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October 18, 2003 Behavioral Signatures and E-Service Composition 1 E-Service Composition and Behavioral Signatures > Rick Hull Bell Labs Research October.

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Presentation on theme: "October 18, 2003 Behavioral Signatures and E-Service Composition 1 E-Service Composition and Behavioral Signatures > Rick Hull Bell Labs Research October."— Presentation transcript:

1 October 18, 2003 Behavioral Signatures and E-Service Composition 1 E-Service Composition and Behavioral Signatures > Rick Hull Bell Labs Research October 18, 2003 slides will be available at Michael Benedikt (Bell Labs) Vassilis Christophides (FORTH, Greece) Jianwen Su (UC Santa Barbara) Based in part on the PODS 2003 talk entitled E-Services: A Look Behind the Curtain, co-authored with

2 October 18, 2003 Behavioral Signatures and E-Service Composition 2 The E-Services Paradigm Goal: Simplify and/or automate e-service – Discovery – Composition – Orchestration (invoke, monitor; choreography) – Provenance (e-science, recovery) Primary roots of e-services paradigm (a) Process description formalisms (b) Distributed computing middleware (c) Data management What makes e-services new – Much more de-centralized than workflow – More flexible, less structured than CORBA – Data management has larger role in (a) and (b) – Importance of standards to enable interoperation and analysis Our focus: how to build, analyze

3 October 18, 2003 Behavioral Signatures and E-Service Composition 3 Outline Events, messaging, and sequential behavior are facts of life – We need a notion of behavioral signature An automata-based framework – Inspired by CSPs, -calculus, verification theory Analysis tools – Several approaches available Automated composition – Including a bridge to DLs Conclusions

4 October 18, 2003 Behavioral Signatures and E-Service Composition 4 Web Services Definition Language (WSDL): Messages and (traditional) I/O signatures Peer-to-peer: e-service can act as client or server – Proactive : send request send request, block till response – Reactive : receive request receive request, send response order receipt bill payment order receipt bill_payment out: bill in: payment Port: mechanism to cluster operations – Port as unit of interoperation between services Supplier

5 October 18, 2003 Behavioral Signatures and E-Service Composition 5 E-Commerce: Patterns of Messages order 1 ok receipt 1 bill 1 payment 1 authorize get buy Certain patterns acceptable, others not Enactments with different life-cycles – E.g., one credit authorize for many order s store bank supplier1 order 2 receipt 2 bill 2 payment 2 Add new services dynamically – Does supplier2 fit? (what if supplier2 uses prepay) supplier2

6 October 18, 2003 Behavioral Signatures and E-Service Composition 6 Using order to infer IOPA properties Conditions on input/output – if valid client sends order, then bill is created – if payment is received, then receipt is sent Conditions on state of world – Amount of $$ in line of credit – Supplier ships order when payment is received Performing inference (everything else fixed) – Assume the Bank satisfies: if bill received and sufficient funds, then payment is sent – Infer that: an order from a valid client with sufficient funds will result in a receipt and shipment of the order order receipt bill payment Supplier

7 October 18, 2003 Behavioral Signatures and E-Service Composition 7 Services use events Full plane reservation service includes alerts if plane is delayed – To person flying – To car rental service, to hotel service, … Services may have to retain context over a period of time – Will be waiting for incoming event – Put it into proper context – Take appropriate actions BPEL4WS has explicit constructs for asynchronous events – receive, wait, pick

8 October 18, 2003 Behavioral Signatures and E-Service Composition 8 Telecom/Collaborative Services Emerging standards will enable flexible, dynamic invocation of services & incorporation of features – Can be viewed as a special case of web services – Bearer traffic vs. signaling/control traffic Asynchronous events: call dropped, person becomes present, … Feature interactions: call screening, call waiting, … Profile Data Presence Server Media Server (voice) Media Server (video) Pre-Pay Session Coordinator

9 October 18, 2003 Behavioral Signatures and E-Service Composition 9 Outline Sequential behavior and messaging are a fact of life – We need a notion of behavioral signature An automata-based framework – Uses a black-box perspective – Contrast to white-box formalisms Some tools are available – Including a bridge to DLs Conclusions

