Service Oriented Architecture (SOA) and Complex Event Processing (CEP) – Complementary Views of the Enterprise John Salasin, Ph. D. Defense Advanced Research Projects Agency (DARPA)

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

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.