Technologies for PubSub Application Format (PSAF )

Technologies for PubSub Application

Format (PSAF)Leonardo Chiariglione CEDEO.net

Kenichi Nakamura (Panasonic)Giuseppe Tropea (CNIT)Valencia, ES, 2014/04/01

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Publish/Subscribe (PubSub)

An established communication paradigm where communication is Not directly between Sender and Receiver butMediated by a service between Sender and Receiver

How it worksSenders (called Publishers) post information on their

information to a service Receivers (called Subscribers) declare their interest

in a certain type of information to the same service The match service detects Pub/Sub matches and

notifies accordingly

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PubSub actors and workflow

Creator stores content

Publisher publishes information on content

Subscriber subscribes to a type of content

Match Service Matches subscription with publication Issues appropriate notification(s)

Consumer plays content referenced in notification

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Information exchange in PubSub

Step Information typeCreator stores resource Resource IDCreator stores info on resource

Resource format (RI)

Publisher publishes info on resource

Publication format (PI)

Subscriber subscribes to resources of his interest

Subscription format (SI)

Service matches sub with pubs

No requirement

Service issues notification(s) Notification format (NI)

Subscriber opens notification, requests/plays resource

No requirement 4

Information Centric Networking (ICN)

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In ICN, entities are individual, identifiable (named) content elements, instead of unidentifiable data containers (i.e., IP packets)

Give me today’s issue of Time Magazine

Connect me with host 66.45.78.89

Current Address Centric Networking

Future InformationCentric Networking

PubSub is well suited for ICN

PubSub users shall be able to/1

1. Define lists of users to be/not to be notified of an event EnumerationsGroups of users Users satisfying certain conditions

2. Reference the Resource via a standard information package containingDescriptions of ResourceRights and conditions for use of ResourceList of users to be notified that specific use of a

Resource has been made

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3. Select Match Service Provider(s)

4. Prescribe to Match Service Provider ;ist ofPub-Sub users to be considered in computing

matches, specifically defined as Subscriptions to be/not to be considered as

candidates for matches with publicationsPublishers to be/not to be considered as candidates

for matches with subscribersUsers to be/not to be notified of an event in the

event of a match

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5. Define additional conditions to be added to Publications and Subscriptions such as Validity of Publication/Subscription (i.e. the

period of time defined by a start and end time the Match Service Provider shall notify matches)

6. Update their Publications/Subscriptions

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Elements of Resource Information

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Resource Name the RI refers toMetadata for the purpose of Resource useID of user who creates RIRights to use Resource that include Principal ID(s) Resource Locator/Address/Name the Rights

refer to Rights to use Conditions to useID of users to be notified that Resource has been used ID of Resource InformationSignature of user who creates RI

Elements of Publication Information

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ID of RI this PI refers toMetadata for the purpose of Resource publicationID of PublisherRights to match Publication Metadata including Match Service ID(s) ID of this PI Right to match, for how long Subject to condition that Subscriptions

come/do not come from specific UsersID of users who shall be notified of a matchID of users who shall not be notified of a match foundID of PIPublisher’s Signature

Elements of Subscription Information

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QueryID of SubscriberRights to match Query that includes Match Service ID(s) ID of this SI Right to match, for how long Subject to condition that Publications

come/do not come from specific User ID(s)ID of users who shall be notified of a matchID of users who shall not be notified of a matchID of SISubscriber’s Signature

Elements of Notification Information

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ID of RIID of PIID of SIID of NotifierID of NIMatch Service Provider’s Signature

Match Service

Peer2

Peer1

RI

PI

SI

SI PI

NI

RI

Content Centric NetworkRI

MATCH

RequestRI

StoreRI

PublishPI

SubscribeSI

NI

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2

3 4

5

6

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Publish/Subscribe in ICN

Technologies for PSAFMPEG technologies to specify the PSAF

Digital ItemDigital Item IdentifierSimple Metadata ProfileMPEG Query FormatRights Expression Language Event Reporting

Outside MPEG to specify the PSAFW3C Signature Recommendation.

2012/09/13 14A gateway to new opportunities for digital content

Design of RI, PI, SI, NI/1INFORMATION OBJECT

HEADERPAYLOADRIGHTSNOTIFICATION

HEADER INFORMATION OBJECT IDSIGNATURE of INFORMATION OBJECT’s creator


Design of RI, PI, SI, NI/2PAYLOAD

TYPE of payload (R, P, S, N)USER ID of INFORMATION OBJECT’s creatorMETADATA {optional, for instance in case of NI}

[ RESOURCE METADATA ] or [ PUB METADATA ] or [ SUB METADATA ] RESOURCE METADATA

[ KEYWORDS ] or [ FIELD-VALUE ] or [ STRUCTURED DATA ] PUB METADATA

[ KEYWORDS ] or [ FIELD-VALUE ] or [ STRUCTURED DATA ] SUB METADATA

QUERY

List of IDs of INFORMATION OBJECTs the PAYLOAD refers to {optional, e.g. in case of SI}

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Design of RI, PI, SI, NI/3RIGHT

PRINCIPALsList of USER/SERVICE IDENTIFIERS

VERBs ID of INFORMATION OBJECT the RIGHT refers toCONDITIONs

[ List of USERs who must be involved in the RIGHT ] or [ other REL conditions ]

NOTIFICATIONRECIPIENTs to notify

List of USER IDs to notifyList of USER IDs not to notify

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Discussion – PAYLOAD/1KEYWORD and FIELD-VALUE to cover most PubSub

Applications’ needs for

STRUCTURED DATA element imported by the didl-msx schema to define any kind of XML based metadata (including RDF/XML) - when metadata in the form of field/value is not sufficient

QUERY element imported from the MPEG Query Format schema (e.g. of InputQueryType). The MPQF schema can contain any kind of queries, as it can flexibility define complex disjunctive/conjunctive queries of any type e.g. SPARQL, XQuery, or field/value.