10 October 18, 2003 Behavioral Signatures and E-Service Composition 10 Two perspectives on E-Services Black box: Signature languages – Web Services Description Language (WSDL) Focus on input/output signatures only – Pre-/post conditions á la OWL-S – Behavioral: Focus on sequencing of messages transmitted –W3C Choreography group working here Focus on sequencing of actions performed White box: Implementation languages – Essence of WSFL, XLANG, BPEL4WS*, BPML, etc. standards – OWL-S process constructs – Typically, parallel flowcharts with synchronization, scopes, some event handling, internal variables *BPEL4WS also supports a black box view of e-services

11 October 18, 2003 Behavioral Signatures and E-Service Composition 11 Modeling I: Individual E-services In the most general case, an e-service can be a Turing machine For analysis, optimization, and automation it is useful to study more restricted models input messages to other e-services Do until halt nondeterministic choice: read an input; send an output to some other peer; halt; end choice local store message log

12 October 18, 2003 Behavioral Signatures and E-Service Composition 12 Behavioral signatures using messages Can model single or sequenced enactments Advantages for analysis, e.g., verifying temporal properties, characterizing global behavior ?o?o !r!r !b!b ?p?p ?p?p !r!r !r!r !b!b order rcpt bill pymnt order rcpt bill pymnt !b?p!r ?o?o (a) cautious supplier (b) trusting supplier Use Mealy Peers: Finite State Automata with input/output – Follows spirit of process algebras, communicating processes

13 October 18, 2003 Behavioral Signatures and E-Service Composition 13 Modeling II: A composition framework A peer: autonomous process executing an e-service Assume reliable communication Peer 1 Peer 2... Peer n

14 October 18, 2003 Behavioral Signatures and E-Service Composition 14 C : finite set of peer- to-peer channels An E-C schema is a triple (P, C, M) Specifies the infrastructure of composition E-Composition Schema authorize M : (finite) set of message classes okok bill 2 payment 2 order 1 receipt 1 order 2 receipt 2 payment 1 bill 1 P : finite set of peers (e-services) store bank supplier1 supplier2 Many variations on this base model possible, e.g., – Different levels of granularities – Assume finite domains can model parameters explicitly

15 October 18, 2003 Behavioral Signatures and E-Service Composition 15 Combining Peer and Composition Models Peer fsas begin in their start states... store supplier1 supplier2... bank !o1!o1 !a!a ?k?k !o2!o2 ?b1?b1 ?a?a !k!k ?o1?o1 !b1!b1 ?o2?o2 ?r2?r2 !b2!b2

16 October 18, 2003 Behavioral Signatures and E-Service Composition 16 a Executing a Mealy Composition (cont.)... store supplier1 supplier2... bank STORE produces letter a and sends to BANK !o1!o1 !a!a ?k?k !o2!o2 ?b1?b1 ?a?a !k!k ?o1?o1 !b1!b1 ?o2?o2 ?r2?r2 !b2!b2

17 October 18, 2003 Behavioral Signatures and E-Service Composition 17 Executing a Mealy Composition (cont.) BANK consumes letter a Execution successful if all queues are empty and fsas in final state... store supplier1 supplier2... bank !o1!o1 !a!a ?k?k !o2!o2 ?b1?b1 ?a?a !k!k ?o1?o1 !b1!b1 ?o2?o2 ?r2?r2 !b2!b2

18 October 18, 2003 Behavioral Signatures and E-Service Composition 18 State and Conversation The state of the composition is based on – state of each peer – contents of the queues Conversation : one enactment of global process – Can have sub-conversations of a conversation – Little known about formal properties of conversations r2r2 r2r2 b1b1 b2b2 o1o1... !o1!o1 !a!a ?k?k !o2!o2 ?o2?o2 ?r2?r2 !b2!b2 ?o1?o1 !b1!b1 store supplier1 supplier2... bank o2o2 o2o2 ?b1?b1 ?a?a !k!k

