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Solving directed graph problems with SQL

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by maryweilage

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This week's Oracle e-newsletter explains how to solve directed graph problems with SQL. How often do you use directed graphs in your development work? Will this tip be useful to you in your shop? Why or why not?

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6 replies

by avia

> How often do you use directed graphs in your
> development work?

Never.

> Will this tip be useful to you in your shop?

Definitely.

> Why?

Because it has made me aware of a possible solution for a certain class of problem. If I encounter a problem that I recognize as being a directed-graph-type problem, I will check whether Scott's solution is applicable.

by xsfphhqjobkb

I intend to save this article for further examination for
representing graphs of workflow and status changes of
documents.

by swstephe

Part 2 will be coming out soon. It will use the same algorithm, but applied toward a classic "state machine" problem: generating a parser. It may be a bit closer to workflow management.

by xsfphhqjobkb

Part 2 is cool. Perhaps it could be used to drive the
controller in a Model-View-Controller implementation. If in
state i viewing page P and button for action A was pressed
then run code C, go into state j and display page Q.

by maryweilage

In part two of this series in our Oracle e-newsletter, author Scott Stephens explains how to combat a state machine problem with SQL.

Is this two-part series useful to you now, or do you think you might utilize the author's advice in future development work? Please let us know.

by swstephe

In the first article, I mentioned how SQL could take a table of "edges", (plane flights), and derive paths. In the second one, I used known paths, (words/sequences of letters), to derive a set of "edges", (transitions between letters).

A friend of mine has a startup which manages software test suites by generating every possible test case for an application, (and requiring software engineers to write and sign off every test before the software was accepted). That would probably be a good fit for MVC states, generating/examining all the possible user input transitions with the model transitions.

I've played around with the idea, but haven't had time to write it, of having a state machine editor which could generate application code for UI, webservices and back-end application ... taking advantage of topics like state-machine switches.

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