Cloud ontology: to boldly go where ITIL, Grid and SOA have gone before

I wasn’t at the recent Cloud interop meeting in Mountain View, but based on blog reports from those who were (Stu, James and Bob) a key takeaway is that we need a “Cloud taxonomy”.

As John points out, there are plenty of existing proposals. The SPI taxonomy (SaaS/PaaS/IaaS), the SADIST-PIMP taxonomy (Storage, App, DB, Info, Security, Test, Platform, Integration, Management, Process - which I took the liberty to re-order) and the UCSB/IBM “Toward a Unified Ontology of Cloud Computing” paper.

Is it a matter of picking one of these? And if we do, how are we better of?

Let’s look at some related domains that are a bit more mature to see how they handled this and what benefits they got out of it. The three most relevant comparison I can come up with are ITSM, Grid Computing and SOA.

ITSM has ITIL, a key part of which is its glossary which provides value in and of itself, even if you don’t explicitly use the rest of the framework. Is this what the Cloud taxonomy should aim for? I contend that the Cloud field is not nearly mature enough to aim for this.

Grid Computing has OGSA, which started as a white paper containing a service model (section 6.1). It was later expanded (within GGF, a standards organization specific to Grid Computing) into this document and was used as a basis for many standard technical specification. Is the goal of the Cloud Ontology to follow a similar path? OGSA was more than a glossary though, it included a vision, goals and architectural recommendations. Sure you can start with the glossary, but I am willing to bet that a stand-alone glossary would change significantly if/when a Cloud Computing architecture is defined based on it. And there isn’t today, for Cloud Computing, the singularity of vision that the Globus gang brought to Grid Computing and that is necessary for an architecture.

SOA was never as structured. There was an early attempt, called the Web Services Architecture at W3C. Like OGSA, this is a high level architecture, not just a taxonomy. In any case, the WSA work didn’t really end up having much of an influence in SOA (or even Web services) practice. Then came the SOA Reference Model, an OASIS standard. Of the three (ITIL, OGSA, SOA-RM) this is what I think is closest to what a Cloud taxonomy should aim for at this point. An ITIL-like glossary would be too brittle (if it has any depth) and it’s too early for an OGSA-like architecture.

Again, I was not at the meeting and only know what was blogged about. This is not a criticism of the proposal, just some thoughts about how it might compare to similar efforts.

Side note #1: I prevented myself from going off about the difference between a controlled vocabulary, a glossary, a taxonomy and an ontology. These differences are not germane to the present discussion. And I am not wearing my pedantic hat today (for once). If some want to call a wedding cake an ontology, who am I to stop them?

Side note #2: Speaking of trying to be less pedantic in 2009, this entry represents my capitulation: I finally created a “Cloud Computing” category in this blog, rather than my prefered designation, “Utility Computing”, which I have been using so far. A small step for me, a microscopic step for humanity.

[UPDATED 2009/1/28: We're getting there (fast!). Via John, this updated taxonomy graph from Chris Hoff is going in the right direction, I think. Next step: more text describing the relationships between the boxes to have more of a model.]

From William Vambenepe's blog