Enterprise Service Computing From Concept to Deployment_7 pptx

Definition 23: Local History In terms of our three-point service-oriented design and modeling methodology for Web-services composition, on the conceptual system level, given two services

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Within one life cycle of one transaction, if one canceling occurs at one of the three phrases (C, M, F), it can be expressed by equation 3

Here we call the semantic consistency of T1 the first layer of semantic consistency within the Web-services conversation, and the semantic consistency of T2 the second layer of semantic consistency

To define such a conversation, we rely on a set of services (A, B ∈ Service) and a set

of document types (T1 ∈ Type) We do not explicitly define the type of the system associated with the messages exchanged between documents, but it encompasses the type of the system for XML

is, the elements of a typed interaction history include the types of information that may be exchanged in a conversation We map a given conversation to a set of typed interaction histories, and the value and type of the message container within the conversation We then define a notion of conformance between interaction histories and typed interaction histories

A-• A-S(T2:T1(v)) represents the action that service A sends a value v that matches

or validates against the templates of T2 and T1,

• A-R(T2:T1(v)) represents the action that service A receives a value v that matches or validates against the templates of T2 and T1,

• A-A(T2:T1(v)) represents the action that service A aborts a send of a value v that matches or validates against the template of T2 and T1, and

• A-C(T2:T1(v)) represents the action that service A commits a send of a value

v that matches or validates against the template of T2 and T1

Three-Pont Servce-Orented Desgn and Modelng Methodology for Web Servces 

Definition 13

The set of the valid typed interaction history T is defined as follows

1 λ ∈ T.

2 For any typed action E and typed interaction history t ∈ T, E.t ∈ T

A typed action E is said to occur in a typed interaction history t if t = t1.E.t2 We write E ∈ t if typed action E occurs in typed interaction history t

In essence, a typed interaction history is like an interaction history except for the fact that it has templates of documents or types of the values associated with the actions as opposed to the actual values themselves

Definition 14

Given an interaction i of the form A → B: T2: T1(v), the interaction semantics of i

is the set {A-S(T2:T1(v)).A-C(T2:T1(v)).B-R(T2: T1(v))} We write i ⇒ S if S is the semantics of the interaction i

This typed interaction history captures the fact that one of the end points of the interaction did a successful send followed by a commit, while the other end of the interaction did a successful receive

Definition 15

Given two sets of typed interaction histories T1 and T2, the concatenation T of T1 and

2

T (written as T = T1.T2) is defined as a set of sequences whose elements are made

by concatenating any elements of the first set with any element of the second set

Definition 16

Given a conversation definition of the form c = i1;c', where i1 is a simple

interac-tion of the form A → B: T2: T1(v) and c' is a conversation fragment, c' can be the interaction fragment or the evaluation of a holder function, or it can be both the interaction fragment and the evaluation of a holder function Suppose further that

i1 ⇒ S i1 and c' ⇒ S c' The set S c such that c ⇒ S c is defined as S c = S i1 ⋅S c'

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The.Formal.Semantics.of.the.Standard.Schemes

In terms of the standard schemes for the ordering service of an order-handing system (one supplier) and Definitions 13 and 15, we would like to address the formal seman-tics of the standard schemes on the conceptual system level by taking the example

of the ordering service of an order-handing system In this chapter, the definitions

of schemes have general meanings and are not limited to a concrete example

Three-Pont Servce-Orented Desgn and Modelng Methodology for Web Servces 

The Formal Semantics of Scheme D

For Scheme D, the conversation fragment including records of matching message holders and received messages is:

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to take one of three activities (C, M, F), its activity needs to obtain the agreement

of the other parent role and be confirmed by the intermediary role

Correspondingly, the semantics of the conversation with the interaction semantics are the following

Three-Pont Servce-Orented Desgn and Modelng Methodology for Web Servces 

Scheme.G: One buyer would like to book goods and sends the order message This

piece of information is passed to the supplier by the agent At the same time the agent is preparing to send this message to supplier (denoted as ||), the buyer wants

to cancel the order and sends the canceling information to the agent We assume the buyer has priority over the supplier, denoted as Buyer ∠ Supplier

Buyer → Agent: C: Order(a);

Holder(Orderline-mess-holder) = C: Order (a);

Agent → Supplier: C: Order(a) || Buyer → Agent: QC: Order(a)

When evaluating Holder(Product-mess-holder),

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Scheme.H: The buyer would like to change the content of the booking and sends

the modified message This piece of information is passed to the supplier by the agent At the same time the agent is preparing to send this message to supplier, the buyer wants to cancel this change and sends the canceling information to the agent

We assume the buyer has priority over the supplier

Scheme.I: The Supplier fulfills the contract This piece of information is passed to

the buyer by the agent At the same time, the buyer cancels the order (we assume the buyer has priority over the supplier) Therefore, the order is not fulfilled by the supplier (Within one transaction, this canceling may occur in one of the three phases C, M, or F.)

