RE: [External] [xdi] One change to multiplicity proposal

Btw, XGP is nothing special, just basic triple pattern matching combined with the following operators $and, $or, $not, $xor, $not, $nand. For example the XGP for a person who knows =bob or =alice, but not charlie might be:

$and($$s/$is$a/+person)($or($$s/+knows/=bob)($$s/+knows/=alice))($not($$s/+knows/=charlie))

FWIW, I realize $is$a is incorrect per current $words, is legacy code of mine that uses $is$a to indicate instance of and I don’t remember current correct $word off the top of my head right now. Also realize the above may not be correct per current multiplicity proposal.

Kind regards,

Bill Barnhill

Booz Allen Hamilton - Belcamp,MD

barnhill_william@bah.com

Cell: 1-443-924-0824

Desk: 1-443-861-9102

From: xdi@lists.oasis-open.org [mailto:xdi@lists.oasis-open.org] On Behalf Of Barnhill, William [USA]
Sent: Friday, September 28, 2012 2:57 PM
To: OASIS - XDI TC
Subject: [xdi] RE: [External] [xdi] One change to multiplicity proposal

Some thoughts for our query language are below. These are taken from a comparison of two Neo4j graph query languages, Cypher and Gremlin, posted at http://romikoderbynew.com/2012/02/22/gremlin-vs-cypher-initial-thoughts-neo4j/.

· Simple graph traversals are much more efficient when using Gremlin

· Queries in Gremlin are 30-50% faster for simple traversals

· Cypher is ideal for complex traversals where back tracking is required

· Cypher is our choice of query language for reporting

· Gremlin is our choice of query language for simple traversals where projections are not required

· Cypher has intrinsic table projection model, where Gremlins table projection model relies on AS steps which can be cumbersome when backtracking e.g. Back(), As() and _CopySplit, where cypher is just comma separated matches

· Cypher is much better suited for outer joins than Gremlin, to achieve similar results in gremlin requires parallel querying with CopySplit, where as in Cypher using the Match clause with optional relationships

· Gremlin is ideal when you need to retrieve very simple data structures

· Table projection in gremlin can be very powerful, however outer joins can be very verbose

An example of Cypher

var resultSet = graphClient.RootNode

.StartCypher("root")

.Match(@"root-[:HOSTS]->(agency)

<-[:USER_BELONGS_TO]-(user)-[:USER_LINKED_TO_PROGRAM]

->(program)

<-[:HAS_PROGRAM]-(centre),

(program)<-[:HAS_SUGGESTED_PROGRAM]-(referralDecisionsSection)

<-[:REFERRAL_HAS_DECISIONS_SECTION]-(referral)-[:CREATED_BY]

->(createdByUser), (referral)-[:REFERRAL_HAS_WHO_SECTION]

->(whoSection)-[:HAS_PARTICIPANT]->(participant)")

.Where<Agency>(agency => agency.Key == userIdentifier.AgencyKey)

.And()

.Where<User>(user => user.Username == userIdentifier.Username)

.And()

.Where<Referral>(referral => referral.Completed == false)

.Return((user, program, centre, createdByUser, referral, whoSection, participant) =>

new ReferralByGroup

{

UserFamilyName = createdByUser.As<User>().FamilyName,

UserGivenName = createdByUser.As<User>().GivenName,

Program = program.As<Program>().Name,

Centre = centre.As<Centre>().Name,

ReferralId = referral.As<Referral>().UniqueId,

ReferralDate = whoSection.As<ReferralWhoSection>().ReferralDate,

ParticipantName = participant.As<ReferralParticipant>().Name,

ParticipantDisplayOrder = participant.As<ReferralParticipant>().DisplayOrder,

})

.Results

.ToArray();

An equivalent in Gremlin:

var resultSet = graphClient

.RootNode

.Out<Agency>(Hosts.TypeKey, a => a.Key == userIdentifier.AgencyKey)

.In<User>(UserBelongsTo.TypeKey, u => u.Username == userIdentifier.Username)

.Out<Program>(UserLinkedToProgram.TypeKey)

.As("Program")

.In<Centre>(HasProgram.TypeKey)

.As("Centre")

.BackV<Program>("Program")

.In<ReferralDecisionsSection>(HasSuggestedProgram.TypeKey)

.In<Referral>(ReferralHasDecisionsSection.TypeKey, r => r.Completed == false)

.As("ReferralId")

.Out<User>(CreatedBy.TypeKey)

.As("UserGivenName")

.As("UserFamilyName")

.BackV<Referral>("ReferralId")

.Out<ReferralWhoSection>(ReferralHasWhoSection.TypeKey)

.As("ReferralDate")

.Out<ReferralParticipant>(HasParticipant.TypeKey)

.As("ParticipantDisplayOrder")

.As("ParticipantName")

.Table

<ReferralByGroup, Program, Centre, Referral, User, User, ReferralWhoSection, ReferralParticipant,

ReferralParticipant>(

program => program.Name,

centre => centre.Name,

referral => referral.UniqueId,

user => user.FamilyName,

user => user.GivenName,

who => who.ReferralDate,

participant => participant.Name,

participant => participant.DisplayOrder

)