Awesome Niels! maybe you could blog or document some cool example on this?
Cheers, /peter neubauer COO and Sales, Neo Technology GTalk: neubauer.peter Skype peter.neubauer Phone +46 704 106975 LinkedIn http://www.linkedin.com/in/neubauer Twitter http://twitter.com/peterneubauer http://www.neo4j.org - Your high performance graph database. http://www.tinkerpop.com - Processing for Internet-scale graphs. http://www.thoughtmade.com - Scandinavias coolest Bring-a-Thing party. On Fri, Mar 26, 2010 at 5:22 PM, Niels Hoogeveen <pd_aficion...@hotmail.com> wrote: > > Using Scala, I was actually able to extend MetaModelThing to act as a Node > and MetaModelClass to have shadowing functionality for both MetaModelClasses > and for MetaModelProperties, without touching the original source code. > >> To: user@lists.neo4j.org >> From: rick.bullo...@burningskysoftware.com >> Date: Fri, 26 Mar 2010 14:29:03 +0000 >> Subject: Re: [Neo] meta meta classes >> >> Such are the joys and challenges of frameworks and abstractions. Sometimes >> you do need to get "close to the metal" though, to achieve specific >> functional and performance requirements. Thus the reason open source >> frameworks are awesome. At least we can change and extend them more easily! >> >> >> >> -----Original Message----- >> From: Niels Hoogeveen <pd_aficion...@hotmail.com> >> Date: Fri, 26 Mar 2010 15:20:15 >> To: <user@lists.neo4j.org> >> Subject: Re: [Neo] meta meta classes >> >> >> Making MetaModelThing implement the Node interface is actually orthogonal to >> the creation of Shadow objects. Though it does make code using classes as >> objects cleaner, and allows the node property of MetaModelThing to become >> private. >> >> > From: pd_aficion...@hotmail.com >> > To: user@lists.neo4j.org >> > Date: Fri, 26 Mar 2010 14:38:08 +0100 >> > Subject: Re: [Neo] meta meta classes >> > >> > >> > Or, and this probably the simplest solution. Let a MetaModelThing >> > implement the Node interface. This allows a class to be an instance of >> > another class and/or a SubType of another class. >> > >> > >> > > From: pd_aficion...@hotmail.com >> > > To: user@lists.neo4j.org >> > > Date: Fri, 26 Mar 2010 14:20:07 +0100 >> > > Subject: Re: [Neo] meta meta classes >> > > >> > > >> > > The class as object phenomenon is actually quite pervasive, and I think >> > > it is possible to have a generalized solution for it. >> > > >> > > After sending this email yesterday, I came up with a slightly different >> > > solution. >> > > >> > > val taggable = namespace.getMetaClass("taggable", true) >> > > >> > > val tagName = metaModelNamespace.getMetaProperty("tagname", true) >> > > tagName.setCardinality(1) >> > > >> > > val metaTaggable = metaModelNamespace.getMetaClass("taggable", true) >> > > metaTaggable.getDirectProperties.add(tagName) >> > > metaTaggable.getDirectInstances.add(taggable.node) >> > > >> > > val body = namespace.getMetaClass("body", true) >> > > taggable.getDirectSubs.add(body) >> > > >> > > Instead of directly relating the class "body" to the meta class >> > > "taggable", I create a shadow of the meta class "taggable" with the same >> > > name in the namespace of the class "body", and make "body" a subclass of >> > > this shadow. That way the sub classing relationship remains nicely in >> > > one name space, while the instance relationship transcends name spaces, >> > > as it should. >> > > >> > > This could in principle be generalized by adding a methods to >> > > MetaModelClass: >> > > >> > > public MetaModelClass createShadowClass(NameSpace ns){ >> > > >> > > MetaModelClass mc = ns.getMetaClass(this.getName(), true); >> > > this.getDirectInstances.add(mc.node); >> > > return mc; >> > > } >> > > >> > > This returns a shadow of a given MetaModelClass in a given namespace and >> > > adds it as a an instance of this. >> > > >> > > It would of course be nicer to have a method with the signature: >> > > >> > > public MetaModelClass getShadow(NameSpace ns, Boolean create) >> > > >> > > This is much more in line with the rest of the API, but requires a way >> > > to find out the namespace a given MetaModelClass is defined in. I didn't >> > > see a method getNamespace() for a given class, and didn't delve deeply >> > > enough in the source code to figure out how to do that. >> > > >> > > A similar approach can of course also be applied to MetaModelProperties, >> > > by adding the following method to MetaModelClass: >> > > >> > > public MetaModelProperty >> > > createShadowProperty(NameSpace ns){ >> > > >> > > >> > > >> > > MetaModelProperty mp = >> > > ns.getMetaProperty(this.getName(), true); >> > > >> > > >> > > this.getDirectInstances.add(mp.node); >> > > >> > > return mp; >> > > >> > > } >> > > >> > > >> > > This way the underlying node of a MetaModelProperty can properly be used >> > > as a class of its own and have properties, relationships, that can be >> > > further modeled in the meta layer. This e.q. allows to set a default >> > > rendering format for a given property class. >> > > >> > > I don't see a MetaModelRelationships, which is unfortunate, since that >> > > would allow the modeling of the properties of a Relationship. >> > > >> > > >> > > Kind regards, >> > > Niels Hoogeveen >> > > >> > > >> > > > Date: Fri, 26 Mar 2010 11:26:29 +0100 >> > > > From: matt...