The semantics of Scheme H and Scheme I can be represented as those of Scheme G

sup-Three-Pont Servce-Orented Desgn and Modelng Methodology for Web Servces 

Definition 20

Because the semantics of the canceling means there is no possibility of success, the parts of Scheme G, Scheme H, and Scheme I are the same as those of Scheme

D, Scheme E, and Scheme F

Correspondingly, the semantics of Scheme D from evaluating mess-holder) are the same as those of Scheme G The semantics of Scheme E from evaluating Holder(Product-mess-holder) are the same as those of Scheme H, and the semantics of Scheme F from evaluating Holder(Order-mess-holder) are the same as those of Scheme I

Holder(Product-In summary, the formal semantics of the ordering of an order-handling system of one supplier can be summarized in the following table

• SP = (*S c)1⋅(*S M )i⋅(*S F)1,

where i is a finite integer

Formal.History.Conformance

Local.History.Conformance.to.Schemes

In Definition 6 and Definition 7, we formally defined the valid interaction history

In Definition 12 and Definition 13, we formally defined the valid typed interaction history We also formally defined local typed traces, which we call the formal se-mantics of schemes (in terms of the ordering service of an order-handling system of

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one supplier) In the following, we first define the local history, and then we define the local history conformance to the formal semantics of schemes

Definition 23: Local History

In terms of our three-point service-oriented design and modeling methodology for Web-services composition, on the conceptual system level, given two services A and

B and their message holders, we define the local history (denoted as lh) to be a set

of history scripts, which includes all the values of the message holder function, the valid interaction history, the evaluating message holder, and the reasoning scripts from Service A to Service B

The conformance relation has two aspects There is a structure aspect, requiring that the sequences agree between a local history and the formal semantics of a scheme, which includes the sequence of interactions, the matching or validating of the holder value, the evaluation of the holder, and the reasoning results There is also a value aspect, which requires that the data exchanged as part of the history match or validate against the templates in the formal semantics of the schemes

Definition 26: Well-Formed Local History

A local history is said to be well formed if it conforms to the formal semantics of one of the schemes (Scheme A…Scheme I)

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Successful History of One Life Cycle of One Transaction

Definition 27: Successful History of One Life Cycle of One Transaction

In Definition 22, we defined the successful standard semantics specification of a system within one life cycle of one transaction Here we define the successful history

of one life cycle of one transaction A history (denoted as His) of one life cycle of one transaction is said to be successful if one of the following conditions holds

A: If there is no modification within one life cycle of one transaction, then

[lh1 ≈ (*S C)]1.[lh2 ≈ (*S F)]1 (4)

B: If there are i (i ≥1) modifications within one life cycle of one transaction, then

[lh1 ≈ (*S C)]1 [lh2 ( 1 +i) ≈ (*S M)]i [lh ( i2 + ) ≈ (*S F)]1, (5)

where i (i ≥1) is a finite integer

According to Definition 17, Definition 18, and Definition 19, a successful history

of one life cycle of one transaction can be expressed in one of the following sions as well

expres-A: If there is no modification within one life cycle of one transaction, then

[lh1 ≈ st (Scheme A)]1.[lh2 ≈ st (Scheme C)]1 (6)

B: If there are i (i ≥1) modifications within one life cycle of one transaction, then

[lh1 ≈ st (Scheme A)]1 [lh2 ( 1 +i) ≈ st (Scheme B)]i [lh ( i2 + ) ≈ st (Scheme C)]1, (7)

where i (i ≥1) is a finite integer

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System History Conformance

Definition 28: Well-Formed History of One Life Cycle of One Transaction on the.System.Level

We are interested in defining a well-formed history of one life cycle of one tion on the system level because if we have this definition, we can avert the non-well-formed system behaviors that can be tested and found on the system level for Web-services composition

transac-A history of one life cycle of one transaction is said to be well formed if one of the following conditions holds

where i (i ≥1) is a finite integer

where i (i ≥1) is a finite integer

In terms of our three-point service-oriented design and modeling methodology for Web-services composition, given the fact that there is a service buyer and service supplier, the intermediary service is the service agent

When equation 8 happens within one life cycle of one transaction, the service buyer does not successfully create an order

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When equation 9 happens within one life cycle of one transaction, the service buyer first successfully creates an order, but later cancels the order

When equation 10 happens within one life cycle of one transaction, the service buyer first successfully creates an order, but later does not successfully modify the order

When equation 11 happens within one life cycle of one transaction, the service buyer first successfully creates an order, but later cancels the Order during the modifying phase

When equation 12 happens within one life cycle of one transaction, the service buyer

successfully creates and modifies an order i (i ≥ 1) times, but the service supplier

does not fulfill the order in the end

When equation 13 happens within one life cycle of one transaction, the service

buyer successfully creates and modifies an order i (i ≥ 1) times, but later cancels

the order during the fulfillment phase under the condition that the service buyer has priority over the service supplier

When equation 14 happens within one life cycle of one transaction, the service buyer and service supplier successfully complete one life cycle of one transaction without modifying the order

When equation 15 happens within one life cycle of one transaction, the service buyer and service supplier successfully complete one life cycle of one transaction

and modify the order i (i ≥ 1) times.

