diff --git a/src/ddo/Asset.ts b/src/ddo/Asset.ts
new file mode 100644
index 00000000..fa4deb23
--- /dev/null
+++ b/src/ddo/Asset.ts
@@ -0,0 +1,109 @@
+import { DDO } from './DDO'
+
+export interface AssetNft {
+  /**
+   * Contract address of the deployed ERC721 NFT contract.
+   * @type {string}
+   */
+  address: string
+
+  /**
+   * Name of NFT set in contract.
+   * @type {string}
+   */
+  name: string
+
+  /**
+   * Symbol of NFT set in contract.
+   * @type {string}
+   */
+  symbol: string
+
+  /**
+   * ETH account address of the NFT owner.
+   * @type {string}
+   */
+  owner: string
+
+  /**
+   * State of the asset reflecting the NFT contract value.
+   * 0	Active.
+   * 1	End-of-life.
+   * 2	Deprecated (by another asset).
+   * 3	Revoked by publisher.
+   * 4	Ordering is temporary disabled.
+   * @type {number}
+   */
+  state: 0 | 1 | 2 | 3 | 4
+}
+
+export interface AssetDatatoken {
+  /**
+   * Name of NFT set in contract.
+   * @type {string}
+   */
+  name: string
+
+  /**
+   * Symbol of NFT set in contract.
+   * @type {string}
+   */
+  symbol: string
+
+  /**
+   * Contract address of the deployed ERC20 contract.
+   * @type {string}
+   */
+  address: string
+
+  /**
+   * ID of the service the datatoken is attached to.
+   * @type {string}
+   */
+  serviceId: string
+}
+
+export interface AssetLastEvent {
+  tx: string
+  block: number
+  from: string
+  contract: string
+}
+
+export class Asset extends DDO {
+  /**
+   * Contains information about the ERC721 NFT contract which represents the intellectual property of the publisher.
+   * @type {string}
+   */
+  nft: AssetNft
+
+  /**
+   * Contains information about the ERC20 datatokens attached to asset services.
+   * @type {string}
+   */
+  datatokens: AssetDatatoken[]
+
+  /**
+   * Contains information about the last transaction that created or updated the DDO.
+   * @type {string}
+   */
+  event: AssetLastEvent
+
+  /**
+   * The stats section contains different statistics fields.
+   * @type {string}
+   */
+  stats: { consume: number }
+
+  /**
+   * If asset is listed in purgatory and reason.
+   * @type {string}
+   */
+  isInPurgatory: string
+
+  /**
+   * Name of NFT set in contract.
+   * @type {AssetDatatoken}
+   */
+  dataTokenInfo: AssetDatatoken // To be removed
+}
diff --git a/src/ddo/Metadata.ts b/src/ddo/Metadata.ts
index 90b48326..425592b8 100644
--- a/src/ddo/Metadata.ts
+++ b/src/ddo/Metadata.ts
@@ -1,26 +1,127 @@
 export interface MetadataAlgorithm {
+  /**
+   * Language used to implement the software.
+   * @type {string}
+   */
   language?: string
+
+  /**
+   * Version of the software preferably in SemVer notation.
+   * @type {string}
+   */
   version?: string
+
+  /**
+   * Object describing the Docker container image.
+   * @type {Object}
+   */
   container: {
+    /**
+     * The command to execute, or script to run inside the Docker image.
+     * @type {string}
+     */
     entrypoint: string
+
+    /**
+     * Name of the Docker image.
+     * @type {string}
+     */
     image: string
+
+    /**
+     * Tag of the Docker image.
+     * @type {string}
+     */
     tag: string
+
+    /**
+     * Checksum of the Docker image.
+     * @type {string}
+     */
     checksum: string
   }
 }
 