@neotechnology.com >> > > > To: user@lists.neo4j.org >> > > > Subject: Re: [Neo] meta meta classes >> > > > >> > > > That's an interresting case you've got here and it looks to me like >> > > > it's >> > > > probably the best way to model it in the meta model. >> > > > >> > > > 2010/3/25 Niels Hoogeveen <pd_aficion...@hotmail.com> >> > > > >> > > > > >> > > > > For my application, I want to model an HTML template in Neo4J, using >> > > > > the >> > > > > MetaModel api. >> > > > > >> > > > > So I started setting up MetaModelClasses for the various HTML >> > > > > entities. >> > > > > >> > > > > e.g. (code in Scala) >> > > > > >> > > > > val classProp = namespace.getMetaProperty("class", true) >> > > > > val idProp = >> > > > > namespace.getMetaProperty("id", true) >> > > > > idProp.setCardinality(1) >> > > > > >> > > > > >> > > > > val body = namespace.getMetaClass("body", true) >> > > > > body.getDirectProperties(classProp) >> > > > > body.getDirectProperties(idProp) >> > > > > >> > > > > >> > > > > Which creates a class named "body" which has a property named "class" >> > > > > without a cardinality restriction and a property named "id" with a >> > > > > cardinality restriction of 1. >> > > > > >> > > > > Now I can create nodes of class "body" with various values for >> > > > > "class" and >> > > > > for "id". >> > > > > >> > > > > So far so good, but now I want to say that the class body has a >> > > > > property >> > > > > "tagname" which should get the value "body". >> > > > > >> > > > > The meta model itself doesn't allow classes to have properties, but >> > > > > it >> > > > > allows access to the underlying node of the class. >> > > > > >> > > > > So I created a separate namespace for the meta meta classes and >> > > > > added the >> > > > > following three definitions: >> > > > > >> > > > > val tagName = metaNamespace.getMetaProperty("tagname", true) >> > > > > tagName.setCardinality(1) >> > > > > val taggable = metaNamespace.getMetaClass("taggable", true) >> > > > > >> > > > > body.node.setProperty("tagname", "body") >> > > > > >> > > > > This creates a property "tagname" with the value "body" for the >> > > > > class named >> > > > > "body". >> > > > > >> > > > > Now comes the more ambiguous part, how to link "body" to "taggable". >> > > > > >> > > > > I can make body.node an instance of taggable. Once there is a >> > > > > validator, >> > > > > the existence of a "tagname" property with cardinality 1 should be >> > > > > checked, >> > > > > so it is reasonable to make body.node an instance of taggable. >> > > > > >> > > > > At the same time the class body is actually a subclass of taggable, >> > > > > so I am >> > > > > inclined to define that as well. >> > > > > >> > > > > So I end up doing the following: >> > > > > >> > > > > taggable.getDirectInstances.add(body.node) >> > > > > taggable.getDirectSubs.add(body) >> > > > > >> > > > > I would like to know if this is the correct approach to this >> > > > > situation, or >> > > > > whether there are better alternatives. >> > > > > >> > > > > Kind regards, >> > > > > Niels Hoogeveen >> > > > > >> > > > > >> > > > > _________________________________________________________________ >> > > > > New Windows 7: Find the right PC for you. Learn more. >> > > > > http://windows.microsoft.com/shop >> > > > > _______________________________________________ >> > > > > Neo mailing list >> > > > > User@lists.neo4j.org >> > > > > https://lists.neo4j.org/mailman/listinfo/user >> > > > > >> > > > >> > > > >> > > > >> > > > -- >> > > > Mattias Persson, [matt...@neotechnology.com] >> > > > Neo Technology, www.neotechnology.com >> > > > _______________________________________________ >> > > > Neo mailing list >> > > > User@lists.neo4j.org >> > > > https://lists.neo4j.org/mailman/listinfo/user >> > > >> > > _________________________________________________________________ >> > > Express yourself instantly with MSN Messenger! Download today it's FREE! >> > > http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ >> > > _______________________________________________ >> > > Neo mailing list >> > > User@lists.neo4j.org >> > > https://lists.neo4j.org/mailman/listinfo/user >> > >> > _________________________________________________________________ >> > New Windows 7: Find the right PC for you. Learn more. >> > http://windows.microsoft.com/shop >> > _______________________________________________ >> > Neo mailing list >> > User@lists.neo4j.org >> > https://lists.neo4j.org/mailman/listinfo/user >> >> _________________________________________________________________ >> New Windows 7: Find the right PC for you. Learn more. >> http://windows.microsoft.com/shop >> _______________________________________________ >> Neo mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user >> _______________________________________________ >> Neo mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user > > _________________________________________________________________ > New Windows 7: Find the right PC for you. Learn more. > http://windows.microsoft.com/shop > _______________________________________________ > Neo mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ Neo mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
