Ok, makes sense.
It just hard to see what is new in that package and what is just "hiding" the
original API.
Probably I don't know enough about type/class system to understand the
implication of having properties and relationships on top of property-names,
properties, relationships, relationship-types and nodes.
Wouldn't it be much simpler to say, there is just one thing (Element) and this
Element can be connected to other things ?
So make no distinction between connections to other "nodes" or connection to
properties ?
then you wouldn't need all the existing API at all.
I would also leave off all the management stuff here (.e.g shutdown
add/removeXXXHandler, etc).
For interaction with the old API I would have a methods on Element (or a
Factory / Converter)
Element.from(Node)
Element.from(Relationship)
Element.from(RelationshipType)
Element.from(PropertyContainer, propertyName)
Element.from(PropertyContainer, propertyName, type)
But these interconnected elements are imho a really different approach to the
current API, so mixing things just makes it confusing. Especially keeping the
old names around when the things are actually unified carries too much "wrong"
semantics.
Michael
Am 23.07.2011 um 22:02 schrieb Niels Hoogeveen:
>
> I had to wrap many of the classes, because of the return types of several
> methods. org.neo4j.collections.graphdb.Node does not extend
> org.neo4j.graphdb.Node, even though all methods of org.neo4j.graphdb.Node are
> also defined in org.neo4j.collections.graphdb.Node.
> I realize this makes the design more brittle (then again, major API changes
> to Neo4j core need to be reflected anyway), but it does allow the API to be a
> drop-in replacement of the old API.
> I like your suggestions, and would like to incorporate those to make the API
> more fluent.
> My first goal was to create a drop-in replacement API with extended features.
> PropertyType was the result of work I did on IndexedRelationships, where I
> wanted a simple interface for the indexing of relationships based on a
> property on the end node of the relationship. For that I needed a
> "comparator" which compared a property value to some supplied value. To hide
> the details of such "comparators", I created PropertyType.
> One of the goals of the enhanced API is to allow every item in the database
> (node, relationship, relationshiptype, relationship, property name, property
> value) to be treated as if it were like a Node. So every item implements the
> NodeLike interface, allowing for the maintenance of properties and
> relationships on those items.
> This serves several purposes. First of all for the types: RelationshipType
> and PropertyType, we now have the hooks for users to implement a type/class
> system on top of Neo4J. It also allows for relationships on relationships
> (needed to create n-ary relationships), and allows for relationships and
> properties on property values, without having to resort to a bipartite graph
> layout.
> Like I stated in an earlier message, the code is a first edit and still needs
> to be thoroughly tested and documented. I posted it on Github for two
> reasons: safety and to gather feedback about the design.
> Niels
>
>> From: michael.hun...@neotechnology.com
>> Date: Sat, 23 Jul 2011 21:26:53 +0200
>> To: user@lists.neo4j.org
>> Subject: Re: [Neo4j] Hyperedges and Objects
>>
>> I don't understand why you wrapped _all_ the classes, this will make this
>> package very brittle as it has to copy all API changes?
>>
>> I rather thought of a better / fluent / more usable API on top of the
>> existing one.
>>
>> something like
>>
>> new Graph(gbd).autoIndex("name")
>> .node("name","Niels")
>>
>> .relateTo("works_on","repo","graph_collections","language","Java").index("repo","language")
>> .node("name","Someone",
>> "age",20,"gender",Gender.MALE,"birthday",sdf.parse("01.01.1970"));
>>
>> int node.getProperty("age", int.class);
>>
>> etc.
>>
>> Just convenience for users.
>>
>> And I don't really understand what property-type is for. I thought you were
>> only working on n-ary relationships?
>>
>> Btw. you can replace those unholy if clauses with polymorphism in the enum.
>>
>> Are there some tests and/or examples that uses this API ?
>>
>> Cheers
>>
>> Michael
>>
>> Am 23.07.2011 um 21:02 schrieb Niels Hoogeveen:
>>
>>>
>>> Traverser and Index are wrapped too now, so the entire API as can be
>>> accessed from GraphDatabaseService is now available in enhanced API
>>> version.
>>> The API is a drop-in replacement, all that needs to be done to make an
>>> application work against the enhanced API, is to change imports.
>>>
>>> From: pd_aficion...@hotmail.com
>>> To: user@lists.neo4j.org
>>> Subject: RE: [Neo4j] Hyperedges and Objects
>>> Date: Fri, 22 Jul 2011 04:00:18 +0200
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> I uploaded the first edit (still needs to completely be tested -
>>> IS-PRE-ALPHA quality) of the enhanced API.
