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Exploring Service Model Architecture
Irena Bojanova
MAY 10, 2013 09:34 AM
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painting of cowboy wrangling wild horses

It's the High-Tech Wild, Wild West out there!
Although the Cloud Computing marketplace is still chaotic, it is:

  • Exciting
  • Fast-growing
  • Full of opportunities

NIST lists three cloud service models: Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS) (please see the "As discussed in the Defining Cloud Computing" post and Figure 1).

Figure 1

Figure 1. The Cloud Model — Emphasis on Service Models.

The service model architecture defines the boundaries of the Cloud service models, how and where particular services fit, and how the discrete service models align and interact. The CSA Cloud Reference Model and some *aaS (or SPI) examples are provided in Figure 2.

Figure 2

Figure 2. Service Model Architecture.

Each *aaS model is a self-contained solution stack of integrated functionality, where IaaS provides the foundation and the other two — PaaS and SaaS — in turn build upon IaaS. A concise description of the entire stack of SaaS over PaaS over IaaS service models over the cloud infrastructure is provided in the Table 1.

Table 1. Cloud Service Models.

Service Model Description Inherited Capabilities Delivered Resources No Need to Buy/Manage
  • Foundation of all cloud services
  • Includes the entire infrastructure resource stack — facilities to hardware platforms
  • Incorporates capability to abstract resources and deliver physical/ logical connectivity to them
  • Provides set of APIs for management and other forms of interaction with the infrastructure
From Cloud Infrastructure
  • Computer infrastructure (platform virtualization environment)
  • Raw storage
  • Networking
  • Servers & software
  • Data-center space
  • Network equipment
  • +Heating/cooling
  • Sits atop/ builds upon IaaS
  • Adds layer of integration with application development frameworks, middleware capabilities, and functions (database, messaging, and queuing)
  • Allows building applications on the platform with supported programming languages and tools
From IaaS
  • Computing platform
  • Solution stack
  • Hardware
  • Software
  • Provisioning hosting capabilities
  • Builds upon IaaS and PaaS
  • Provides self-contained operating environment
  • Delivers entire user experience — content and its presentation, applications, and management capabilities
From IaaS and PaaS
  • Software on-demand — through thin clients, using web browser
  • Software
  • Data storage

Note: CSA points out also that:

  • Just as capabilities are inherited, so are information security issues and risks.
  • Commercial cloud providers may not neatly fit into the layered service models.

Cloud service model architectures may be comprised by any logical combination of the three *aaS service models over the cloud infrastructure (please see Figire 3). For example, a SaaS service model could stack directly over the cloud infrastructure, or a PaaS service model could stack over IaaS over the cloud infrastructure.

Figure 3

Figure 3. Variations of SaaS, PaaS, and IaaS Architectures.

Anyone have thoughts or sources that will help readers understand service model architecture? Please share here!

Post Note: Figure 3. should include also SaaS over IaaS over Cloud Infrastructure. Thanks to Gino Bougaardt for noticing that is missing.

Irena Bojanova

Irena Bojanova, Ph.D., is Founder of IEEE CS Cloud Computing STC, an Associate editor of IEEE Transactions on Cloud Computing, and an Editorial Board Member of IEEE CS IT Professional. She is a professor and program director, Information and Technology Systems, at University of Maryland University College, managed academic programs at Johns Hopkins University and PIsoft Ltd., and co-started OBS Ltd., (now CSC Bulgaria). Her current research interests include cloud computing, web-based systems, and educational innovations. She is a member of the IEEE and can be reached at


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