19 October 18, 2003 Behavioral Signatures and E-Service Composition 19 Important Choices for Message-based Composition Model Representation formalism for peer implementations Expressive power of peer implementations Bounded vs unbounded queues Several queues vs one queue vs heap vs … Open vs closed Restricted topologies/control: peer-to-peer, hub-and-spoke, hierarchical, … Show full language or subset Peer 1 Peer 2... Peer n

20 October 18, 2003 Behavioral Signatures and E-Service Composition 20 Composition Infrastructure Peer-to-peer (distributed control) BPEL4WS, BPML, GSFL useful to define mediators Composition of compositions hierarchy... order 1 okok receipt 1 order 2 receipt 2 bill 2 payment 2 bill 1 payment 1 authorize store bank supplier1 supplier2 Hub-and-spoke (centralized control) a k r o b2b2 p2p2 r2r2 o2o2 r1r1 o1o1 b1b1 p1p1 k a b p store supplier1 supplier2 bank mediator

21 October 18, 2003 Behavioral Signatures and E-Service Composition 21 BPEL4WS: Example white-box language Flowcharts with parallelism Pick construct to enable waiting for input (or time out) Synchronization within parallel threads Comparison of supported constructs: see [van der Aalst 03] Initialize pick end_date reached flag := true receive order case suppl1 order suppl2 order end case begin parallel send Order receive Receipt1 send Receipt Receive Bill1 Send Bill Receive Payment Send Payment1 end parallel do until flag

22 October 18, 2003 Behavioral Signatures and E-Service Composition 22 OWL-S Process Model Process class – Atomic, composite (mediator), or simple (virtual) – Inputs, outputs, effects – Pre-conditions, post-conditions Constructs for composite processes – Sequence – Concurrency: Split; Split+Join; Unordered – Choice – If-Then-Else – Looping: Repeat-Until; Iterate (non-deterministic) Data Flow – No explicit variables, no internal data store, no wait – Predicate sameValues to match input of composite service and input of subordinate service Less refined than, e.g., BPEL4WS

23 October 18, 2003 Behavioral Signatures and E-Service Composition 23 Outline Events, messages, and sequential behavior are facts of life An automata-based framework Analysis tools – Petri nets – Tools using temporal logics – Bounded vs. unbounded queues Automatic composition Conclusions

24 October 18, 2003 Behavioral Signatures and E-Service Composition 24 Verifying Properties of DAML-S Processes via Petri nets [Narayanan+McIlraith 02] Specify a DAML-S semantics using a situation calculus – Includes Knows, Kwhether, Kref for condition testing – Captures completion assumptions: essentially prevents world from changing without e-service knowing about it Operational semantics via Petri nets – Assume finite domains – Map to 1-safe Petri nets, which corresponds to bounded queue case Verify properties such as reachability, termination Complexity depends on constructs and model – Range from PTIME to EXPSPACE-hard

25 October 18, 2003 Behavioral Signatures and E-Service Composition 25 Verifying Temporal Properties of Mealy Compositions Label states with propositions – Level of indirection between states and observables Express temporal formulas, e.g., – shipment just made only after line-of-credit avail... store warehouse1 warehouse2... bank !o1!o1 !a!a ?k?k !o2!o2 ?b1?b1 ?a?a !k!k ?o1?o1 !b1!b1 ?o2?o2 ?r2?r2 !b2!b2 ?r2?r2 !b2!b2 line-of- credit available shipment just made shipment just made

26 October 18, 2003 Behavioral Signatures and E-Service Composition 26 Results on Temporal Verification Long history, e.g., [Clarke et.al. 00] E.g., verification for fsas and propositional LTL – Complexity: PSPACE in size of formula + fsa linear time in size of fsa Application to Mealy compositions – Results apply to open and closed case – Bounded queues Composition can be simulated as Mealy machine Verification is decidable Standard techniques to reduce cost – Unbounded queues In general, undecidable Approximation techniques can be applied

