a single request a client can ask for multiple attribute values and the reply contains multiple values.

Strawman proposal: Define new read service that takes an additional argument: a a 64 bit mask that specifies the attribute(s) to be returned in the reply. The bit position specifies the enumerated attribute ID, shifted left so that bit 0 corresponds to attribute ID=1, bit 1 ==> attribute ID =2 , etc.
The reply values are returned by position so that they align with the bit mask.

Use case 1:
UAExpert: each time a node is selected it sends a message requesting all the attributes of a node. Each one is a separate read command packaged within a single message.

Use case 2:
A user wants to select nodes for data acquisition in an HMI. To do this the UA client front-end must determine which nodes are suitable for data acquisition. It requests attributes DataType, Access Rights: user, role, etc., ValueRank, ArrayDimensions etc. After filtering these based on business logic it presents a summary of these nodes to a user so she can select the ones of interest.
When a Object node contains a large number of Variable nodes this will take a very long time and will result a sub-optimal user experience (i.e. user must take a coffee break before it can be used) .