Would making the underlying Node publically available (via a getter) be virtually the same thing? In that case the meta model classes could have such a getter.
2010/3/26 Niels Hoogeveen <pd_aficion...@hotmail.com> > > Hi Peter, > > I added a Wiki entry in my github repo called "Reification of meta classes > and meta properties": > > > http://wiki.github.com/NielsHoogeveen/Scala-Neo4j-utils/reification-of-meta-classes-and-meta-properties > > The source code for the Scala wrappers can be found found in my repo: > > http://github.com/NielsHoogeveen/Scala-Neo4j-utils > > Kind regards, > Niels Hoogeveen > > > From: neubauer.pe...@gmail.com > > Date: Fri, 26 Mar 2010 17:25:01 +0100 > > To: user@lists.neo4j.org > > Subject: Re: [Neo] meta meta classes > > > > 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 > > _________________________________________________________________ > 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 > -- Mattias Persson, [matt...@neotechnology.com] Neo Technology, www.neotechnology.com _______________________________________________ Neo mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
