diff --git a/src/aquarius/Aquarius.ts b/src/aquarius/Aquarius.ts
index abe61cb..cc3766e 100644
--- a/src/aquarius/Aquarius.ts
+++ b/src/aquarius/Aquarius.ts
@@ -1,5 +1,5 @@
-import {URL} from "whatwg-url"
-import DDO from "../ddo/DDO"
+import { URL } from "whatwg-url"
+import { DDO } from "../ddo/DDO"
 import Config from "../models/Config"
 import DID from "../ocean/DID"
 import Logger from "../utils/Logger"
diff --git a/src/ddo/AdditionalInformation.ts b/src/ddo/AdditionalInformation.ts
deleted file mode 100644
index c4878eb..0000000
--- a/src/ddo/AdditionalInformation.ts
+++ /dev/null
@@ -1,39 +0,0 @@
-import StructuredMarkup from "./StructuredMarkup"
-
-/**
- * Additional Information of Assets Metadata.
- * @see https://github.com/oceanprotocol/OEPs/tree/master/8#additional-information
- */
-export default class AdditionalInformation {
-    /**
-     * An indication of update latency - i.e. How often are updates expected (seldom,
-     * annually, quarterly, etc.), or is the resource static that is never expected
-     * to get updated.
-     * @type {string}
-     * @example "yearly"
-     */
-    public updateFrecuency: string = "yearly"
-
-    /**
-     * A link to machine-readable structured markup (such as ttl/json-ld/rdf)
-     * describing the dataset.
-     * @type {StructuredMarkup[]}
-     */
-    public structuredMarkup: StructuredMarkup[] = [
-        {
-            uri: "http://skos.um.es/unescothes/C01194/jsonld",
-            mediaType: "application/ld+json",
-        } as StructuredMarkup,
-        {
-            uri: "http://skos.um.es/unescothes/C01194/turtle",
-            mediaType: "text/turtle",
-        } as StructuredMarkup,
-    ]
-
-    /**
-     * Checksum of attributes to be able to compare if there are changes in
-     * the asset that you are purchasing.
-     * @type {string}
-     */
-    public checksum: string
-}
diff --git a/src/ddo/Authentication.ts b/src/ddo/Authentication.ts
index bd4689a..b5e1869 100644
--- a/src/ddo/Authentication.ts
+++ b/src/ddo/Authentication.ts
@@ -1,4 +1,4 @@
-export default class Authentication {
-    public type: string = "RsaSignatureAuthentication2018"
-    public publicKey: string = "did:op:123456789abcdefghi#keys-1"
+export interface Authentication {
+    public type: string
+    public publicKey: string
 }
diff --git a/src/ddo/Condition.ts b/src/ddo/Condition.ts
index ff88d89..e41168f 100644
--- a/src/ddo/Condition.ts
+++ b/src/ddo/Condition.ts
@@ -1,15 +1,48 @@
-import Dependency from "./Dependency"
-import Event from "./Event"
-import Parameter from "./Parameter"
+import { Event } from "./Event"
 
-export default class Condition {
-    public name: string
-    public contractName: string = "AccessCondition"
-    public functionName: string = "lockPayment"
-    public timeout: number = 0
-    public conditionKey: string = "0x12122434"
-    public parameters: Parameter[]
-    public events: Event[]
-    public dependencies: Dependency[] = []
-    public isTerminalCondition: boolean = false
+export interface Parameter {
+    name: string
+    type: string
+    value: any
+}
+
+export interface Dependency {
+    /**
+     * @example "lockPayment"
+     */
+    name: string
+    /**
+     * @example 0
+     */
+    timeout: number
+}
+
+export interface Condition {
+    name: string
+    /**
+     * @example "AccessCondition"
+     */
+    contractName: string
+    /**
+     * @example "lockPayment"
+     */
+    functionName: string
+    /**
+     * @example 0
+     */
+    timeout: number
+    /**
+     * @example "0x12122434"
+     */
+    conditionKey: string
+    parameters: Parameter[]
+    events: Event[]
+    /**
+     * @example []
+     */
+    dependencies: Dependency[]
+    /**
+     * @example false
+     */
+    isTerminalCondition: boolean
 }
diff --git a/src/ddo/Contract.ts b/src/ddo/Contract.ts
index 0396a1a..208f79e 100644
--- a/src/ddo/Contract.ts
+++ b/src/ddo/Contract.ts
@@ -1,7 +1,7 @@
 import Event from "./Event"
 
-export default class Contract {
-    public contractName: string
-    public fulfillmentOperator: number
-    public events: Event[]
+export interface Contract {
+    contractName: string
+    fulfillmentOperator: number
+    events: Event[]
 }
diff --git a/src/ddo/Curation.ts b/src/ddo/Curation.ts
deleted file mode 100644
index 95e0cc0..0000000
--- a/src/ddo/Curation.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-/**
- * Curation attributes of Assets Metadata.
- * @see https://github.com/oceanprotocol/OEPs/tree/master/8#curation-attributes
- */
-export default class Curation {
-    /**
-     * Decimal value between 0 and 1. 0 is the default value.
-     * @type {number}
-     * @example 0.93
-     */
-    public rating: number = 0.93
-
-    /**
-     * Number of votes. 0 is the default value.
-     * @type {number}
-     * @example 123
-     */
-    public numVotes: number = 123
-
-    /**
-     * Schema applied to calculate the rating.
-     * @type {number}
-     * @example "Binary Votting"
-     */
-    public schema?: string = "Binary Votting"
-}
diff --git a/src/ddo/DDO.ts b/src/ddo/DDO.ts
index 94825b1..ee5c471 100644
--- a/src/ddo/DDO.ts
+++ b/src/ddo/DDO.ts
@@ -1,12 +1,13 @@
-import Authentication from "./Authentication"
-import PublicKey from "./PublicKey"
-import Service from "./Service"
+import { Authentication } from "./Authentication"
+import { PublicKey } from "./PublicKey"
+import { Service } from "./Service"
+import { Proof } from "./Proof"
 