>>>
>>> See:
>>> https://github.com/peterneubauer/graph-collections/tree/master/src/main/java/org/neo4j/collections/graphdb
>>>
>>> The enhanced API has several new features:
>>>
>>>
>>> 1.) A new interface RelationshipContainer, supporting createRelation,
>>> getRelation, and hasRelation methods.
>>>
>>>
>>> 2.) Relationship implements RelationshipContainer so relationships to and
>>> from relationships can be created.
>>> A relationship property is maintained containing the node ID of an
>>> associated node. This node is lazily created (and with that the
>>> relationship property is set).
>>> Relationships are stored on the associated node, while properties are
>>> stored on the relationship itself.
>>>
>>>
>>> 3.) EnhancedRelationshipType implements RelationshipContainer (and with
>>> that PropertyContainer) so RelationshipTypes can have properties and
>>> relationships.
>>>
>>> A node associated with a RelationshipType is created lazily. From the
>>> reference node a RELTYPE_SUBREF relation points to a node, containing
>>> properties corresponding to RelationshipType names. The value of this
>>> property is the node ID of the RelationshipType associated node.
>>>
>>> All relationships creation to and from a EnhancedRelationshipType and all
>>> properties setting on a EnhancedRelationshipType are performed on the
>>> associated node.
>>> All retrievals are done from the associated node.
>>>
>>> The associated node is created the first time it is needed.
>>>
>>> 4.) PropertyType implements RelationshipContainer (and with that
>>> PropertyContainer). PropertyTypes can be used in getProperty, setProperty
>>> and hasProperty style operations.
>>>
>>> PropertyTypes are parameterized with the datatype of the property. This
>>> makes it possible to support methods such as: <T>
>>> getPropertyValue(PropertyType)
>>> and setProperty(PropertyType<T>, T) that guard property values added
>>> conform to the datatype presumed by the PropertyType and property values
>>> are returned typed.
>>>
>>> A node associated with a PropertyType is created lazily. From the reference
>>> node a PROPTYPE_SUBREF relation points to a node, which points to nodes per
>>> datatype.
>>> These datatype related nodes contain properties corresponding to
>>> PropertyType names.
>>>
>>> All relationships creation to and from a PropertyType and all properties
>>> setting on a PropertyType are performed on the associated node. All
>>> retrievals are done from the associated node.
>>>
>>> The associated node is created the first time it is needed.
>>>
>>> 5.) GraphDatabaseService allows for the lookup of PropertyTypes and
>>> RelationshipTypes and enhanced Nodes and Relationships.
>>>
>>>
>>> 6.) Property implements RelationshipContainer (and with that
>>> PropertyContainer). //TODO
>>> A node associated to a property is created lazily, allowing properties to
>>> have relationships and properties.
>>> The associated node is created the first time it is needed.
>>>
>>> With these enhancements, all elements of Neo4j (Node, Relationship,
>>> RelationshipType, property name and property value) are unified, sharing a
>>> common interface RelationshipContainer (and with that PropertyContainer).
>>> Node and Relationship also extend their original interfaces, so the API is
>>> a drop-in replacement for the original API.
>>>
>>> Both ProperyType and RelatioshipType now provide the necessary methods to
>>> implement a type/class system on top of Neo4j, but nothing imposes a
>>> type/class system.
>>>
>>> Being able to create Relationships to and from Relationships opens the way
>>> to a transparent implementation of n-ary relationships.
>>>
>>>
>>> This is all neat, I believe, but I would be really happy if there could be
>>> some support in core to hide the implementation a bit more.
>>>
>>> Now:
>>>
>>> 1.) Relationships can have a property containing the node ID of the
>>> associated node. This polutes the namespace, so it would be better if there
>>> were a setLong and getLong method on Relationship, where the node ID can be
>>> stored, keeping the property name away from the property namespace.
>>>
>>> 2.) Named persistent maps from String to PropertyContainer. This would
>>> eliminate the REL_SUBREF related node and the PROP_SUBREF related nodes. It
>>> would be nice if these enhancements didn't polute the node space. Named
>>> persistent maps from String to PropetyContainer would also be helpful for
>>> fast lookup of uris and generally for the creation of unique keys.
>>>
>>> Niels
>>>> Date: Thu, 21 Jul 2011 20:38:15 +0200
>>>> From: matt...@neotechnology.com
>>>> To: user@lists.neo4j.org
>>>> Subject: Re: [Neo4j] Hyperedges and Objects
>>>>
>>>> Niels,
>>>>
>>>> sounds like fun. Looking forward to get a look at this
>>>>
>>>> 2011/7/21 Niels Hoogeveen <pd_aficion...@hotmail.com>
>>>>
>>>>>
>>>>> i made a start on this. It's not all too difficult to enhance
>>>>> relationships
>>>>> such that relationships can be created upon them, which is a first step
>>>>> towards supporting hypergraphs. In fact hypergraphs are more constrained
>>>>> than an enhanced graph that supports the creation of relationships on
>>>>> relationships.
