3 ms·

I used to work at an OTA (online travel agency, ie Booking.com, Hotels.com). There's all kinds of complications to what seems to be a pretty simple thing: a bui

I used to work at an OTA (online travel agency, ie Booking.com, Hotels.com). There's all kinds of complications to what seems to be a pretty simple thing: a building with rooms that are either occupied or not. There's multiple rates per room for a single night, then there's something called room rate plans which I won't get into. In other words: it's more complicated that we think (or than it needs to be).

segmondy 8y ago
This type of things is based solved with Prolog. The issue is that folks are trying to solve declarative problems using procedural/object oriented/functional programming. Because we store data in databases, we have twisted it into a database problem but it's not. book(Room, Rate):- availableBuildings(Buildings), availableRooms(Buildings, Rooms), rate_less_than(Rate, Rooms) cheapest(Rooms, Room). However complex you think this problem is, it's pretty simple. It's a very old problem, scheduling, well understood and solved. Using the wrong tool makes it a nightmare. Using the right tool makes it ridiculously easy. The solution is not the database, but the language.
- mfrager 8y ago
  Very interesting... my inclination is that you’re probably right. Any tips on how to learn to use Prolog with pulling data from external sources?
  - segmondy 8y ago
    Prolog's DB is just a text file. You can construct a DB file by using SQL to select into a text file. You can use ODBC http://www.swi-prolog.org/pldoc/doc_for?object=section(%27packages/odbc.html%27) http://www.swi-prolog.org/pldoc/doc_for?object=section(%27pa... You can use CSV http://www.swi-prolog.org/pldoc/man?section=csv http://www.swi-prolog.org/pldoc/man?section=csv I've used the above methods. For RDF, you can load with various methods even over http http://www.swi-prolog.org/pldoc/man?section=rdflib http://www.swi-prolog.org/pldoc/man?section=rdflib
    - e12e 8y ago
      I too would like to hear about getting facts from an sql db, and writing back results from prolog - it's hard to see how a prolog text file can/could be used as a source for transactional problems like booking (making sure the answer you find can be committed while still valid). I suppose one could have a prolog service that came up with suggestions, ordered by preference, and then attempt committing them in order to the actual transactional storage layer. But I don't see how you could avoid re-implementing transactions. With an rdms you could look for options, and attempt a booking in a transaction, and have a fairly established way to resolve conflicts.

segmondy 8y ago

This type of things is based solved with Prolog. The issue is that folks are trying to solve declarative problems using procedural/object oriented/functional programming. Because we store data in databases, we have twisted it into a database problem but it's not. book(Room, Rate):- availableBuildings(Buildings), availableRooms(Buildings, Rooms), rate_less_than(Rate, Rooms) cheapest(Rooms, Room). However complex you think this problem is, it's pretty simple. It's a very old problem, scheduling, well understood and solved. Using the wrong tool makes it a nightmare. Using the right tool makes it ridiculously easy. The solution is not the database, but the language.

mfrager 8y ago
Very interesting... my inclination is that you’re probably right. Any tips on how to learn to use Prolog with pulling data from external sources?
- segmondy 8y ago
  Prolog's DB is just a text file. You can construct a DB file by using SQL to select into a text file. You can use ODBC http://www.swi-prolog.org/pldoc/doc_for?object=section(%27packages/odbc.html%27) http://www.swi-prolog.org/pldoc/doc_for?object=section(%27pa... You can use CSV http://www.swi-prolog.org/pldoc/man?section=csv http://www.swi-prolog.org/pldoc/man?section=csv I've used the above methods. For RDF, you can load with various methods even over http http://www.swi-prolog.org/pldoc/man?section=rdflib http://www.swi-prolog.org/pldoc/man?section=rdflib
  - e12e 8y ago
    I too would like to hear about getting facts from an sql db, and writing back results from prolog - it's hard to see how a prolog text file can/could be used as a source for transactional problems like booking (making sure the answer you find can be committed while still valid). I suppose one could have a prolog service that came up with suggestions, ordered by preference, and then attempt committing them in order to the actual transactional storage layer. But I don't see how you could avoid re-implementing transactions. With an rdms you could look for options, and attempt a booking in a transaction, and have a fairly established way to resolve conflicts.