 /**
  * DID Descriptor Object.
  * Contains all the data related to an asset.
  */
-export default class DDO {
+export class DDO {
 
     /**
      * Serializes the DDO object.
@@ -29,6 +30,7 @@ export default class DDO {
     }
 
     public "@context": string = "https://w3id.org/future-method/v1"
+
     /**
      * DID, descentralized ID.
      * @type {string}
@@ -37,13 +39,9 @@ export default class DDO {
     public publicKey: PublicKey[]
     public authentication: Authentication[]
     public service: Service[]
+    public proof: Proof
 
-    public constructor(ddo?: {
-        id?: string,
-        publicKey?: PublicKey[],
-        authentication?: Authentication[],
-        service?: Service[],
-    }) {
+    public constructor(ddo?: Partial<DDO>) {
         this.authentication = (ddo && ddo.authentication) || []
         this.id = (ddo && ddo.id) || null
         this.publicKey = (ddo && ddo.publicKey) || []
diff --git a/src/ddo/Dependency.ts b/src/ddo/Dependency.ts
deleted file mode 100644
index 2a824f6..0000000
--- a/src/ddo/Dependency.ts
+++ /dev/null
@@ -1,4 +0,0 @@
-export default class Dependency {
-    public name: string = "lockPayment"
-    public timeout: number = 0
-}
diff --git a/src/ddo/Event.ts b/src/ddo/Event.ts
index 2195acf..ac70afe 100644
--- a/src/ddo/Event.ts
+++ b/src/ddo/Event.ts
@@ -1,7 +1,20 @@
-import EventHandler from "./EventHandler"
-
-export default class Event {
-    public name: string
-    public actorType: string
-    public handler: EventHandler
+export interface EventHandler {
+    /**
+     * @example "serviceAgreement"
+     */
+    moduleName: string
+    /**
+     * @example "fulfillAgreement"
+     */
+    functionName: string
+    /**
+     * @example "0.1"
+     */
+    version: string
+}
+
+export interface Event {
+    name: string
+    actorType: string
+    handler: EventHandler
 }
diff --git a/src/ddo/EventHandler.ts b/src/ddo/EventHandler.ts
deleted file mode 100644
index 5819cda..0000000
--- a/src/ddo/EventHandler.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-export default class EventHandler {
-    public moduleName: string = "serviceAgreement"
-    public functionName: string = "fulfillAgreement"
-    public version: string = "0.1"
-}
diff --git a/src/ddo/MetaData.ts b/src/ddo/MetaData.ts
index 5d89388..6cfbee1 100644
--- a/src/ddo/MetaData.ts
+++ b/src/ddo/MetaData.ts
@@ -1,65 +1,209 @@
-import AdditionalInformation from "./AdditionalInformation"
-import Curation from "./Curation"
-import MetaDataBase from "./MetaDataBase"
-import StructuredMarkup from "./StructuredMarkup"
+/**
+ * Base attributes of Assets Metadata.
+ * @see https://github.com/oceanprotocol/OEPs/tree/master/8#base-attributes
+ */
+export class MetaDataBase {
 
-const base: MetaDataBase = {
-    name: "UK Weather information 2011",
-    type: "dataset",
-    description: "Weather information of UK including temperature and humidity",
-    size: "3.1gb",
-    dateCreated: "2012-02-01T10:55:11+00:00",
-    author: "Met Office",
-    license: "CC-BY",
-    copyrightHolder: "Met Office",
-    encoding: "UTF-8",
-    compression: "zip",
-    contentType: "text/csv",
-    // tslint:disable-next-line
-    workExample: "stationId,latitude,longitude,datetime,temperature,humidity423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68",
-    contentUrls: [
-        "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
-        "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
-    ],
-    links: [
-        {sample1: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-daily/"},
-        {sample2: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-averages-25km/"},
-        {fieldsDescription: "http://data.ceda.ac.uk/badc/ukcp09/"},
-    ],
-    inLanguage: "en",
-    tags: "weather, uk, 2011, temperature, humidity",
-    price: 10,
-} as MetaDataBase
+    /**
+     * Descriptive name of the Asset.
+     * @type {string}
+     * @example "UK Weather information 2011"
+     */
+    name: string
 
-const curation: Curation = {
-    rating: 0.93,
-    numVotes: 123,
-    schema: "Binary Votting",
-} as Curation
+    /**
+     * Type of the Asset. Helps to filter by the type of asset,
+     * initially ("dataset", "algorithm", "container", "workflow", "other").
+     * @type {string}
+     * @example "dataset"
+     */
+    type: "dataset" | "algorithm" | "container" | "workflow" | "other"
 
