I find this subject very interesting and at least i didn't find any concrete definitions around these two different roles in IT, what are the main differences (in term of responsibility) between two practices/roles. I think TOGAF and Zackman architectural framework provide in detailed explanation about roles and responsibility for each role in and enterprise. I would like to share what i have got so far....
So what exactly is an Enterprise Architect vs a Solution Architect?
A Solution Architect may have a number of different types of architects working for him/her to help accomplish their task for delivering a high quality solution. For example, s/he might have an Infrastructure Architect to manage the architecture of the solution's hardware configuration so that the solution meets the Quality of Service business and IT requirements while at the same time represents the optimum way to deploy the solution into the target production environments.
There also might be a need for 'specialist' architects depending on the complexities of the business requirements or the target production environment. Such 'specialist' architects usually are called Domain Architects and examples include; Security Architect, Technology Architect (ie architects that specialize in a specific product or technology), Vertical Architects (ie architects that specialize in systems that are specialized in particular industry verticals such as Financial Services Industry, Telecommunicaitons, Public Sector, etc).
An Enterprise Architect may have also have a number of different types of architects in order to piece together a coherent, actionable future state architecture which can easily map to business strategy, be consumed by project teams and be a major contribution in governance activities.
For example, an Enterprise Architect may have Business Architects which document Business Strategies, Business Capabilities, Business Processes and Roles as well as a number of other artifacts.
Lastly, an Enterprise Architect may also have Solution Architects (aka Enterprise Solution Architects and Enterprise Application Architects) who focus on pulling all of the other Enterprise Architecture information together to shape the future state application system architecture.
Here is one place where I think there is confusion by many. You see, I described a Solution Architect at the project-level and an Enterprise Solution Architect across the enterprise and both share the words 'Solution Architect' in their role. They have VERY different purposes but are very complimentary. Could it be that simple of a reason why confustion exists? It just might be.
An Enterprise Solution Architect and project Solution Architect roles are very complimentary and because this relationship is of particular interest to me I'd like to take a moment and propose how they are to work together.
I think that the Enterprise Solution Architect be involved at the earliest point a new business initiative is created and do very high-level 'solutioning' via whiteboard and reference to future state architecture elements. Then, when the business initiative gains momentum is backed by Enterprise Architecture future state analysis the core project team is formed and the project Solution Architect takes over to be responsible for the solution. The Enterprise Solution Architect becomes a member of the project Solution Architects team and is responsible for the system integration architecture where the solution requires integration between enterprise systems as well as be responsible to provide future state system architecture guidance to help the project Solution Architect make decisions on which systems to commit to using in the solution. The Enterprise Solution Architect then is involved in governance boards to inform decision-makers with future-state architecture artifacts to help justify major technology, system, or business value decisions. Thats it.
As a quick summary, project Solution Architects and Enterprise Architects are different in that they have very different purposes. They are highly complimentary in that Solution Architects focus on delivery of solutions and Enterprise Architects focus on supporting them by documenting future state, participating on their teams and being involved in governance activities.