You paint a picture I recognize. It sounds very similar to the United Kingdom model, with data held in multiple places, often with conflicting information.
I'm very much a believer in the citizen having access to their data and control over it precisely for that reason. I think the citizen is the ultimate arbiter of their own data, subject to some validation, obviously, where necessary, by the government. Maintaining their own records would be a good way to do it, as we do with commercial organizations when we log in and update our credit card details or our address records.
Some of the U.K. has started to do that. We now have a single tax portal. When I log in, it not only shows me my current tax position but also my state pension position, even though that data is coming from a separate department. It enables me to see in one place data that spans more than one government silo.
I don't think necessarily that enabling citizens to access and maintain their own records means you have to pull all the data into a single database. The fear is always that if it's all in one place, a potential compromise will mean that all of that citizen's data is compromised at the same time. I think there can be good justification for silos if that is done as a design intent and if the user, the citizen, can still maintain their data through a single online service, even if the data that's updated then goes back into perhaps....
I'm thinking about areas like health, where citizens are particularly sensitive about their records potentially being made available to others. I think that in some sense, just having a silo by design around health records can be a good thing, but enabling the citizen to still update the common aspects of that record, such as addresses, across multiple government agencies could still be achieved through a single portal.
To me, it comes back to the identity issue, which really does need to be cracked first. You need to know which citizen it is and then to establish that they really are the citizen who owns those different data records. Then I agree entirely that the citizen is well placed to look at the data and to either directly make amendments and corrections or to request the appropriate corrections and amendments by the owning department.