27 October 18, 2003 Behavioral Signatures and E-Service Composition 27 Qualitative Analysis of Unbounded Queue Compositions Conversation Languages [Bultan et.al. WWW03] Assume a watcher that observes all messages sent – In contrast to previous approach, the observables here are simply the messages sent Language of peer implementation is set of words formed by successful executions of the implementation Peer 1 Peer 2... Peer n ako1o1 b1b1 o2o2 p1p1... Watcher

28 October 18, 2003 Behavioral Signatures and E-Service Composition 28 Example Conversation Language Language: ak SH( (o 1 r 1 b 1 p 1 )*, (o 2 SH(r 2,b 2 p 2 ))* ) – First ak, then a shuffle of orders against Supplier1 and orders against Supplier2 – Supplier1 is cautious and Supplier2 is trusting This language is regular Same language for bounded or unbounded queues... store supplier1 supplier2... bank !o1!o1 !a!a ?k?k !o2!o2 ?b1?b1 ?a?a !k!k ?o1?o1 !b1!b1 ?o2?o2 ?r2?r2 !b2!b2

29 October 18, 2003 Behavioral Signatures and E-Service Composition 29 (a) Store (b) Supplier (c) Bank Unbounded Queues Unexpected Behaviors Abstract versions of previous e-services – But, no handshakes for messages Conversation language L: – L ao*b* = { ao n b n | n 0 }, i.e., L is not regular Take aways: – Bottom up design of compositions may lead to undesirable global behaviors – Service mediators can have important role in preventing undesirable behaviors !b ?o ?b ?a !o !a

30 October 18, 2003 Behavioral Signatures and E-Service Composition 30 How bad is it ? In general, conversation language with Mealy peers and unbounded queues is context-sensitive – Accepted by a quasi-realtime automaton with 3 queues All conversation languages are closed under two key properties – Join: if w is generated, then certain shuffle products of w are also generated – Prepone: interchange order of input and output messages of a peer p under certain conditions For hierarchical ec-schemas: Each peer is a Mealy implementation Conversation language is join-prepone closure of a regular language

31 October 18, 2003 Behavioral Signatures and E-Service Composition 31 Outline Events, messaging, and sequential behavior are facts of life An automata-based framework Analysis tools Automatic composition – Hierarchical composition – Results from DAML-S community – Results using Mealy machines – A bridge to DLs Conclusions

32 October 18, 2003 Behavioral Signatures and E-Service Composition 32 Hierarchical Composition A pragmatic approach to automating e-service composition Travel Service Templates Air Travel Templates Airport Transfer Hotel Reservation Customized Travel Service

33 October 18, 2003 Behavioral Signatures and E-Service Composition 33 Hierarchical Composition (cont.) Approach: – Assume a library of e-service templates and ground specs – Based on input criteria select a root template, then fill in gaps with other templates and/or ground specs – [Christophides et.al. 01b] does this for structured workflows Take-away: Hierarchical structuring is important for e-service formalisms – Need to incorporate this into OWL-S, Mealy model

34 October 18, 2003 Behavioral Signatures and E-Service Composition 34 Automatic Composition for DAML-S [Narayanan+McIlraith 02]: Search over all combinations Recall simulation of DAML-S via 1-safe Petri nets 1.For set of atomic e-services, create Petri Net that represents all possible combinations of them 2.Specify desired goal as a state of this Petri Net 3.Determine if this goal state is reachable In this framework reachability is PSPACE- complete in size of Petri net – Petri net itself may be exponential in size of atomic e-services – Heuristics can be used to avoid full construction [McIlraith+Son 02] Generic compositions + customization – develops mapping of DAML-S into ConGolog, and uses to create compositions – Approach based on 2-level hierarchy…

35 October 18, 2003 Behavioral Signatures and E-Service Composition 35 Composition for Mealy Peers Traditional synthesis problem statement: – Given: ec-schema and LTL formula – Create: an fsa for each peer so that is satisfied Synthesis results for Mealy implementations with bounded queues – Closed compositions: folklore results imply that synthesis is decidable Propositional LTL description PSPACE -regular set represented as automaton PTIME – Open compositions: Undecidable for LTL for arbitrary ec-schemas [Pnueli+Rosner 90] Decidable for hierarchical topology, but non- elementary even for linear case [Kupferman+Vardi 01]

