Hi Randolph, The problem with ORM systems would ultimately be a rather bloated schema and hard-wired classes to accommodate that schema. Yes and no, it depends on your configuration. One configuration could end up using only on talbe with many columns, other configurations could break up this table to normalize the schema. I don't understand the "hard-wired classes to accommodate that schema", the openEHR RM is an Object Oriented model, a programmer should implement the model on the ORM tool and the schema should be generated from those classes, in fact is the schema what accommodates to the classes. So, for new versions of the RM, a new schema could be generated, an mappings between those schemas could be generated to (for data migration, if needed). Yes, ORM lets you automate the creation of DB data structures and classes, but, once created, they become part of the schema and your DLLs, which is fine until you have many hundreds of them (tables and classes defined in autogenerated code, etc.).
Yes, you'll end up with a schema, a fixed one, that depends on the RM version you use, if the RM version change, the schema should change too, but the RM version you'll use will be very stable, nd I'm sure that only one version of the RM will be in use at a time. ORM generates the schema for the classes (source code), not the classes for the schema, so we don't have "autogenerated code". This is my experience and the way I think this should be done, because the openEHR Reference Model is Object Oriented, so a programmer could easily program those classes and user an ORM tool to generate the database structure. DLLs? Kind regards,Pablo. Randy Neall Veriquant, L.L.C. On Thu, Feb 16, 2012 at 5:26 PM, pablo pazos <pazospablo at hotmail.com> wrote: Hi M?rcio, There is no standard persistence model, the persistence mechanism is not in the standard scope. There are many ways of storing openEHR RM instances (archetyped data), the only thing to take into account is that the information to store will be highly hierarchical. Said that, in EHRGen [1] we use a relational model with an Object-Relational Mapping [2] tool (GORM from Grails Framework[3]). The advantage of that is that you have a complete and validated RM instance persisted on the DB, and you can query for complete objects or single data ELEMENTS. I've written ORM tools myself [4] and the main problem is the amount of joins you need to load a complete structure, but in my experience you never load a complete structure for a real time interaction with the user, and you alway can cach? some data. This approach is straight forward, because all you need are the classes of the RM, and you delegate DB stuff to the ORM tool. Other models are viable too, like K/V [5] or EAV [6] approaches (mentioned by Bert). This approaches are fast for saving and loading data, the problem is that you need to have some complex logic above that for constructing a complete RM instance on memory, because K/V is a flat representation of a higly hierarchical tree structure. Other models I didn't try yet are Object Oriented DBs and Document Oriented DBs (XML, JSON, ...) [6]. I think DODBs are a good option, fast for store highly hierarchical structures, but you need to write some ugly queries if you want your data back :D Hope that helps. [1] http://code.google.com/p/open-ehr-gen-framework/ [2] http://grails.org/ [3] http://en.wikipedia.org/wiki/Object-relational_mapping [4] http://code.google.com/p/yupp/ [5] http://en.wikipedia.org/wiki/NoSQL [6] http://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model -- Kind regards, Ing. Pablo Pazos Guti?rrez LinkedIn: http://uy.linkedin.com/in/pablopazosgutierrez Blog: http://informatica-medica.blogspot.com/ Twitter: http://twitter.com/ppazos From: [email protected] Date: Thu, 16 Feb 2012 16:53:19 -0300 Subject: openEHR - Persistence of Data To: openehr-technical at openehr.org Hello guys, i'm starting a research about the persistence model of Archetype data, that stores the information entered by the user of the system. I would like to know if there is a indication of the openEHR standard for what kind of model schema should be used in DataBase, and if there are researchs in this area. Thanks in advance, M?rcio Costa B.Sc. in Computer Science @ Cin/UFPE M.Sc. Candidate in Computer Science @ CIn/UFPE MSN: mdckoury at gmail.com _______________________________________________ openEHR-technical mailing list openEHR-technical at openehr.org http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical _______________________________________________ openEHR-technical mailing list openEHR-technical at openehr.org http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical _______________________________________________ openEHR-technical mailing list openEHR-technical at openehr.org http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20120217/68f5d9e3/attachment.html>
