New table constraint planned for Pandamator (Constraints on workflow paths, part 3)

Building upon the thoughts in part 1 and part 2 of this series of posts, I’m planning a new table constraint for Pandamator.

First of all, I have created Pandamator as a public project in the Flying Donut tool. So you’ll be able to keep tags on me while I’m moving Pandamator forward. Once you’re at it, you can register for free, and use it for your own projects. Don’t worry if you are not an expert Donut Flyer, a sample project will be created for you to play with upon your registration. I have great hopes for this tool and I have actually invested for its development. So I’m putting my money where my mouth is, by using it for Pandamator!

You’ll find an iteration (SCRUM terminology) for the new table constraint, there, so I’m not going to explain breakdown into items and tasks. I’m going to give you the outline of how I’m planning it to work. It’s the first big addition that diverges from ATSQL. Here’s what I’m thinking it should look like.

ALTER TABLE T ADD VALIDTIME CONSTRAINT C CHECK('[] p1 -> <> p2')
WHERE p1 = AMOUNT > 100, p2 = POSITION > 2

It’s a variation of the CHECK constraint, where the constraint is not a logical expression, but a string. This is done so that the constraint itself will be whatever SPOT accepts (LTL and PSL), without interfering with SQL grammar. The connection to SQL grammar will be in the WHERE clause that follows this novel CHECK constraint, which will provide the meaning of the propositions, inside LTL/PSL, as SQL expressions on the object in question. I settled on that as a solution to ensure separation of concerns and a smooth transition between the two domains. SPOT will do its job, and create the Büchi automaton, and Pandamator will generate proper SQL for the propositional logic formulas within, by plugging in the propositions defined in the constraint. Before that, I toyed with grandiose ideas of extending the SQL grammar to add LTL/PSL, but the solution I’m proposing here seems a lot cleaner, in the end.

I’ll post an update when this progresses a bit, and you can keep track of it yourselves at the relevant iteration.

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One thought on “New table constraint planned for Pandamator (Constraints on workflow paths, part 3)

  1. Pingback: New Table Constraint Planned for Pandamator, part 2 | dsouflis

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