36 October 18, 2003 Behavioral Signatures and E-Service Composition 36 Reformulation of the Synthesis Problem to use extended UDDI Repository UDDI Repository: globally accessible store for web service descriptions and locations – Imagine that it supports Mealy descriptions Possible approach – Given: ec-schema, LTL formula, UDDI repository – Find: peers in repository so that is satisfied Variation: allow creation of a mediator to choreograph the selected peers Database aspect of this problem – How to search across large space of Mealy descriptions? – What is appropriate query language?

37 October 18, 2003 Behavioral Signatures and E-Service Composition 37 Synthesis for Unbounded, Closed Case [Bultan et. al. 03] Use conversation language to express global behavior Problem statement: – Given: ec-schema and regular language L over messages – Create: an fsa for each peer so that composition generates L = join-prepone closure of L Result: Mealy peers can be constructed whose composition gives global behavior L – Do a projection on fsa accepting L Can again ask UDDI version of synthesis question

38 October 18, 2003 Behavioral Signatures and E-Service Composition 38 Recent work from Lenzerinis group (DL 03) Based on a different model for peers – Focus on sequences of actions, not messages – Includes a user who repeatedly makes choice (from limited set) about next action she wants – All actions visible at top level Abstract behavior of the Service: Do until Client selects End 1. Give Client a choice of actions to be performed 2. Wait for Client choice 3. Perform action chosen by Client Client Service on-line music store Actions that client can ask for: initiate, end search listen cart buy [Berardi et al 03]

39 October 18, 2003 Behavioral Signatures and E-Service Composition 39 Using standard automata techniques: NEXPTIME Using reduction to ALU DL: EXPTIME Solve composition by synthesizing mediator Assuming peers and spec are regular, can – Determine if a composition exists – If one does, then select peers and construct mediator Desired behavior (as FSA) Extended UDDI Mediator (constructed) Services (selected from UDDI )

40 October 18, 2003 Behavioral Signatures and E-Service Composition 40 Conclusions Sequential behavior and messaging are a fact of life – We need a notion of behavioral signature Automata-based perspective – Provides formal framework that incorporates events and sequencing – Can draw on broad theory of analysis tools – Offers a framework for automated composition – Can represent (at least some) in DLs – link to OWL? Automata-based perspective should be exploited in semantic web services Results suggest key challenges in composition – Select peers: queries over sets of peers – Mediator crucial: find/build the mediator

41 October 18, 2003 Behavioral Signatures and E-Service Composition 41 We are just getting started … Enhanced Mealy – can we incorporate – Messages + actions – Pre-/post-conditions á la OWL-S – Hierarchical structure for messages (state charts?) – Temporal constraints – (your favorite) PSL constructs Composition of Mealy ++ machines – Can we adapt the Roman approach ? – Augment traditional planning with approach for cyclic behaviors Mealy ++ vis-à-vis BPEL4WS, OWL-S process model, PSL, FIPA A-UML, … – Jianwen Su et. al. developing tool for translating between Mealy and BPEL4WS Searching a large set of Mealy ++ signatures – What is appropriate query language? Finding relevant results from various communities: verification, -calculus, planning, DL, DB, agent, …

42 October 18, 2003 Behavioral Signatures and E-Service Composition 42 Backup Slides

43 October 18, 2003 Behavioral Signatures and E-Service Composition 43 E-Services The Web: Flexible human-machine interaction E-services: Flexible machine-machine interaction Working Definition: Network-resident software services accessible via standardized protocols – Simple Object Access Protocol (SOAP): very flexible remote procedure call Lots of interest in trade press, academic community, standards bodies,... Applications in e-commerce, telecom, science, GRID, government, education,...