-const additionalInformation: AdditionalInformation = {
-    updateFrecuency: "yearly",
-    structuredMarkup: [
-        {
-            uri: "http://skos.um.es/unescothes/C01194/jsonld",
-            mediaType: "application/ld+json",
-        } as StructuredMarkup,
-        {
-            uri: "http://skos.um.es/unescothes/C01194/turtle",
-            mediaType: "text/turtle",
-        } as StructuredMarkup,
-    ],
-} as AdditionalInformation
+    /**
+     * Details of what the resource is. For a dataset, this attribute
+     * explains what the data represents and what it can be used for.
+     * @type {string}
+     * @example "Weather information of UK including temperature and humidity"
+     */
+    description?: string
 
-export default class MetaData {
+    /**
+     * The date on which the asset was created or was added.
+     * @type {string}
+     * @example "2012-10-10T17:00:000Z"
+     */
+    dateCreated: string
 
-    public additionalInformation: AdditionalInformation
-    public base: MetaDataBase
-    public curation: Curation
+    /**
+     * Size of the asset (e.g. 18MB). In the absence of a unit (MB, kB etc.), kB will be assumed.
+     * @type {string}
+     * @example "3.1gb"
+     */
+    size: string
 
-    constructor(metaData?: MetaData) {
-        this.additionalInformation = (metaData && metaData.additionalInformation) || additionalInformation
-        this.base = (metaData && metaData.base) || base
-        this.curation = (metaData && metaData.curation) || curation
-    }
+    /**
+     * Name of the entity generating this data (e.g. Tfl, Disney Corp, etc.).
+     * @type {string}
+     * @example "Met Office"
+     */
+    author: string
+
+    /**
+     * Short name referencing the license of the asset (e.g. Public Domain, CC-0, CC-BY, No License Specified, etc. ).
+     * If it's not specified, the following value will be added: "No License Specified".
+     * @type {string}
+     * @example "CC-BY"
+     */
+    license: string
+
+    /**
+     * The party holding the legal copyright. Empty by default.
+     * @type {string}
+     * @example "Met Office"
+     */
+    copyrightHolder?: string
+
+    /**
+     * File encoding.
+     * @type {string}
+     * @example "UTF-8"
+     */
+    encoding?: string
+
+    /**
+     * File compression (e.g. no, gzip, bzip2, etc).
+     * @type {string}
+     * @example "zip"
+     */
+    compression?: string
+
+    /**
+     * File format, if applicable.
+     * @type {string}
+     * @example "text/csv"
+     */
+    contentType: string
+
+    /**
+     * Example of the concept of this asset. This example is part
+     * of the metadata, not an external link.
+     * @type {string}
+     * @example "423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68"
+     */
+    workExample?: string
+
+    /**
+     * List of content URLs resolving the Asset files.
+     * @type {string | string[]}
+     * @example "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip"
+     */
+    contentUrls: string | string[]
+
+    /**
+     * Mapping of links for data samples, or links to find out more information.
+     * Links may be to either a URL or another Asset. We expect marketplaces to
+     * converge on agreements of typical formats for linked data: The Ocean Protocol
+     * itself does not mandate any specific formats as these requirements are likely
+     * to be domain-specific.
+     * @type {any[]}
+     * @example
+     * [
+     *    {
+     *      anotherSample: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-daily/",
+     *    },
+     *    {
+     *      fieldsDescription: "http://data.ceda.ac.uk/badc/ukcp09/",
+     *    },
+     *  ]
+     */
+    links?: {[name: string]: string}[]
+
+    /**
+     * The language of the content. Please use one of the language
+     * codes from the {@link https://tools.ietf.org/html/bcp47 IETF BCP 47 standard}.
+     * @type {String}
+     * @example "en"
+     */
+    inLanguage?: string
+
+    /**
+     * Keywords or tags used to describe this content. Multiple entries in a keyword
+     * list are typically delimited by commas. Empty by default.
+     * @type {String}
+     * @example "weather, uk, 2011, temperature, humidity"
+     */
+    tags?: string
+
+    /**
+     * Price of the asset.
+     * @type {String}
+     * @example 10
+     */
+    price: number
+}
+
+/**
+ * Curation attributes of Assets Metadata.
+ * @see https://github.com/oceanprotocol/OEPs/tree/master/8#curation-attributes
+ */
+export interface Curation {
+    /**
+     * Decimal value between 0 and 1. 0 is the default value.
+     * @type {number}
+     * @example 0.93
+     */
+    rating: number
+
+    /**
+     * Number of votes. 0 is the default value.
+     * @type {number}
+     * @example 123
+     */
+    numVotes: number
+
+    /**
+     * Schema applied to calculate the rating.
+     * @type {number}
+     * @example "Binary Votting"
+     */
+    schema?: string
+}
+
+/**
+ * Additional Information of Assets Metadata.
+ * @see https://github.com/oceanprotocol/OEPs/tree/master/8#additional-information
+ */
+export interface AdditionalInformation {
+    /**
+     * An indication of update latency - i.e. How often are updates expected (seldom,
+     * annually, quarterly, etc.), or is the resource static that is never expected
+     * to get updated.
+     * @type {string}
+     * @example "yearly"
+     */
+    updateFrecuency: string
+
+    /**
+     * A link to machine-readable structured markup (such as ttl/json-ld/rdf)
+     * describing the dataset.
+     * @type {StructuredMarkup[]}
+     */
+    structuredMarkup: {
+        uri: string
+        mediaType: string
+    }[]
+
+
+    /**
+     * Checksum of attributes to be able to compare if there are changes in
+     * the asset that you are purchasing.
+     * @type {string}
+     */
+    checksum: string
+}
+
+export interface MetaData {
+    additionalInformation: AdditionalInformation
+    base: MetaDataBase
+    curation: Curation
 }
diff --git a/src/ddo/MetaDataBase.ts b/src/ddo/MetaDataBase.ts
deleted file mode 100644
index a20aad6..0000000
--- a/src/ddo/MetaDataBase.ts
+++ /dev/null
@@ -1,147 +0,0 @@
-/**
- * Base attributes of Assets Metadata.
- * @see https://github.com/oceanprotocol/OEPs/tree/master/8#base-attributes
- */
-export default class MetaDataBase {
-
-    /**
-     * Descriptive name of the Asset.
-     * @type {string}
-     * @example "UK Weather information 2011"
-     */
