Personal Activity Coordinator

Shelley ZhuangComputer Science Division

U.C. Berkeley

Ericsson WorkshopAugust 2000

PAC: What is it?

• Service coordination layer• Collects contextual user information such as

current geo-location, next destination from services such as GPS service, calendar service, IM-Anywhere (real-time presence, location, and behavior information)

• Spatial data (location, traffic, device type, etc)• Temporal data (calendar data)

Goals

• Uncoupling of providers and consumers• Extensibility• High availability and fault tolerance• Scalability• Security• Privacy

PAC Applications

• Real-time information about PAC users, enabling targeted message delivery and other enhanced services

• Assists the Preference Registry for more powerful service customization

Contextual Information Categorization

• Categorizing contextual information – information updating performance vs. finer grained access control)

• Hierarchical name space• Sample hierarchical categorization tree

root

new appointments trafficlocation calendar

fax email trip timeGPS IP address mailing address location person

Schema Definition

• XML namespace standard• Referenced by a well-known URL• Single schema definition file for each

contextual information category• Defines the properties of each field of a

contextual information category• Tags associated with each field are: Name,

Description, Type, Enforcement, Values

Hierarchical Domain-based PAC Organization

• Separate PAC is provided for each individual user: ease of maintainability, privacy

• Individual PACs are organized in a hierarchical domain-based fashion

• Uniform contextual information presentation defined for each domain of PACs– Child domains inherit the presentations

defined by their parents– Supports dynamic creation and deletion of a

category, creation of additional fields for a category, and update of schema definition file URL at the domain level

Internal View of the PAC

• Hierarchical category namespace defined by the domain, and schema definition files

• Contextual information repository• Subscriber Information

– Service consumers subscribe to contextual information categories

– Notified in response to the creation, deletion, update and expiration of contextual information

Architecture of PAC

root

Hierarchical Name Space

name Server

name Servername Server

subscriber 5

subscriber 6

subscriber 7

subscriber server

Subscribers Space

subscriber 1

subscriber 2

subscriber 3

subscriber 4

subscriber server

subscriber server

Subscribers Space

node server

node server node server

node server

virtual node server

node server

node server node server

node server

virtual node server

Contextual Information RepositoryLight-weight semi-structured distributed database

Security & Privacy

• Public key infrastructure• For each contextual information category, the

user can specify an Access Control List (ACL)

Garbage Collector

• Contextual information stored as soft state• Allow the service providers to specify the

lasting period of a contextual information

Execution Environment

• Runs on a Ninja base (iSpace vSpace)• Name Lookup Service (service-specific-id

user’s unique-id personal information, i.e., preference registry, public key, PAC

• Xset database – XML based database and query model

Future Work

• Migrate to Ninja vSpace• Implement the security model• Support query-based notifications for finer

grained control of the notification scheme• Real-time changing data - GPS, IM-Anywhere• User’s current activity – identify categorization

and semantics