44 October 18, 2003 Behavioral Signatures and E-Service Composition 44 E-Science E.g., find best location for waste treatment plant Possibly 100s of nodes, and running for weeks Data size difference: – Control and calibrations (small) – Experimental data (large) Provenance: need to access derivation history notifications and/or experimental data control and calibrations Atmo- spheric Simu- lation Sea Circu- lation Waste Transport Controller

45 October 18, 2003 Behavioral Signatures and E-Service Composition 45 Web Services Protocol Stack* *Based on [van der Aalst 03] Transport layer: HTTP, SMTP, FTP, etc. XML messaging layer: SOAP Service Description Layer: WSDL, WSCL, WSCI Web service composition: WSFL, XLANG, BPEL4WS, BPML, W3C Choreography Publishing and discovery: UDDI

46 October 18, 2003 Behavioral Signatures and E-Service Composition 46 Pre-/post-conditions DAML-S provides for pre- and post-conditions Examples – if valid client sends Order, then Bill is created – if Payment is received, then Receipt is sent Performing inference (everything else fixed) – Assume a Bank service such that: if bill received and sufficient funds, then payment is sent – Then we can infer that: an order from a valid client with a sufficient account balance will result in a receipt Reasoning with pre- and post-conditions – Different models will lead to different complexity – [Narayanan+McIlraith 02] axiomatization in situation calculus for a Petri-net based model Complexity from PTIME to EXPSPACE-hard order receipt bill payment Supplier

47 October 18, 2003 Behavioral Signatures and E-Service Composition 47 Web Services Conversation Language (WSCL) Alternative automata-based approach for describing behavior of e-services – States are the WSDL operations (input and/or output) – Transitions are pairs of operations, with associated condition Condition refers to type of documents passed as input or output Relationship of Mealy machine vs. WSCL machine remains open – Mealy machine formalism given above could be extended to include conditions based on types of documents passed – Number of states in WSCL machine bounded by number of WSDL operations – So Mealy machines (with conditions) appear more expressive than WSCL machines

48 October 18, 2003 Behavioral Signatures and E-Service Composition 48 Technical Definition A Mealy peer is an FSA M T, s, F in, out, – T : a set of states – s : the initial state – F : a set of final states – in : input message classes – out : output message classes – : transition relation that either consume an input, (s, ?m, s ), or produce output, (s, !m, s ), or make an empty (internal ) move, (s,, s )

49 October 18, 2003 Behavioral Signatures and E-Service Composition 49 Abstract model for e-services with data Variation of relational transducer [Abiteboul et al 00] Extend Mealy machine to (Q,q 0, F, I, H, O, ) – Input schema I (can hold data associated with incoming messges) – Internal/hidden schema H – Output schema O – has tuples (q, q, G, T) G is guard -- boolean query on I and H T is transform - queries that create new H and output O Can use different data models (relational, XML, …) General decision problems are undecidable – E.g., if use relational calculus as data manipulation language Restricted cases are decidable, tractable – E.g., reachability of a state, if using conjunctive queries – E.g., Spocus transducers of [Abiteboul et al 00] have PTIME decidability results

50 October 18, 2003 Behavioral Signatures and E-Service Composition 50 Data Transducers as White-Box Peers Add database to fsa (XML, relational) Store e-service with – Customer_care – Inventory_replenishment – Store_database used as shared data store Cf., XL [Florescu et.al.03] – Process + XQuery Cf., Relational Transducer [Abiteboul et. al. 00] – Analysis undecidable; NEXPTIME for restrictions !o1!o1 !o2!o2 ?r2?r2 ?r1?r1 !o2!o2 !o1!o1 ?r1?r1 ?r2?r2 !a!a ?k?k okok authorize take buy receipt 1 order 1 receipt 2 order 2 ?y?y !t!t inventory_ replenishment customer_care store_inventory partqty... store_database

51 October 18, 2003 Behavioral Signatures and E-Service Composition 51 Parting Challenge: Process + Data Develop a theory for e-service composition that incorporates process + data store bank warehouse1 E.g., Relational Mealy Machines (or XML,... ) – Cf. Relational Transducers of [Abiteboul et. al. 00] – Focus on restricted query/update languages Extend results previously obtained to include variables, context, large data warehouse2

