Nested Properties support in JanusGraph

[Debasish Kanhar]

Hi,

I know about meta properties, and can add them using:
http://tinkerpop.apache.org/docs/current/reference/#vertex-properties

But I'm able to add properties only till 2 levels. i.e. I'm able to add meta properties to properties but is there way to add meta properties to meta properties? I followed the following query:

gremlin> v = g.addV().property('name','marko').property('name','marko a. rodriguez').next()

gremlin> g.V(v).properties().property('date',2014)
==>vp[name->marko a. rodriguez]

gremlin> g.V(v).properties().properties().property('date1',2015)
org.janusgraph.graphdb.relations.SimpleJanusGraphProperty cannot be cast to org.apache.tinkerpop.gremlin.structure.Element
Type ':help' or ':h' for help.
Display stack trace? [yN]

Is there a way to add properties of properties?

Also, I'm playing around with Cardinality, and I want to make a Vertex property as List of Key-value pairs:
The structure in my client (Python) is as follows:

ARTICLES: [
                {
                    ARTICLE_ID: 12345,
                    ARTICLE_TITLE: Text,
                    ARTICLE_URL: Text,
                    PRIMARY_SOURCE: Text,
                    SECONDARY_SOURCE: Text,
                    ARTICLE_PUBLISHED_DATE: Text    
                },
                {
                    ARTICLE_ID: 12346,
                    ARTICLE_TITLE: Text,
                    ARTICLE_URL: Text,
                    PRIMARY_SOURCE: Text,
                    SECONDARY_SOURCE: Text,
                    ARTICLE_PUBLISHED_DATE: Text       
                }
        ]

Is there any possible way to address this? I tried doing Cardinality, but it also expects Data type to be specified, and JanusGraph native data types are normal objects like Int, Long but not any standard Key-Value pairs.

My following query returned me error while Schema Generation:

gremlin> caseInfos = mgmt.makePropertyKey('caseInfos').cardinality(Cardinality.LIST).make()
Need to specify a datatype
Type ':help' or ':h' for help.
Display stack trace? [yN]

These data types seems like basic support needed and if there are any suggestions on how to approach such data structure, all suggestions are really helpful

Thanks

[Florian Hockmann]

Hi Debasish,

no, adding meta-properties to meta-properties is not possible (at least not to my knowledge). When you just start with a new schema then I would also strongly consider if you really need meta-properties at all as they might not be supported anymore in TinkerPop 4 as Marko wrote at Gremlin-users:

 I also believe we should get rid of multi- and meta-properties and get back to TinkerPop2 data structure semantics. 

The same applies to multi-properties, but can't you simply model the properties ARTICLE_ID, ARTICLE_TITLE, ARTICLE_URL, and so on as normal properties?

[Debasish Kanhar]

Hi Florian,

Thanks for response. So if my understanding is correct then Tinkerpop 4 might remove Multi Properties (Same key storing separate values) and meta properties (Key-value pair inside a key) right? That is going to be huge loss.

As per your question, can I model my properties in better way? I don't seem to find a better way, and if you can suggest it will be great.

So my each node is Entity node. Each entity can be fetched from N number of articles. So, basically for each entity/node I'll have multiple Article_ID, Article_Title etc as its properties corresponding to each source of article. The only way I could think to implement this data structure is to have either List of Multi properties. If you have any suggestion to model this data structure please let me know.

[Antriksh Shah]

Hey Debashish,

Is there any particular reason why you are going ahead with a graph database for this usecase?

Moreover I got confused between entities and articles. Could you please explain these two.

If my understanding is correct, could you have a vertex call entity and a vertex called article. Those properties of articles which can help fetch entity could go as the edge property.

So two vertex types -> entity and articles. 

Since articles help look up vertex-> those fields which help in the lookup become edge property.