>>>>> As it stands now, the enhanced graph can work as a drop-in replacement of
>>>>> the standard neo4j API and has enhanced methods that mirror the standard
>>>>> methods.
>>>>> I also added support for typed properties, such that methods like <T>
>>>>> getPropertyValue<PropertyType<T>> are possible where <T> is one of the
>>>>> data
>>>>> types supported by PropertyContainer.
>>>>> I will upload this within the next few days.
>>>>> Niels
>>>>>
>>>>>
>>>>> From: pd_aficion...@hotmail.com
>>>>> To: user@lists.neo4j.org
>>>>> Subject: RE: [Neo4j] Hyperedges and Objects
>>>>> Date: Mon, 18 Jul 2011 17:59:08 +0200
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> I think a hypergraph would be an interesting collection to support in
>>>>> neo-graph-collections. If I find the time, I will make a start with it
>>>>> this
>>>>> week, unless there are of course other volunteers :wink: willing to do the
>>>>> lifting here.
>>>>> Niels
>>>>>
>>>>>> From: michael.hun...@neotechnology.com
>>>>>> Date: Sat, 16 Jul 2011 23:37:48 +0200
>>>>>> To: user@lists.neo4j.org
>>>>>> Subject: Re: [Neo4j] Hyperedges and Objects
>>>>>>
>>>>>> I completely agree,
>>>>>>
>>>>>> hyperedges and the accompanying traversers should be handled in a
>>>>> library. As you probably know the traversal framework currently also uses
>>>>> the core API under the hood to perform the traversals (and no black magic
>>>>> (yet)).
>>>>>>
>>>>>> So it should be fairly easy to take that approach/code and create a
>>>>> library that abstracts the hyper-edge issues (creation, deletion,
>>>>> traversal). The position semantics based approach sounds interesting.
>>>>>>
>>>>>> Would love to see that as community contribution.
>>>>>>
>>>>>> Cheers
>>>>>>
>>>>>> Michael
>>>>>>
>>>>>> Am 16.07.2011 um 23:08 schrieb Niels Hoogeveen:
>>>>>>
>>>>>>>
>>>>>>> The question is how much easier a traverser can become when there were
>>>>> dedicated hyper edges. In a binary relation it is fairly easy to define
>>>>> one
>>>>> end of the relation as the source and the other as the target (start and
>>>>> end
>>>>> node),
>>>>>>> but in n-ary relationships the roles of the attached nodes become more
>>>>> complicated.
>>>>>>>
>>>>>>> Suppose we have the GIVES relationship, where one attached node takes
>>>>> the role of subject (the giver),
>>>>>>> one node takes the role of direct object (the gift), and another node
>>>>> takes the role of indirect object (the recipient).
>>>>>>> To traverse such a graph, we need to know these different roles,
>>>>> otherwise we may end up traversing the wrong nodes.
>>>>>>>
>>>>>>> Suppose we the following statements:
>>>>>>>
>>>>>>> John gives Paul a servant.
>>>>>>> Paul visited Albania.
>>>>>>> Paul's servant visited Albania.
>>>>>>>
>>>>>>> We now want to know all people that received a gift from John and who
>>>>> visited Albania.
>>>>>>>
>>>>>>> Without properly denoting the roles in the ternary relationship stated
>>>>> by "John gives Paul a servant",
>>>>>>> the answer to the query may well be: Paul and Paul's servant.
>>>>>>> Both are persons, both have visited Albania and both are part of the
>>>>> GIVES relationship defined.
>>>>>>>
>>>>>>> When we have to define the exact roles of each part of an n-ary
>>>>> relationship for each traversal,
>>>>>>> it is just as complicated as defining a traversal based on binary
>>>>> relationships,
>>>>>>> where different relationship types denote the roles of each part of the
>>>>> n-ary relationship.
>>>>>>>
>>>>>>> If hyperedges were to be introduced, either as a library or in core,
>>>>>>> the entire notion of the graph and how traversals are performed need to
>>>>> be rethought.
>>>>>>>
>>>>>>> The concept of an edge as having a start and an end node doesn't
>>>>> translate well into the world of hyper edges.
>>>>>>> There is not necessarily a start node and an end node,
>>>>>>> instead there are various nodes that are distinctly attached to the
>>>>> hyper edge.