-    public name: string = "UK Weather information 2011"
-
-    /**
-     * Type of the Asset. Helps to filter by the type of asset,
-     * initially ("dataset", "algorithm", "container", "workflow", "other").
-     * @type {string}
-     * @example "dataset"
-     */
-    public type: "dataset" | "algorithm" | "container" | "workflow" | "other" = "dataset"
-
-    /**
-     * Details of what the resource is. For a dataset, this attribute
-     * explains what the data represents and what it can be used for.
-     * @type {string}
-     * @example "Weather information of UK including temperature and humidity"
-     */
-    public description?: string = "Weather information of UK including temperature and humidity"
-
-    /**
-     * The date on which the asset was created or was added.
-     * @type {string}
-     * @example "2012-10-10T17:00:000Z"
-     */
-    public dateCreated: string = "2012-10-10T17:00:000Z"
-
-    /**
-     * Size of the asset (e.g. 18MB). In the absence of a unit (MB, kB etc.), kB will be assumed.
-     * @type {string}
-     * @example "3.1gb"
-     */
-    public size: string = "3.1gb"
-
-    /**
-     * Name of the entity generating this data (e.g. Tfl, Disney Corp, etc.).
-     * @type {string}
-     * @example "Met Office"
-     */
-    public author: string = "Met Office"
-
-    /**
-     * Short name referencing the license of the asset (e.g. Public Domain, CC-0, CC-BY, No License Specified, etc. ).
-     * If it's not specified, the following value will be added: "No License Specified".
-     * @type {string}
-     * @example "CC-BY"
-     */
-    public license: string = "CC-BY"
-
-    /**
-     * The party holding the legal copyright. Empty by default.
-     * @type {string}
-     * @example "Met Office"
-     */
-    public copyrightHolder?: string = "Met Office"
-
-    /**
-     * File encoding.
-     * @type {string}
-     * @example "UTF-8"
-     */
-    public encoding?: string = "UTF-8"
-
-    /**
-     * File compression (e.g. no, gzip, bzip2, etc).
-     * @type {string}
-     * @example "zip"
-     */
-    public compression?: string = "zip"
-
-    /**
-     * File format, if applicable.
-     * @type {string}
-     * @example "text/csv"
-     */
-    public contentType: string = "text/csv"
-
-    /**
-     * Example of the concept of this asset. This example is part
-     * of the metadata, not an external link.
-     * @type {string}
-     * @example "423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68"
-     */
-    public workExample?: string = "423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68"
-
-    /**
-     * List of content URLs resolving the Asset files.
-     * @type {string | string[]}
-     * @example "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip"
-     */
-    public contentUrls: string | string[] = [
-        "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
-        "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
-    ]
-
-    /**
-     * Mapping of links for data samples, or links to find out more information.
-     * Links may be to either a URL or another Asset. We expect marketplaces to
-     * converge on agreements of typical formats for linked data: The Ocean Protocol
-     * itself does not mandate any specific formats as these requirements are likely
-     * to be domain-specific.
-     * @type {any[]}
-     */
-    public links?: any[] = [
-        {
-            sample1: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-daily/",
-        },
-        {
-            sample2: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-averages-25km/",
-        },
-        {
-            fieldsDescription: "http://data.ceda.ac.uk/badc/ukcp09/",
-        },
-    ]
-
-    /**
-     * The language of the content. Please use one of the language
-     * codes from the {@link https://tools.ietf.org/html/bcp47 IETF BCP 47 standard}.
-     * @type {String}
-     * @example "en"
-     */
-    public inLanguage?: string = "en"
-
-    /**
-     * Keywords or tags used to describe this content. Multiple entries in a keyword
-     * list are typically delimited by commas. Empty by default.
-     * @type {String}
-     * @example "weather, uk, 2011, temperature, humidity"
-     */
-    public tags?: string = "weather, uk, 2011, temperature, humidity"
-
-    /**
-     * Price of the asset.
-     * @type {String}
-     * @example 10
-     */
-    public price: number = 10
-}
diff --git a/src/ddo/Parameter.ts b/src/ddo/Parameter.ts
deleted file mode 100644
index d067ed2..0000000
--- a/src/ddo/Parameter.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-export default class Parameter {
-    public name: string
-    public type: string
-    public value: any
-}
diff --git a/src/ddo/Proof.ts b/src/ddo/Proof.ts
new file mode 100644
index 0000000..c482b70
--- /dev/null
+++ b/src/ddo/Proof.ts
@@ -0,0 +1,6 @@
+export interface Proof {
+    type: string
+    created: string
+    creator: string
+    signatureValue: string
+}
diff --git a/src/ddo/PublicKey.ts b/src/ddo/PublicKey.ts
index 81bf2f6..08d111c 100644
--- a/src/ddo/PublicKey.ts
+++ b/src/ddo/PublicKey.ts
@@ -1,7 +1,28 @@
-export default class PublicKey {
-    public id: string = "did:op:123456789abcdefghi#keys-1"
-    public type: string = "Ed25519VerificationKey2018"
-    public owner: string = "did:op:123456789abcdefghi"
-    public publicKeyPem?: string = "-----BEGIN PUBLIC KEY...END PUBLIC KEY-----\r\n"
-    public publicKeyBase58?: string = "H3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV"
+/**
+ * Public key data.
+ */
+export interface PublicKey {
+    /**
+     * ID of the key.
+     * @type {string}
+     * @example "did:op:123456789abcdefghi#keys-1"
+     */
+    id: string
+
+    /**
+     * Type of key.
+     * @type {string}
+     */
+    type: 'Ed25519VerificationKey2018' | 'RsaVerificationKey2018' | 'EdDsaSAPublicKeySecp256k1'
+
+    /**
+     * Key owner.
+     * @type {string}
+     * @example "did:op:123456789abcdefghi"
+     */
+    owner: string
+
+    publicKeyPem?: string
+    publicKeyBase58?: string
+    publicKeyHex?: string
 }
diff --git a/src/ddo/Service.ts b/src/ddo/Service.ts
index 4891d39..51da0a0 100644
--- a/src/ddo/Service.ts
+++ b/src/ddo/Service.ts
@@ -1,15 +1,15 @@
-import Condition from "./Condition"
-import Contract from "./Contract"
-import MetaData from "./MetaData"
+import { Condition } from "./Condition"
+import { Contract } from "./Contract"
+import { MetaData } from "./MetaData"
 
