Service Oriented Architecture (SOA) and Complex Event

Processing (CEP) – Complementary Views of the

Enterprise

John Salasin, Ph. D.Defense Advanced Research Projects

Agency (DARPA)John.Salasin@darpa.mil, jsalasin@verizon.net

Agenda

• Objectives• Reputed SOA Benefits• Conceptual view of an SOA-based system• Conceptual architecture of an SOA-based

system• Reputed CEP Benefits• Conceptual view of a CEP system • Conceptual CEP Architecture• Generalized Event Processing Agent

Objectives

To provide:

Technical background to justify discussions of similarities and differences;

More on CEP than SOA (less familiar)

Guidance on the contexts in which the techniques are most useful, and;

References to additional information.

Reputed SOA Benefits

Core Concept: “Orchestrating” business functions to provide services.

• Reducing integration expense;

• Increasing asset reuse;

• Increasing business agility, and;

• Reducing business risk.

Conceptual view of an SOA-based system

Conceptual architecture of an SOA-based system

Reputed CEP Benefits

Core concept: specifying and managing conceptual hierarchies, or patterns, of events.

Users receive information at the appropriate semantic level (Aggregation);

Flexibility in monitoring (run-time specification);

Analysis of event patterns (pattern matching against observed patterns or rules/policies), and;

Consolidation (correlation across hierarchic levels).

Conceptual view of a CEP system

NOTE: This has been used to diagram both SOA and CEP.

Conceptual CEP Architecture

Out Actions

ErrorFiltered StringOutput pattern/sequenceConstraint check results

In ActionsFor EPA types:Instantiate, StopInput string (to filter)Input pattern(s) (to map)Input pattern(s) (to check)

Event Processing Agent

Behaviors

Reactive rules to start, terminateB(…) => Pass;A(…), B(…), C(…) => generate Seq (…);B(…) -> A(…) => generate Alert1(…);

//create alert whenever a B causes an A

Generalized Event Processing Agent

CEP Illustrative Examples (1 of 2)

• Pattern matching and analysis – Match what is actually happening (e.g., a broker

“trading ahead” of placing a customer order large enough to change the price of a stock) with pre-defined constraints (e.g. trading ahead is illegal).

• Causal Tracking– Identify the Partially Ordered Set (POSET) of events –

at all levels -- related to a specific event of interest (e.g., failure of a machine on a chip fab line)

– Assure that a sequence of events is correct with respect to policy in complex contexts involving multiparty transactions.

CEP Illustrative Examples (2 of 2)Loan Processing Example -- Causality and

Aggregation

When CEP Is Useful (1 of 2)

SOA is satisfactory when application is data dependent – where the major concerns are with, e.g.:

–The magnitude of variables rather than the time at which they are set;–Relationships among these magnitudes (e.g., sales / ft3 at a set of stores), and;–Triggers are based on magnitude (e.g., order when stock level =< “H”).

When CEP Is Useful (2 of 2)

CEP should be added when concern is with patterns of events in real-time. E.G., We:• Know (or suspect) the pattern of events we’re looking for (e.g., trading ahead);

• Can filter out a finite set of events from the “cloud” to start the process (e.g., sequences starting with customer requests for a stock trade), or;

• Want to respond to the pattern immediately, without the delay in retrospective data searches to see if it occurred.

Potential Added Value of Combining SOA/CEP

CEP at Enterprise level could support data marshaling in complex processes

– Optimize access sequences to allow greatest number (possibly weighted by process priorities or deadlines) of processes to continue.

– Allow identification of causality or dependency relationships across independent services.