>>>>>>>
>>>>>>> One way to think about an edge in both the graph and in the hypergraph
>>>>> world is as a tuple.
>>>>>>>
>>>>>>> A binary relationship can be thought of as the tuple:
>>>>>>>
>>>>>>> (node1, node2, RelationshipType, Set(property))
>>>>>>>
>>>>>>> A ternary relationship can be thought of as the tuple:
>>>>>>>
>>>>>>> (node1, node2, node3, RelationshipType, Set(property))
>>>>>>>
>>>>>>> etc...
>>>>>>>
>>>>>>> Instead of marking a binary relationship as outgoing or incoming, we
>>>>> can use the position in the tuple to denote its role.
>>>>>>> We can say the first node in the tuple corresponds to the start node,
>>>>> and the second node in the tuple corresponds to the end node.
>>>>>>> Having two possible permutations relates to the two possible directions
>>>>> an edge can have.
>>>>>>>
>>>>>>> Position based definitions of relationships translate well into the
>>>>> domain of n-ary relationships,
>>>>>>> though the semantics of such relationships can easily become difficult.
>>>>>>> A ternary relationship already has 6 permutations for the attached
>>>>> nodes,
>>>>>>> while a 10-ary relationship has 3,628,800 possible permutations.
>>>>>>>
>>>>>>> It would be an interesting project to design a tuple-position-based
>>>>> traverser.
>>>>>>> For binary relationships it should have the exact same features as the
>>>>> current direction based traverser,
>>>>>>> but it would be possible to generalize that design to n-ary
>>>>> relationships.
>>>>>>> This can all be done as a libary.
>>>>>>>
>>>>>>> Only when perfomance can be really improved in core, does it make sense
>>>>> to request for native support.
>>>>>>>
>>>>>>> Niels
>>>>>>>> Date: Sat, 16 Jul 2011 19:31:22 +0200
>>>>>>>> From: ntausc...@gmail.com
>>>>>>>> To: user@lists.neo4j.org
>>>>>>>> Subject: Re: [Neo4j] Hyperedges and Objects
>>>>>>>>
>>>>>>>> That's clear. Such mappings are more difficult to traverse since the
>>>>>>>> traverser has to know if there is such a hyper edge vertex. I'm
>>>>>>>> wondering if there is no need to provide an embedded solution for such
>>>>> a
>>>>>>>> transformation. Each user who is confronted with hyper edges has to
>>>>>>>> implement some kind of such mapping. It would be helpful, for example,
>>>>>>>> if each Neo4j relationship can manage hyper edges automatically and
>>>>>>>> provide an additional 'isHyper' method pointing out that there are
>>>>>>>> additional methods allowing to get all further incident nodes. This is
>>>>>>>> also a matter of performance. I think such a handling is implemented
>>>>>>>> most efficiently within the Neo4j engine.
>>>>>>>>
>>>>>>>> Best regards
>>>>>>>>
>>>>>>>> Norbert Tausch
>>>>>>>>
>>>>>>>> Am 16.07.2011 00:52, schrieb Niels Hoogeveen:
>>>>>>>>> Hyper edges can be emulated.
>>>>>>>>> Suppose you want to store the fact "John gives Pete a book".
>>>>>>>>> This is indeed a ternary relationship, which would call for an hyper
>>>>> edge.
>>>>>>>>> This fact can be stored as follows:
>>>>>>>>> Some act of giving --Giver-->JohnSome act of giving --Recipient-->
>>>>> PeteSome act of giving --Gift--> book
>>>>>>>>> N-ary relationships can generally be decomposed into N binary
>>>>> relationships, where a central node is used to used as a placeholder for
>>>>> the
>>>>> N-ary relationship.
>>>>>>>>> Complex types can either be stored into a byte array or if
>>>>> appropriate in multiple properties.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Date: Sat, 16 Jul 2011 00:04:15 +0200
>>>>>>>>>> From: ntausc...@gmail.com
>>>>>>>>>> To: user@lists.neo4j.org
>>>>>>>>>> Subject: [Neo4j] Hyperedges and Objects
>>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> is there a possibility to store hyper edges in Neo4j? Is there a
>>>>> plan to
>>>>>>>>>> implement this?
>>>>>>>>>>
>>>>>>>>>> Will Neo4j get the ability to store complex types in addition to
>>>>>>>>>> primitve data types for properties of nodes and relationships?
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> Best regards
>>>>>>>>>>
>>>>>>>>>> Norbert Tausch
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
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>>>>
>>>>
>>>>
>>>> --
>>>> Mattias Persson, [matt...@neotechnology.com]
>>>> Hacker, Neo Technology
>>>> www.neotechnology.com
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