HISA specifies fundamental requirements for 'information infrastructure' and healthcare specific middleware
services.
This part of the standard specifies the fundamental characteristics of the computational model to be
implemented by a specific architectural layer of the information system (i.e. the middleware) to provide a
comprehensive and integrated interface to the common enterprise information and to support the fundamental
business processes of the healthcare organisation, as defined in the document "Health Informatics - Service
Architecture - Part 1: Enterprise Viewpoint". The computational model is specified without any -explicit or
implicit- assumption about the physical technologies, tools or solutions to be adopted for its physical
implementation in the various target scenarios. The specification is nevertheless formal, complete and non-
ambiguous enough to allow implementers to derive an efficient design of the system in the specific
technological environment that will be selected for the physical implementation.
The computational model provides the basis for ensuring consistency between different engineering and
technology specifications (including programming languages and communication mechanisms) since they
must be consistent with the same computational object model. This consistency allows open inter-working and
portability of components in the resulting implementation.
This specification does not aim at representing a fixed, complete, specification of all possible interfaces that
may be necessary for any requirement of any healthcare enterprise. It specifies only a set of characteristics -
in terms of overall organisation and individual computational objects, identified as fundamental and common
to all healthcare organisations, and that are satisfied by the computational model implemented by the
middleware.
Preserving consistency with the provisions of this standard, physical implementations shall allow extensions to
the standard computational model in order to support additional and local requirements. Extensions shall
include both the definition of additional properties in the objects of the standard model and the implementation
of entirely new objects.
Also this standard specification shall be extendable over time according to the evolution of the applicable
standardisation initiatives. The specification of extensions shall be carried out according to the methodology
defined in paragraph 7 "Methodology for extensions" of document EN 12967-1 "Health Informatics - Service
Architecture - Part 1: Enterprise Viewpoint", which identifies a set of healthcare common information services,
describing their need and the methodology through which they will be used. These are only the minimal
identifiable set of services according to the needs of the healthcare enterprise, and constituting the
'middleware' platform (i.e. integration platform) to serve as the basis for healthcare applications, e.g. EHR or
patient administration.