The Distributed Application Architecture (DAA)
                                    as a
         Heterogeneous Execution Environment for Enterprise Integration

                               Joseph S. Sventek
		            Hewlett-Packard Company

The DAA is designed to allow users of a computer network to access information,
applications, and services, as well as to exchange information with others,
through a single, consistent user environment.  It enables the construction of
new applications and services; it also provides facilities for the integration
and migration of existing applications.

A complete system based on the DAA includes both components which supply
services provided as part of the infrastructure and a set of conventions or
policies defining how components are to interact with the provided services and
with each other.

Since the DAA is intended to support a wide range of application areas,
features which are needed in some contexts may not be appropriate in others.
This leads to the following layered architectural model:

 * The DAA Core provides basic functionality common to all DAA systems; this
   Core is consistent with OMG/CORBA.

 * The DAA also defines policies (interfaces and protocols) and supporting
   services which are constructed over the Core.  These policies and services
   may differ among application areas.  Those defined to date include:

    + event notification
    + object relationships/links
    + object properties
    + object lifecycle
    + naming
    + protocol negotiation
    + presentation/semantic split

The DAA Core is also logically structured to permit the incorporation of
existing object technologies.  Current efforts include architectural support
for the management of ISO managed objects, as well as, communication support
for object groups.

The paper describes the basic architecture and focusses upon the policy layer
as the critical portion to achieve application integration.