 export interface Metadata {
+  /**
+   * Contains the date of publishing in ISO Date Time
+   * @type {string}
+   */
   created: string
+
+  /**
+   * Contains the the date of last update in ISO Date Time
+   * @type {string}
+   */
   updated: string
+
+  /**
+   * Descriptive name or title of the asset.
+   * @type {string}
+   */
   name: string
+
+  /**
+   * Details of what the resource is.
+   * @type {string}
+   */
   description: string
+
+  /**
+   * Asset type. Includes "dataset" (e.g. csv file), "algorithm" (e.g. Python script).
+   * Each type needs a different subset of metadata attributes.
+   * @type {'dataset' | 'algorithm'}
+   */
   type: 'dataset' | 'algorithm'
+
+  /**
+   * Name of the entity generating this data (e.g. Tfl, Disney Corp, etc.).
+   * @type {string}
+   */
   author: string
+
+  /**
+   * Short name referencing the license of the asset.
+   * If it’s not specified, the following value will be added: “No License Specified”.
+   * @type {string}
+   */
   license: string
+
+  /**
+   * Mapping of URL strings for data samples, or links to find out more information.
+   * Links may be to either a URL or another asset.
+   * @type {string[]}
+   */
   links?: string[]
+
+  /**
+   * Mapping of URL strings for data samples, or links to find out more information.
+   * Links may be to either a URL or another asset.
+   * @type {string[]}
+   */
   tags?: string[]
+
+  /**
+   * The party holding the legal copyright. Empty by default.
+   * @type {string}
+   */
   copyrightHolder?: string
+
+  /**
+   *The language of the content. Use one of the language codes from the IETF BCP 47 standard
+   * @type {string}
+   */
   contentLanguage?: string
+
+  /**
+   * Information about asset of typealgorithm
+   * @type {MetadataAlgorithm}
+   */
   algorithm?: MetadataAlgorithm
+
+  /**
+   * Stores additional information, this is customizable by publisher
+   * @type {any}
+   */
   additionalInformation?: any
 }
diff --git a/src/ddo/Service.ts b/src/ddo/Service.ts
index 0ba45317..12922209 100644
--- a/src/ddo/Service.ts
+++ b/src/ddo/Service.ts
@@ -1,29 +1,139 @@
 export interface PublisherTrustedAlgorithm {
+  /**
+   * The DID of the algorithm which is trusted by the publisher.
+   * @type {string}
+   */
   did: string
+
+  /**
+   * Hash of algorithm’s files section.
+   * @type {string}
+   */
   filesChecksum: string
+
+  /**
+   * Hash of algorithm’s metadata.algorithm.container section.
+   * @type {string}
+   */
   containerSectionChecksum: string
 }
 
 export interface ServiceComputeOptions {
+  /**
+   * Namespaced used for the compute job.
+   * @type {string}
+   */
   namespace: string
+
+  /**
+   * Maximum number of CPUs allocated for a job
+   * @type {number}
+   */
   cpu?: number
+
+  /**
+   * Maximum number of GPUs allocated for a job
+   * @type {number}
+   */
   gpu?: number
+
+  /**
+   * Type of GPU (if any)
+   * @type {string}
+   */
   gpuType?: string
+
+  /**
+   * Maximum amount of memory allocated for a job.
+   * You can express memory as a plain integer or as a fixed-point number using one of these suffixes: E, P, T, G, M, k.
+   * You can also use the power-of-two equivalents: Ei, Pi, Ti, Gi, Mi, Ki.
+   * For example, the following represent roughly the same value: 128974848, 129e6, 129M, 123Mi
+   * @type {string}
+   */
   memory?: string
+
+  /**
+   * Amount of disk space allocated.
+   * You can express it as a plain integer or as a fixed-point number using one of these suffixes: E, P, T, G, M, k.
+   * You can also use the power-of-two equivalents: Ei, Pi, Ti, Gi, Mi, Ki.
+   * @type {string}
+   */
   volumeSize?: string
+
+  /**
+   * If true, any passed raw text will be allowed to run.
+   * Useful for an algorithm drag & drop use case, but increases risk of data escape through malicious user input.
+   * Should be false by default in all implementations.
+   * @type {boolean}
+   */
   allowRawAlgorithm: boolean
+
+  /**
+   * If true, the algorithm job will have network access.
+   * @type {boolean}
+   */
   allowNetworkAccess: boolean
+
+  /**
+   * If empty, then any published algorithm is allowed.
+   * Otherwise, only published algorithms by some publishers are allowed
+   * @type {string[]}
+   */
   publisherTrustedAlgorithmPublishers: string[]
+
+  /**
+   * If empty, then any published algorithm is allowed. (see below)
+   * @type {PublisherTrustedAlgorithm[]}
+   */
   publisherTrustedAlgorithms: PublisherTrustedAlgorithm[]
 }
 
 export interface Service {
+  /**
+   * Type of service (access, compute, wss.
+   * @type {string}
+   */
   type: 'access' | 'compute' | string
+
+  /**
+   * Encrypted file URLs.
+   * @type {string}
+   */
   files: string
+
+  /**
+   * Datatoken address
+   * @type {string}
+   */
   datatokenAddress: string
+
+  /**
+   * Provider URL (schema + host).
+   * @type {string}
+   */
   serviceEndpoint: string
+
+  /**
+   * Describing how long the service can be used after consumption is initiated.
+   * @type {string}
+   */
   timeout: string
+
+  /**
+   * Service friendly name
+   * @type {string}
+   */
   name?: string
+
+  /**
+   * Service description
+   * @type {string}
+   */
   description?: string
+
+  /**
+   * If service is of typecompute, holds information about the compute-related privacy settings & resources.
+   * @type {string}
+   */
   compute?: ServiceComputeOptions
 }
diff --git a/src/ddo/index.ts b/src/ddo/index.ts
index 4bd3a54b..06eb4fc6 100644
--- a/src/ddo/index.ts
+++ b/src/ddo/index.ts
@@ -1 +1,5 @@
 export * from './DDO'
+export * from './Asset'
+export * from './Service'
+export * from './Credentials'
+export * from './Metadata'