-export default class Service {
-    public type: string = "OpenIdConnectVersion1.0Service"
-    public serviceDefinitionId?: string
-    public templateId?: string
-    public serviceEndpoint: string = "https://openid.example.com/"
-    public purchaseEndpoint?: string
-    public description?: string = "My public social inbox"
-    public metadata?: MetaData = {} as MetaData
-    public serviceAgreementContract?: Contract
-    public conditions?: Condition[] = []
+export interface Service {
+    type: string
+    serviceDefinitionId?: string
+    templateId?: string
+    serviceEndpoint: string
+    purchaseEndpoint?: string
+    description?: string
+    metadata?: MetaData
+    serviceAgreementContract?: Contract
+    conditions?: Condition[]
 }
diff --git a/src/ddo/StructuredMarkup.ts b/src/ddo/StructuredMarkup.ts
deleted file mode 100644
index acf0c16..0000000
--- a/src/ddo/StructuredMarkup.ts
+++ /dev/null
@@ -1,4 +0,0 @@
-export default class StructuredMarkup {
-    public uri: string = "http://skos.um.es/unescothes/C01194/jsonld"
-    public mediaType: string = "application/ld+json"
-}
diff --git a/src/examples/config/config.json b/src/examples/config/config.json
index b837e59..34f5721 100644
--- a/src/examples/config/config.json
+++ b/src/examples/config/config.json
@@ -1,6 +1,6 @@
 {
   "nodeUri": "http://localhost:8545",
-  "aquariusUri": "http://aquarius.dev-ocean.com:5000",
+  "aquariusUri": "https://nginx-aquarius.dev-ocean.com",
   "brizoUri": "http://localhost:8030",
   "parityUri": "http://localhost:9545",
   "secretStoreUri": "http://localhost:12001",
diff --git a/src/ocean/OceanAssets.ts b/src/ocean/OceanAssets.ts
index 4b38632..9e6318e 100644
--- a/src/ocean/OceanAssets.ts
+++ b/src/ocean/OceanAssets.ts
@@ -1,15 +1,10 @@
 import AquariusProvider from "../aquarius/AquariusProvider"
 import SearchQuery from "../aquarius/query/SearchQuery"
 import BrizoProvider from "../brizo/BrizoProvider"
-import Authentication from "../ddo/Authentication"
-import Condition from "../ddo/Condition"
-import Contract from "../ddo/Contract"
-import DDO from "../ddo/DDO"
-import Event from "../ddo/Event"
-import EventHandler from "../ddo/EventHandler"
-import MetaData from "../ddo/MetaData"
-import PublicKey from "../ddo/PublicKey"
-import Service from "../ddo/Service"
+import { Condition } from "../ddo/Condition"
+import { DDO } from "../ddo/DDO"
+import { MetaData } from "../ddo/MetaData"
+import { Service } from "../ddo/Service"
 import ContractEvent from "../keeper/Event"
 import EventListener from "../keeper/EventListener"
 import Keeper from "../keeper/Keeper"
@@ -88,7 +83,7 @@ export default class OceanAssets {
             authentication: [{
                 type: "RsaSignatureAuthentication2018",
                 publicKey: did.getDid() + "#keys-1",
-            } as Authentication],
+            }],
             id: did.getDid(),
             publicKey: [
                 {
@@ -96,7 +91,7 @@ export default class OceanAssets {
                     type: "Ed25519VerificationKey2018",
                     owner: did.getDid(),
                     publicKeyBase58: await publisher.getPublicKey(),
-                } as PublicKey,
+                },
             ],
             service: [
                 {
@@ -118,24 +113,24 @@ export default class OceanAssets {
                                     moduleName: "payment",
                                     functionName: "lockPayment",
                                     version: "0.1",
-                                } as EventHandler,
-                            } as Event,
+                                },
+                            },
                         ],
-                    } as Contract,
+                    },
                     conditions,
-                } as Service,
+                },
                 {
                     type: "Compute",
                     serviceEndpoint: brizo.getComputeEndpoint(publisher.getId(),
                         computeServiceDefintionId, "xxx", "xxx"),
                     serviceDefinitionId: computeServiceDefintionId,
-                } as Service,
+                },
                 {
                     type: "Metadata",
                     serviceEndpoint,
                     serviceDefinitionId: metadataServiceDefinitionId,
                     metadata,
-                } as Service,
+                },
             ],
         })
 
