x.ai a personal assistant who schedules meetings for you

MONGO WORLD 2015 NEW YORK CITY VISIT X.AI TO JOIN THE WAITLIST

Using MongoDB at x.ai

varun vijayaraghavan@xdotai

Magically Schedule Meetings

Just Cc: Amy@x.ai

Pain Solution Jane John Jane Amy@x.ai John

CC: Amy @ x.ai“Amy, please set something up for Jane and I next week.”

Product Characteristics

● Need quick response

● Supervised Learning requires large training data set

● # meetings scale linearly with # users

● 1 user meets with N people

● People share meeting, places, times and company

Technical challenges

● Natural language understanding with extremely high accuracy

● Natural conversation over email with people

● Complex data relationship

● Optimize for sparse data

● Speed of development and change

Stack

Queue Based Architecture

Modeling Meetings

Meetings

People

Places Times

1:N and N:N relationships across various collections

Modeling Meetings{

host : Participant,guests : [Participant],time : { start : Date,

end: Date, recurring: String},

timezone : String,duration : Number,locations : [Location],timeInitiated : Date,timeRescheduled: [Date],timeCompleted: Date,status : String,landmarks: [Landmark],activities: [Activity]…...

}

Embedding vs. Referencing

{ host : { name : {.....}, nicknames : [String], phones : [{Type: String}] primaryEmail : String, secondaryEmails : [String], title : String, signatures: [String], …... }, travelTime : String, status : String, timezone : String, duration : Number, …...}

{ host : Participant, travelTime : String, status : String, timezone : String, duration : Number, …...}

Participant { name : {.....}, nicknames : [String], phones : [{Type: String}] primaryEmail : String, secondaryEmails : [String], title : String, signatures: [String], …... },

Embedding ReferencingConsiderations

● Query patterns

● Access to embedded doc

● # references to a doc

● Application level join

● 1-way or 2-way referencing

Assistant is a PERSON Assistant is an Attribute of PERSON

Assistant is a PROFILE, a separate and smaller

entity

Modeling someone’s assistant1st try 2nd try 3rd try

{ name : {.....}, nicknames : [String], phones : [{Type: String}] primaryEmail : String, secondaryEmails : [String], title : String, signatures: [String] …...}

{ name : { first : String, last: String }, primaryEmail : String }

{ name : {.....}, nicknames : [String], phones : [{Type: String}] primaryEmail : String, secondaryEmails : [String], title : String, signatures: [String], assistant : { name : {.....}, primaryEmail : String } …...}

Dealing with schema changes

Issues

● Inconsistent character offsets

● Inconsistent time representation

● Improper sent date (yr 2026)

● Key info not saved

Fixes

● Recalculate character offsets

● Reconstruct time entities

● Recalculate timezone based on context

● Filter out unsalvageable data

Schemaless vs. Typesafe

● Discrepancy between models in Scala versus stored data in mongo.

○ MongoDB stores free form nested structures

○ Scala relies on strict, type safed models for data

● Models in flux

○ Data extraction (write) vs. decision making (read) formats

○ We are continuously learning new edge case about scheduling meetings

Mongoose

● A very nice object modeling and querying library for mongodb with node.js.

● Client side schema layer

● Useful features

○ Data validation

○ “Virtual” fields

○ Nested documents with automatic _id reference

○ Client side joins across collections and databases

Interactive Applications Architecture

Internal API powered by express-restify-mongo provides a plug-n-play API layer for mongoose and MongoDB

Model evolution with mongoose

{ host : Participant guests : [Participant] ... activity: String ...}

Meeting Format in Mongo

Activity Model

New Scala Model for Meeting

case class Meeting (host: Participantguests:

List[Participant]...activities:

List[Activity]...

)

case class Meeting (host: Participantguests:

List[Participant]...activity: String...

)

case class Activity (id: String,activity: String

)

Initial Scala Model for Meeting

Ease transition with Virtual field

MeetingSchema.virtual( "activities" ).get( function() { var virtualActivity = { id: randomString(), activity: this.activity } return [virtualActivity];});

Feeding data science

ML training architecture

Using Mongo for ML: What we need

● Heavy on experimentation○ Need to train on different parameters, algorithms, data sets

● Nested data sets that are dependent on the specific experiment○ Emails have several feature types, each of which have several

parameters

● Mongo models to work well with Scala models

Using Mongo for ML: The beginning

{"messageId":"<somerandommessage@xxxx>",

"classes" : ["A", "B", "C"],

"featureVector" : [ [

"OneGrams", [ { "work" : 3 }, { "that" : 1 }, … ] ],

[ "TwoGrams",

[ { "that work" : 1 }, { "you then" : 1 }, ]],...

}

case class Features (messageId: String,classes: List[String],featureVector:

List[Tuple2[String, List[Map[String, Integer]]]])

Scala

Mongo

Mongo for ML: Make it work with Scala

{ "messageId" : "<somerandommessage@xxxx>", "classifierLabels" : [ { "classifier" : "MeetingClassifier", "class" : "A" } ], "featureVector" : [ { "featureType" : "TaggedOneGram", "featureKeys" : [ { "featureKey" : "work", "featureValue" : 3 }, { "featureKey" : "that", "featureValue" : 1 }, ... ] }, ... ]}

case class Features (messageId: String,classes: List[Classes],featureVector:

List[FeatureVectors])

case class Classes (classifier: String,class: String

)

case class FeatureVectors(featureType: String,featureKeys: List[FeatureKeys]

)

case class FeatureKey(featureKey: String,featureValue: 1

)

ScalaMongo

varun @ human.x.aibackend engineer

25 Broadway. 9th FloorNew York, 10004 NY

E: hello@x.aiT: @xdotai

Visit x.ai to join the waitlist