1. Active Databases as Information Systems
Dina Q Goldin
University of Connecticut, USA
with Srinath Srinivasa, IIIT Bangalore, and Vijaya Srikanti, University of Connecticut
IDEAS 2004

2. What are Databases?
Databases: systems that manage a large collection of (static) data
Database instance: a state of the database
Users can perform queries & updates
query: current DB state -> query answer
update: current DB state -> new DB state
Integrity constraints
Specify relations between data values in a DB state
Restrict the set of allowable DB states
Databases disallow updates that violate the constraints
passive approach; something more active is desired
IDEAS 2004

3. Perhaps the problem is that ADBs should not be viewed as DBs?
Active Databases
Database system augmented with rule handling
Active approach to managing integrity constraints
ECA rules: event, condition, action
Many other uses have been found for active rules
Maintaining materialized views
Managing derived data
Coordinating distributed data management
Providing transaction models
Etc.
Provably correct universal solutions lacking…
Specifying rules
Rules analysis (termination, confluence, observable determinism)
Perhaps the problem is that ADBs should not be viewed as DBs?
IDEAS 2004

4. Talk Overview From Databases to Active Databases
Database Systems vs. Information Systems
The Two Views of Active Databases
as database systems
as information systems
Why switch?
IDEAS 2004

5. Information System = Database + Interaction [GST00]
DBs vs. IS’s
state
user data
user data, logs and histories, user profiles
job
updates & queries of data
data-backed services to users
output
determined completely by query/update specification
individualized based on user history & preferences
integrity concerns
static integrity (of a DB state), maintained passively
static & dynamic integrity (of IS behavior), maintained actively
nature
static, algorithmic data transformation engine
dynamic, interactive service providing system
Information System = Database + Interaction [GST00]
IDEAS 2004

6. Example: Integrity Constraints
Static (Data) Integrity
Express conditions for single database states
Can be specified in first-order logic
Dynamic (Interactive) Integrity
- Constraints on state sequences
- Express conditions for traversal of state space of the system (i.e. its behavior).
- Traversal may involve interaction with user(s).
DBs support only static integrity constraints.
IDEAS 2004

7. DBs support only atomic user operations.
Example: Operations
Operations
Logical unit of dynamics
Services in IS, transactions in DB
IS service: a semantic process that usually involves interaction with one or more external agents (users, other services)
Three types: user, system, prompted
User operations
- Initiated by the user (CMS example: submitting a paper).
- System cannot predict when it is initiated, nor its trajectory.
System operations
Initiated and carried out by the system (ex: deleting expired member).
Internal to the system; user does not control, may be unaware.
Prompted operations
Initiated by the system, involve interaction with the user (CMS example: assign reviewer to paper after it’s submitted).
DBs support only atomic user operations.
IDEAS 2004

8. The Principles of the Two Fields
We have provided a working distinction for the purpose of discussing the “principles” of each field
Borders between DBs and ISs are blurred:
Database Systems provide a data management service to users (can be viewed as a simple information system)
Data-Intensive Information Systems perform data management
Active DBs fall within that blurry area
a DB augmented with active rule handling (to perform system operations)
a data-intensive IS restricted to rule-handling services
IDEAS 2004

9. Two Views of Active Databases as Databases with Rules as specialized IS
state
user data
user data, rule-related logs & histories, rule-related user profiles
job
updates & queries of data, by user as well as rule-driven
data-backed rule-based services to users
output
determined completely by query/update specification
individualized based on user history & preferences
integrity concerns
static integrity, maintained actively via rules
static & dynamic integrity, maintained actively
nature
static, algorithmic data transformation engine
dynamic, interactive service providing system
The traditional DB view is more limiting, does not allow ADBs to achieve their full potential.
IDEAS 2004

10. Talk Overview From Databases to Active Databases
Database Systems vs. Information Systems
The Two Views of Active Databases
as database systems
as information systems
Why switch?
Active views example
ADB wish list
IDEAS 2004

11. ADBs as Information Systems
The IS view naturally endows ADBs with needed functionality
Individualization: customization of requests, as well as of feedback viewing
Use of logs and profiles
User interaction
Interaction among rules
Dynamic integrity
Example: active views
IDEAS 2004

12. Active Views Active Views DB view of active views
Mediate between ADB users and data
Automate user monitoring of certain events or condition
Provide subscription services and notification services
DB view of active views
- Compile user specifications into active rules.
- Provide active caching of materialized views.
IS view of active views
Provide individualized services to ADB users: event monitoring, subscription and notification.
A more natural approach
IDEAS 2004

13. ADB Wish List Rule instances Rule history Rule interaction
Support multiple instances of the same rule
Now possible only when the condition part of their ECA structure differs.
Can be directly mapped to different instances of IS services.
Rule history
Store the history of events, conditions, actions for each rule instance.
To help transactions handle dynamic integrity violations during rule execution.
Rule interaction
Allow rules to enable, disable, or wait for other rules.
As separate functionality rather than by extending the condition part of ECA structure.
Rules need not be aware of external control over their behavior.
For easier formulization of synchronization across semantic services.
IDEAS 2004