diff --git a/test/aquarius/Aquarius.test.ts b/test/aquarius/Aquarius.test.ts
index f3a2868..08e11f9 100644
--- a/test/aquarius/Aquarius.test.ts
+++ b/test/aquarius/Aquarius.test.ts
@@ -1,7 +1,7 @@
 import * as assert from "assert"
 import Aquarius from "../../src/aquarius/Aquarius"
 import SearchQuery from "../../src/aquarius/query/SearchQuery"
-import DDO from "../../src/ddo/DDO"
+import { DDO } from "../../src/ddo/DDO"
 import DID from "../../src/ocean/DID"
 import WebServiceConnectorProvider from "../../src/utils/WebServiceConnectorProvider"
 import config from "../config"
@@ -10,6 +10,7 @@ import WebServiceConnectorMock from "../mocks/WebServiceConnector.mock"
 describe("Aquarius", () => {
 
     const aquarius: Aquarius = new Aquarius(config)
+
     describe("#queryMetadata()", () => {
 
         const query = {
@@ -40,6 +41,7 @@ describe("Aquarius", () => {
             WebServiceConnectorProvider.setConnector(new WebServiceConnectorMock([new DDO()]))
 
             const result: DDO[] = await aquarius.queryMetadata(query)
+            console.log(result)
             assert(result)
             assert(result[0].findServiceById)
         })
diff --git a/test/ddo/DDO.test.ts b/test/ddo/DDO.test.ts
index 8d24fd6..c47826f 100644
--- a/test/ddo/DDO.test.ts
+++ b/test/ddo/DDO.test.ts
@@ -1,13 +1,9 @@
 import {assert} from "chai"
-import AdditionalInformation from "../../src/ddo/AdditionalInformation"
-import Authentication from "../../src/ddo/Authentication"
-import Curation from "../../src/ddo/Curation"
-import DDO from "../../src/ddo/DDO"
-import MetaData from "../../src/ddo/MetaData"
-import MetaDataBase from "../../src/ddo/MetaDataBase"
-import PublicKey from "../../src/ddo/PublicKey"
-import Service from "../../src/ddo/Service"
-import StructuredMarkup from "../../src/ddo/StructuredMarkup"
+import { Authentication} from "../../src/ddo/Authentication"
+import { DDO } from "../../src/ddo/DDO"
+import { MetaData, MetaDataBase, Curation, AdditionalInformation } from "../../src/ddo/MetaData"
+import { PublicKey } from "../../src/ddo/PublicKey"
+import { Service } from "../../src/ddo/Service"
 import * as jsonDDO from "../testdata/ddo.json"
 
 describe("DDO", () => {
@@ -26,12 +22,6 @@ describe("DDO", () => {
                 owner: "did:op:123456789abcdefghi",
                 publicKeyBase58: "H3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV",
             } as PublicKey,
-            {
-                id: "did:op:123456789abcdefghi#keys-3",
-                type: "RsaPublicKeyExchangeKey2018",
-                owner: "did:op:123456789abcdefghi",
-                publicKeyPem: "-----BEGIN PUBLIC KEY...END PUBLIC KEY-----\r\n",
-            } as PublicKey,
         ],
         authentication: [
             {
@@ -137,11 +127,11 @@ describe("DDO", () => {
                             {
                                 uri: "http://skos.um.es/unescothes/C01194/jsonld",
                                 mediaType: "application/ld+json",
-                            } as StructuredMarkup,
+                            },
                             {
                                 uri: "http://skos.um.es/unescothes/C01194/turtle",
                                 mediaType: "text/turtle",
-                            } as StructuredMarkup,
+                            },
                         ],
                     } as AdditionalInformation,
                 } as MetaData,
diff --git a/test/mocks/Aquarius.mock.ts b/test/mocks/Aquarius.mock.ts
index 5418c9d..23e9e09 100644
--- a/test/mocks/Aquarius.mock.ts
+++ b/test/mocks/Aquarius.mock.ts
@@ -1,5 +1,5 @@
 import Aquarius from "../../src/aquarius/Aquarius"
-import DDO from "../../src/ddo/DDO"
+import { DDO } from "../../src/ddo/DDO"
 import DID from "../../src/ocean/DID"
 
 const ddoStore: Map<string, any> = new Map<string, any>()
diff --git a/test/ocean/Ocean.test.ts b/test/ocean/Ocean.test.ts
index 986793c..ed1be31 100644
--- a/test/ocean/Ocean.test.ts
+++ b/test/ocean/Ocean.test.ts
@@ -3,9 +3,8 @@ import AquariusProvider from "../../src/aquarius/AquariusProvider"
 import SearchQuery from "../../src/aquarius/query/SearchQuery"
 import BrizoProvider from "../../src/brizo/BrizoProvider"
 import ConfigProvider from "../../src/ConfigProvider"
-import DDO from "../../src/ddo/DDO"
-import MetaData from "../../src/ddo/MetaData"
-import Service from "../../src/ddo/Service"
+import { DDO } from "../../src/ddo/DDO"
+import { Service } from "../../src/ddo/Service"
 import Account from "../../src/ocean/Account"
 import Ocean from "../../src/ocean/Ocean"
 import ServiceAgreement from "../../src/ocean/ServiceAgreements/ServiceAgreement"
@@ -17,6 +16,7 @@ import AquariusMock from "../mocks/Aquarius.mock"
 import BrizoMock from "../mocks/Brizo.mock"
 import SecretStoreMock from "../mocks/SecretStore.mock"
 import WebServiceConnectorMock from "../mocks/WebServiceConnector.mock"
+import { metadataMock } from "../testdata/MetaData"
 
