This blog is the second in a series around the usage of the CORA model in a SAP-centric environment. In the The COmmon Reference Architecture (CORA), Part I blog post, the CORA model has been introduced. In this second blog post, the SAP SOA Reference Architecture is mapped onto the CORA model.
Architectural views of SAP and CORA scope
The SOA Reference Architecture of SAP describes a SOA-based layered architecture.
This Reference Architecture describes a SOA-based layered technology. Service-enabled applications contain required functionality. The provisioning layer provides abstraction from the actual backend systems by providing a consistent set of services. SOA middleware supports service-enabling legacy systems handling the system-centric and cross-organizational processes. In the consumption layer services are utilized to create user interfaces and processes. The user interfaces layer offers several possibilities to implement user interaction based on available services.
Assessing the results
SAP is mixing Channels and Presentation technologies compared to the CORA. It mentions Portal but also Adobe Form which in itself can be accessed throughout a Portal as an electronic form. Back-end connectivity and Service Bus are two layers. In the CORA this is one layer but separated in different elements. The Enterprise SOA consumption layer contains the same elements as the Composition layer in the CORA. The difference in the naming of the layer is interesting because composite services are not only consuming but actively providing themselves too! A Data layer is not recognized as a separate layer but positioned within applications.
SOA management is a horizontal layer while in the CORA it is positioned as a vertical layer to manage SOA on more horizontal layers. Important is the absence of a Security and IT Governance. Impact for implementing SAP is that firstly security needs to be included over all layers. Secondly the governance of SAP components and integration in the whole governance cycle including run-time governance needs to assessed.
What is the added value of CORA in the SAP field
As shown the CORA model is used as a quality instrument to assess the the SOA Reference Architecture of SAP. The following questions could be raised:
- Why are the vertical CORA layers absent?
- What are the cluster and separation criteria based upon?
- If other architecture styles than Service Oriented Architecture (i.e. N-Tier or Resource Oriented Architecture ) is used, does this reference architecture still apply?
For both an Enterprise Architecture and Software Architecture on Enterprise Level it is not possible to use solely the SOA Reference Architecture of SAP as a quality instrument because:
- within a common IT Landscape multiple architecture styles (N-tier, Service Oriented Architecture, Resouce Orientented Architecture) co-exist instead of just one,
- the clustering is based on SAP components, which can differ from other vendors.
As shown in this assesment at the (SAP) project implementation level the SOA Reference Architecture can be used to create a Solution Architecture, because of its direct relation with the SAP components. However this should only be done when it is connected to the CORA, to guarantee architectural governance between the Enterprise and the project Solution Architecture.
CORA can also be used to asses the ‘SAP Business Suite’, regarding separation of responsibilities, decoupling, re-usability, portability and substitutability of elements, by plotting the different SAP-components onto the CORA layers and elements. This will be described in the next blog.