52 October 18, 2003 Behavioral Signatures and E-Service Composition 52 Computerised facilitation or automation of a business process, in whole or part [WfMC] Centralized control – State of conversation maintained by WF manager E-service Glue Languages and Workflow Management Delegation of almost everything to the app.s – E.g., application data is not accessible to WF manager Workflow standardization has mixed success – Web services must interoperate standard likely – Should focus on interfaces, not internals

53 October 18, 2003 Behavioral Signatures and E-Service Composition 53 ActiveXML: A data-centric white-box language [Abiteboul et.al. 03] A novel combination of data and web services Three ways to treat remote data: – Remote data is virtual, and materialized when queried – Pass data pointer as part of query response – Materialize remote data periodically Alternative to control-flow based languages: – Outer process flow dictated by XML query language (and structure of data) – Remote procedure calls embedded into XML structure

54 October 18, 2003 Behavioral Signatures and E-Service Composition 54 White-box Analysis via XML Many different kinds of constraints arise in BPEL4WS spec a)Referential: service links refer to peers in composition b)Cardinality: for synchronization links, 1 source and 1 target c)Structural: internal synchronization links dont cross while scopes d)Value-based: requests matched by responses e)XPath: query on variable is subtype of a target variable For (a): XML Schema suffices For (b) - (d): see [Deutsch+Tannen 01, Benedikt et.al. 02] For (e): Involves a combination of XPath and control flow analysis – If XL used, then everything is XQuery, and so XQuery type-checker can assist with type correctness

55 October 18, 2003 Behavioral Signatures and E-Service Composition 55 AZTEC: A white-box language for sessions and asynchronous events [Christophides et. al. 01a] Control is hub-and-spoke Maintains state of sessions – Richer than web-service notion of conversation Queue for incoming asynchronous events Launches instance of event-handling flowchart for each external event Synchronization between flowcharts – Priority – Via shared data – Can interrupt other flowcharts (e.g., if prepay account runs out of money) Profile Data Presence Server Media Server (voice) Media Server (video) Pre-Pay Session Coordinator

56 October 18, 2003 Behavioral Signatures and E-Service Composition 56 Agent UML E.g., [Odell 00] An exploration of different ways that UML can be used to capture agent interactions Message types based on KQML – request, assert, refuse, … – Subset of messages relevant to e-commerce, alerting services, long-running activities, supply chain life-cycle, manufacturing life-cycle, collaborative technologies, pervasive computing, … Winograd-Flores perspective (classical)

57 October 18, 2003 Behavioral Signatures and E-Service Composition 57 A-UML: focus on modeling Diff. levels: Global, interaction, internal Focus not on analysis or automated composition Collaboration Diagram Activity Diagram (with Swim Lanes and Object Flow) Sequence Chart Nesting (mix & match) Packages (with nesting) [for global aspects]

58 October 18, 2003 Behavioral Signatures and E-Service Composition 58 A Roman approach to composition that bridges to DLs [Berardi et al 03] fulfill_ order 1 authorize_ line_of_credit Higher level of abstraction than messages Enactments still have different life-cycles store bank supplier1 supplier2 pay_ supplier 1 Based on an action-based model E-commerce example, with focus on actions sell_goods

59 October 18, 2003 Behavioral Signatures and E-Service Composition 59 Focus on one Client, one Server Online Music Store Front- end Drill down on customer buying CDs Examine sub-actions inside sell_goods Back- end Abstract behavior of the Service: Do until Client selects End 1. Give Client a choice of actions to be performed 2. Wait for Client choice 3. Perform action chosen by Client on-line music store Client Service initiate search listen cart buy end

60 October 18, 2003 Behavioral Signatures and E-Service Composition 60 Execution Tree in Roman model (External) execution tree: all possible sequences of actions supported by service on-line music store... initiate search cart listen search cart buy search Client Service Action supported by service State at which client can stop State at which client can not stop Children labeled by distinct actions Tree is equivalent to a language over actions – Typically, focus on regular languages