 let ocean: Ocean
 let accounts: Account[]
@@ -24,6 +24,8 @@ let testPublisher: Account
 
 describe("Ocean", () => {
 
+    const metadata = metadataMock
+
     before(async () => {
         ConfigProvider.setConfig(config)
         AquariusProvider.setAquarius(new AquariusMock(config))
@@ -37,7 +39,6 @@ describe("Ocean", () => {
     })
 
     describe("#getInstance()", () => {
-
         it("should get an instance of cean", async () => {
 
             const oceanInstance: Ocean = await Ocean.getInstance(config)
@@ -47,7 +48,6 @@ describe("Ocean", () => {
     })
 
     describe("#getAccounts()", () => {
-
         it("should list accounts", async () => {
 
             const accs: Account[] = await ocean.getAccounts()
@@ -56,30 +56,22 @@ describe("Ocean", () => {
             assert(0 === (await accs[5].getBalance()).ocn)
             assert("string" === typeof accs[0].getId())
         })
-
     })
 
     describe("#resolveDID()", () => {
-
         it("should resolve a did to a ddo", async () => {
-
-            const metaData: MetaData = new MetaData()
-            const ddo: DDO = await ocean.registerAsset(metaData, testPublisher)
+            const ddo: DDO = await ocean.registerAsset(metadata, testPublisher)
 
             const resolvedDDO: DDO = await ocean.resolveDID(ddo.id)
 
             assert(resolvedDDO)
             assert(resolvedDDO.id === ddo.id)
         })
-
     })
 
     describe("#registerAsset()", () => {
-
         it("should register an asset", async () => {
-
-            const metaData: MetaData = new MetaData()
-            const ddo: DDO = await ocean.registerAsset(metaData, testPublisher)
+            const ddo: DDO = await ocean.registerAsset(metadata, testPublisher)
 
             assert(ddo)
             assert(ddo.id.startsWith("did:op:"))
@@ -87,9 +79,7 @@ describe("Ocean", () => {
     })
 
     describe("#searchAssets()", () => {
-
         it("should search for assets", async () => {
-
             const query = {
                 offset: 100,
                 page: 0,
@@ -106,36 +96,30 @@ describe("Ocean", () => {
 
             assert(assets)
         })
-
     })
 
     describe("#searchAssetsByText()", () => {
-
         it("should search for assets", async () => {
             const text = "office"
             const assets: any[] = await ocean.searchAssetsByText(text)
 
             assert(assets)
         })
-
     })
 
     describe("#signServiceAgreement()", () => {
-
         it("should sign an service agreement", async () => {
-
             const publisher = accounts[0]
             const consumer = accounts[1]
 
-            const metaData = new MetaData()
-            const ddo: DDO = await ocean.registerAsset(metaData, publisher)
+            const ddo: DDO = await ocean.registerAsset(metadata, publisher)
 
             const service: Service = ddo.findServiceByType("Access")
 
             // @ts-ignore
             WebServiceConnectorProvider.setConnector(new WebServiceConnectorMock(ddo))
 
-            await consumer.requestTokens(metaData.base.price)
+            await consumer.requestTokens(metadata.base.price)
 
             const signServiceAgreementResult: any = await ocean.signServiceAgreement(ddo.id,
                 service.serviceDefinitionId, consumer)
@@ -146,17 +130,14 @@ describe("Ocean", () => {
             assert(signServiceAgreementResult.serviceAgreementSignature.startsWith("0x"))
             assert(signServiceAgreementResult.serviceAgreementSignature.length === 132)
         })
-
     })
 
     describe("#executeServiceAgreement()", () => {
-
         it("should execute a service agreement", async () => {
-
             const publisher = accounts[0]
             const consumer = accounts[1]
 
-            const ddo: DDO = await ocean.registerAsset(new MetaData(), publisher)
+            const ddo: DDO = await ocean.registerAsset(metadata, publisher)
             const service: Service = ddo.findServiceByType("Access")
 
             // @ts-ignore
@@ -171,6 +152,5 @@ describe("Ocean", () => {
 
             assert(serviceAgreement)
         })
-
     })
 })
diff --git a/test/ocean/ServiceAgreement.test.ts b/test/ocean/ServiceAgreement.test.ts
index 5e86148..37d716a 100644
--- a/test/ocean/ServiceAgreement.test.ts
+++ b/test/ocean/ServiceAgreement.test.ts
@@ -1,9 +1,8 @@
 import {assert} from "chai"
 import ConfigProvider from "../../src/ConfigProvider"
-import Condition from "../../src/ddo/Condition"
-import DDO from "../../src/ddo/DDO"
-import MetaData from "../../src/ddo/MetaData"
-import Service from "../../src/ddo/Service"
+import { Condition } from "../../src/ddo/Condition"
+import { DDO } from "../../src/ddo/DDO"
+import { Service } from "../../src/ddo/Service"
 import Account from "../../src/ocean/Account"
 import DID from "../../src/ocean/DID"
 import IdGenerator from "../../src/ocean/IdGenerator"
@@ -15,6 +14,8 @@ import WebServiceConnectorProvider from "../../src/utils/WebServiceConnectorProv
 import config from "../config"
 import TestContractHandler from "../keeper/TestContractHandler"
 import WebServiceConnectorMock from "../mocks/WebServiceConnector.mock"
+import { metadataMock } from "../testdata/MetaData"
+
 
