I'm confused by his five example for "1.2.3. Access Path Dependence" (page.378), where an app would fail if the data representation changed, because I think an app using a relational store would also fail if the relations were organized differently. I can see some possible resolutions, but the paper doesn't address the issue...
I concede that it's hard to assess a proposed approach when it doesn't actually exist yet; but I think that if you raise an issue with the existing approaches in a paper, it's reasonable to also assess your own proposal with respect to that issue.
e.g. maybe he imagined automatic views to convert the underlying relations (so that different relations are identical if they represent the same information...); or a manual conversion layer with views (but the same could be done for the other store!); or maybe he was only thinking of different physical representations when he wrote that part and it didn't occur to him that different relations also might be used
I think he's saying that while the relational model has the same problem of retaining compatibility for old apps when it evolves, it this is * easier * to do this with the relational model. ie. the "number of access paths" for old apps becomes "excessively large" for non-relational models. He talks a bit about the complexity of representing different queries later on, but somewhat obliquely and doesn't draw the connection (and I don't quite follow what he means in the second last paragraph of section 1.5, where he mentions n!, 2n-1 and n+1 - I understand it so little, that I think there might be a typo).
I'm confused by his five example for "1.2.3. Access Path Dependence" (page.378), where an app would fail if the data representation changed, because I think an app using a relational store would also fail if the relations were organized differently. I can see some possible resolutions, but the paper doesn't address the issue...
I concede that it's hard to assess a proposed approach when it doesn't actually exist yet; but I think that if you raise an issue with the existing approaches in a paper, it's reasonable to also assess your own proposal with respect to that issue.
e.g. maybe he imagined automatic views to convert the underlying relations (so that different relations are identical if they represent the same information...); or a manual conversion layer with views (but the same could be done for the other store!); or maybe he was only thinking of different physical representations when he wrote that part and it didn't occur to him that different relations also might be used
EDIT http://www.aisintl.com/case/library/Date_Birth%20of%20the%20...
I think he's saying that while the relational model has the same problem of retaining compatibility for old apps when it evolves, it this is * easier * to do this with the relational model. ie. the "number of access paths" for old apps becomes "excessively large" for non-relational models. He talks a bit about the complexity of representing different queries later on, but somewhat obliquely and doesn't draw the connection (and I don't quite follow what he means in the second last paragraph of section 1.5, where he mentions n!, 2n-1 and n+1 - I understand it so little, that I think there might be a typo).
Ah! He seems to have addressed it more directly in a previous, less-cited IBM-only paper from 1969... to which I happen to have a link right here: http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.173.5...