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Discussion – PAYLOAD/2Identifier of user/peer that created the Information

object – needed to serve as conditions (in the RIGHT block of matching objects) to filter the match based on information issuer.

Identifiers the payload refers to – a vital information to be reported back to users: for instance In NI the triple {ID of PI, ID of SI, ID of RI} is reported

back to a subscriber to signal that the specific SI issued by the subscriber matches a specific PI and the relevant resource can be located through the given RI


Discussion – RIGHT/1Requires a verb to indicate the right to perform

MATCH of a pub with a sub and vice-versa. Current REL specification does not appear to include such a verb.

Need to specify conditions, to restrict MATCH to Information objects coming from selected issuers or to notify only of matches that satisfy the given conditions.

We want to have the right to match a pub with a sub to be subject to the fact that a “third party shares in the execution of the right”, in addition to the right’s principal


Discussion – RIGHT/2A new verb NOTIFY is a possible alternative, i.e.

he right to create a list of users/peers to be notified depending on the result of satisfying the conditions expressed inPublications

Users to be/not to be notifiedSubscriptions that are eligible for matches with

PublicationsSubscriptions

Users to be/not to be notifiedPublications that are eligible for matches with

Subscriptions


Discussion – RIGHT/3An alternative is the use of CEL.

In REL “Pub-Sub user gives MSP the right to match” and MSP has the duty to notify

In CEL more sophisticated Pub-Sub user vs Match Service Provider relationships can be encodedPublisher will pay 20 € if MSP notifies 1000 (Mil) Subscribers

as profiled in Publication, satisfying Subscribers’ conditions. The Cost Per Mil (CPM) notifications could depend on how

finely the Publication profiles Subscribers.

With User Description Publishers (Subscribers) can make fine specification of target Subscribers (Publisers) because Pub-Sub users share the semantics of user descriptors.

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Discussion - NOTIFICATIONWhenever a match occurs between a specific PI

and SI, the notification lists of PI and SI are crosschecked to preserve the request made by Pub-Sub users for dissemination of notifications If user A is on the black list of the SI (i.e. SI’s

creator B didn’t want user A to be notified whenever B’s SI gets matched), but also on the white list of the PI, user A will not be notified.

The white list may include the creator of the Information object but, if that user appears on the black list of the matching Information, the original creator is not notified.

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Mapping to existing technologies


PSAF Element

Existing Technology

Notes

HEADER DI and DII (and W3C Signature)

Fully covered

PAYLOAD DI, DII, MPQF, Simple Metadata Profile

Application specific and main subject of this specification

RIGHT REL, ER Well covered with exceptions relative to new verb and conditions

Schema of PSAF Payload/1

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<xsd:schema> <xsd:element name="PSAFPayload" type="PSAFPayloadType" /><xsd:element name="ResourceMetadata" type="ResourceMetadataType" /><xsd:element name="PublicationMetadata" type="PublicationMetadataType" /><xsd:element name="SubscriptionMetadata" type="SubscriptionMetadataType" /><xsd:element name="FieldValue" type="FieldValueType" /> <xsd:complexType name="PSAFPayloadType"><xsd:sequence><xsd:element name="InformationObjectType" type="xsd:string" /><xsd:element name="InformationObjectCreator" type="xsd:anyURI" /><xsd:choice minOccurs="0"><xsd:element name="ResourceMetadata" type="ResourceMetadataType" /><xsd:element name="PublicationMetadata" type="PublicationMetadataType" /><xsd:element name="SubscriptionMetadata" type="SubscriptionMetadataType" /></xsd:choice><xsd:element name="InformationObjectIdentifier" type="xsd:anyURI" minOccurs="0" maxOccurs="unbounded"/></xsd:sequence></xsd:complexType>


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<xsd:complexType name="ResourceMetadataType"><xsd:sequence><xsd:element name="Keyword" type="xsd:string" minOccurs="0" maxOccurs="unbounded"/><xsd:element name="FieldValue" type="FieldValueType" minOccurs="0" maxOccurs="unbounded"/><xsd:element name="StructuredData" type="didl-msx:StructuredDataType" minOccurs="0" maxOccurs="unbounded"/></xsd:sequence></xsd:complexType> <xsd:complexType name="PublicationMetadataType"><xsd:sequence><xsd:element name="Keyword" type="xsd:string" minOccurs="0" maxOccurs="unbounded"/><xsd:element name="FieldValue" type="FieldValueType" minOccurs="0" maxOccurs="unbounded"/><xsd:element name="StructuredData" type="didl-msx:StructuredDataType" minOccurs="0" maxOccurs="unbounded"/></xsd:sequence></xsd:complexType>


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<xsd:complexType name="SubscriptionMetadataType"><xsd:sequence><xsd:element name="Query" type="mpqf:InputQueryType"/></xsd:sequence></xsd:complexType> <xsd:complexType name="FieldValueType"><xsd:sequence><xsd:element name="Field" type="xsd:string"/><xsd:element name="Value" type="xsd:anySimpleType"/></xsd:sequence></xsd:complexType> </xsd:schema>

ConclusionsThis document proposes

Multimedia application requirements in PubSub messaging that take into account controlled distribution of information

Four payload formatsA set of (MPEG) technologies that can be used to

specify the formats

There are some alternatives that may need further investigations but there is enough material to start drafting the PSAF standard

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Documents

Technologies for PubSub Application Format (PSAF )