 let ocean: Ocean
 let accounts: Account[]
@@ -28,6 +29,8 @@ const did: DID = DID.generate()
 
 describe("ServiceAgreement", () => {
 
+    const metadata = metadataMock
+
     before(async () => {
         ConfigProvider.setConfig(config)
         await TestContractHandler.prepareContracts()
@@ -37,7 +40,6 @@ describe("ServiceAgreement", () => {
         publisherAccount = accounts[1]
         consumerAccount = accounts[2]
 
-        const metadata = new MetaData()
         const serviceAgreementTemplate: ServiceAgreementTemplate =
             new ServiceAgreementTemplate(new Access())
 
diff --git a/test/ocean/ServiceAgreementTemplate.test.ts b/test/ocean/ServiceAgreementTemplate.test.ts
index 8a7cc27..0c30b51 100644
--- a/test/ocean/ServiceAgreementTemplate.test.ts
+++ b/test/ocean/ServiceAgreementTemplate.test.ts
@@ -1,6 +1,5 @@
 import {assert} from "chai"
 import ConfigProvider from "../../src/ConfigProvider"
-import MetaData from "../../src/ddo/MetaData"
 import Account from "../../src/ocean/Account"
 import Ocean from "../../src/ocean/Ocean"
 import ServiceAgreementTemplate from "../../src/ocean/ServiceAgreements/ServiceAgreementTemplate"
@@ -9,12 +8,16 @@ import TemplateBase from "../../src/ocean/ServiceAgreements/Templates/TemplateBa
 import config from "../config"
 import TestContractHandler from "../keeper/TestContractHandler"
 import TestIdGenerator from "../TestIdGenerator"
+import { metadataMock } from "../testdata/MetaData"
+
 
 let ocean: Ocean
 let accounts: Account[]
 
 describe("ServiceAgreementTemplate", () => {
 
+    const metadata = metadataMock
+
     before(async () => {
         ConfigProvider.setConfig(config)
         await TestContractHandler.prepareContracts()
@@ -49,7 +52,7 @@ describe("ServiceAgreementTemplate", () => {
                 new ServiceAgreementTemplate(access)
             assert(serviceAgreementTemplate)
 
-            const conds = await serviceAgreementTemplate.getConditions(new MetaData(),
+            const conds = await serviceAgreementTemplate.getConditions(metadata,
                 TestIdGenerator.generatePrefixedId())
             assert(conds)
         })
diff --git a/test/testdata/MetaData.ts b/test/testdata/MetaData.ts
index 1ea7eb0..610889d 100644
--- a/test/testdata/MetaData.ts
+++ b/test/testdata/MetaData.ts
@@ -1,34 +1,57 @@
-import MetaDataModel from "../../src/ddo/MetaData"
-import MetaDataBase from "../../src/ddo/MetaDataBase"
+import { MetaData } from "../../src/ddo/MetaData"
 
-const MetaData = new MetaDataModel({
+export const metadataMock: MetaData = {
     base: {
-        name: "Office Humidity",
+        name: "UK Weather information 2011",
         type: "dataset",
         description: "Weather information of UK including temperature and humidity",
         size: "3.1gb",
-        dateCreated: "2012-02-01T10:55:11+00:00",
+        dateCreated: "2012-10-10T17:00:000Z",
         author: "Met Office",
         license: "CC-BY",
         copyrightHolder: "Met Office",
         encoding: "UTF-8",
         compression: "zip",
         contentType: "text/csv",
-        // tslint:disable-next-line
-        workExample: "stationId,latitude,longitude,datetime,temperature,humidity423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68",
+        workExample: "423432fsd,51.509865,-0.118092,2011-01-01T10:55:11+00:00,7.2,68",
         contentUrls: [
             "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
             "https://testocnfiles.blob.core.windows.net/testfiles/testzkp.zip",
         ],
         links: [
-            {sample1: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-daily/"},
-            {sample2: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-averages-25km/"},
-            {fieldsDescription: "http://data.ceda.ac.uk/badc/ukcp09/"},
+            {
+                // tslint:disable-next-line
+                sample1: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-daily/"
+            },
+            {
+                // tslint:disable-next-line
+                sample2: "http://data.ceda.ac.uk/badc/ukcp09/data/gridded-land-obs/gridded-land-obs-averages-25km/"
+            },
+            {
+                fieldsDescription: "http://data.ceda.ac.uk/badc/ukcp09/",
+            },
         ],
         inLanguage: "en",
         tags: "weather, uk, 2011, temperature, humidity",
         price: 10,
-    } as MetaDataBase,
-} as MetaDataModel)
-
-export default MetaData
+    },
+    curation: {
+        rating: 0.93,
+        numVotes: 123,
+        schema: "Binary Votting",
+    },
+    additionalInformation: {
+        updateFrecuency: "yearly",
+        checksum: "",
+        structuredMarkup: [
+            {
+                uri: "http://skos.um.es/unescothes/C01194/jsonld",
+                mediaType: "application/ld+json",
+            },
+            {
+                uri: "http://skos.um.es/unescothes/C01194/turtle",
+                mediaType: "text/turtle",
+            },
+        ],
+    },
+}