61 October 18, 2003 Behavioral Signatures and E-Service Composition 61 Composition in Roman Model (sketch) Internal execution tree holds actions by server and delegates of that server on-line music store Client Service delegates cust. care bank All actions are visible to client; none internal... initiate, care search, care cart, care listen, juke search, care cart, care buy, bank search, care jukebox

62 October 18, 2003 Behavioral Signatures and E-Service Composition 62 Composition in Roman Proposal [Berardi et.al.03] If trees regular, can build composition (if exists) – Includes selecting delegates and constructing mediator Using standard automata techniques: NEXPTIME Using reduction to ALU DL: EXPTIME on-line music store cust- care bankjukebox External tree for store... initiate search cart listen search cartbuy search... initiate, care search, care cart, care listen, juke search, care cart, care buy, bank search, care listen buy External trees for cust-care, jukebox, bank... initiate search cart search Internal tree for store

63 October 18, 2003 Behavioral Signatures and E-Service Composition 63 Citations [Abiteboul et. al. 00] S. Abiteboul, V. Vianu, B. Fordham, and Y. Yesha. Relational Transducers for electronic commerce. JCSS, 61(2): , 2000 [Abiteboul et.al. 03] S. Abitegoul, A. Bonifati, G. Cobena, I. Manolescu, and T. Milo. Dynamic XML documents with distribution and replication. SIGMOD, 2003 [Benedikt et.al. 02] M. Benedikt, G. Bruns, J. Gibson, R. Kuss, and A. Ng. Automated update management for XML integrity constraints. Proc. Workshop on Programming Languages for XML (PLAN-X), 2002 [Berardi et al 03] D. Berardi, D. Calvanese, G. De Giacomo, M. Lenzerini, and M. Mecella. E-Service Composition by Description Logics Based Reasoning. Proc Description Logics workshop (DL 2003). [Bultan et.al. WWW03] T. Bultan, Z. Fu, R. Hull, and J. Su. Conversation Specification: A new approach to design and analysis of e-service composition. WWW, 2003 [Christophides et. al. 01a] V. Christophides, R. Hull, G. Karnounarakis, A. Kumar, G. Tong, and M. Xiong. Beyond discrete e-services: Composing session-oriented services in telecommunications. Proc. Workshop on Technologies for E-Services (TES), Springer LNCS 2193, Sept, 2001

64 October 18, 2003 Behavioral Signatures and E-Service Composition 64 Citations (cont) [Christophides et. al. 01b] V. Christophides, R. Hull, and A. Kumar. Querying and splicing of XML workflows. CoopIS, 2001 [Clarke et.al. 00] E. Clarke, O. Grumberg, and D. Peled. Model Checking. MIT Press, [Deutsch+Tannen 01] A. Deutsch and V. Tannen. Containment for classes of XPath expressions under integrity constraints. Proc. Workshop on Knowledge Representation meets Databases (KRDB), 2001 [Florescu et.al.03] D. Florescu, A. Gruhagen, and D. Kossmann. XL: An XML programming language for web service specification and composition. WWW, 2002 [Kupferman+Vardi 01] O. Kupferman and M. Y. Vardi. Synthesizing distributed systems. Proc. IEEE Symp. Logic in Computer Science (LICS), 2001 [McIlraith+Son 02] S. A. McIlraith and T. C. Son. Adapting Golog for Composition of Semantic Web Services. KR 2002 [Narayanan+McIlraith 02] S. Narayanan and S. A. McIlraith. Simulation, verification and automated composition of web services. WWW 2002

65 October 18, 2003 Behavioral Signatures and E-Service Composition 65 Citations (cont) [Odell 00] J. Odell, Specifying Agent Interactions using UML. Presentation to July, 2000, meeting of FIPA. Aug_2000.pdf [Pnueli+Rosner 90] A. Pnueli and R. Rosner. Distributed reactive systems are hard to synthesize. FOCS, 1990 [van der Aalst 03] W. M. P. van der Aalst. Dont go with the flow: Web services composition standards exposed. IEEE Intelligent Systems, Jan/Feb, 2003 [WfMC] Workflow Management Coalition.


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