According to Definition 17, Definition 18, and Definition 19, a well-formed history

of one life cycle of one transaction can be expressed as well in one of the following expressions:

.[lh2 ≈ st (Scheme E)]1

(18) d: [lh1 ≈ st (Scheme A)]1

.[lh2 ≈ st (Scheme H)]1

e: [lh1 ≈ st (Scheme A)]1

[lh2 ( 1 +i) ≈ st (Scheme B)]i.[lh ( i2 + ) ≈ st (Scheme F)]1

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where i (i ≥1) is a finite integer,

Proof.Sketch

This can be proven by a straightforward induction on the length of lh or by ing the decision procedure

construct-Theorem.2

Given the formal semantics of one of the schemes st (Scheme A…Scheme I) and

a local history lh such that ≠ [lh ≈ st(Scheme A…Scheme I], there is a istic procedure to determine the first mismatch between them that causes ≠ [lh ≈

determin-st(Scheme A…Scheme I].

This property essentially ensures that there is a way to determine the cause of the deviation of a local history from the formal semantics of one of the schemes

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Essentially, these two theorems tell us that it is possible to decide whether a local history conforms to the formal semantics of one of the schemes In addition, if a local history does not conform to the formal semantics of one of the schemes, we can determine the first cause of nonconformance These properties therefore provide

a basis of managing and testing Web-services interactions

Related.Works

There are many emerging Web-services standards that are relevant for our work

We enumerate some of major work and briefly describe the relationship with our work

• BPEL4WS: BPEL4WS (Business Process Execution Language for Web Services

Version 1.1, 2003) has emerged as a proposal for describing business-process

execution BPEL4WS is built on top of the Web-services architecture, and

it is a richer, expressive services-composition language in which business protocols can be expressed Because it is a machine-executable language and

is implementation oriented, it does not explicitly address the composition logic and lacks a clear analysis of the relationships between services and the relationships between messages Our work makes up for its insufficiency from the high level, providing a set of sound analysis, design, and modeling methodologies for Web-services composition and making clear the semantic consistency within Web-services interactions on the concept level and system level Its results are significant and profound, and they can be the solid theo-retical foundation of the BPEL4WS’ further evolution

• WSCL: The work on WSCL (Web Services Conversation Language (WSCL) 1.0, 2002) proposes a conversation language for Web-service protocols and

frameworks It focuses on modeling the sequencing of the interactions or operations of one interface and fills the gap between mere interface definition languages that do not specify any choreography and more complex process or flow languages that describe complex, global, multiparty conversations and processes Also, its conversation definitions are themselves XML documents and can be interpreted by Web-service development tools However, its work lacks the semantic analysis, design, and modeling on the semantic consistency

of Web-services conversation on the logic level and on the system level, and clear and accurate formal constructs Therefore, our work can provide a good complement for its insufficiency in semantic consistency within Web-services conversations, and at the same time, provides the formal underpinnings for Web-services conversation and Web-services composition

• MERODE (Lemahieu, Snoeck, Michiels, & Goethals, 2003; Lemahieu, Snoeck, Michiels, Goethals, Guido, & Vandenbulcke, 2003; Snoeck & Dedene, 1998;

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Snoeck, Dedene, et al., 1999; Snoeck et al., 1999): Our work has some tion with the research results in MERODE MERODE is the object-oriented analysis and design methodology for enterprise modeling Its first-class enti-ties are object types and event types It requires that all relationships express existence dependency in object types, thus this methodology provides the key

connec-to semantic integrity among object types through presenting the existence dependency in object types Our work caters to the need of new Web-services computing and regards Web services as first-class entities Our work enhances the concepts of semantic consistency in MERODE in the Web-services world, whose improvement is profound and significant

• Other research: Bultan, Fu, Hull, and Su (2003) and Hull, Benedikt, tophides, and Su (2003) have proposed a mealy-machine-based formalism

Chris-to express the behavior of Web services A mealy machine can express the behavior of a Web service as sequences of interactions, where the sequences are constructed by sequential composition and nondeterministic choice The research results in their works provide a good reference for the formal model of Web-services composition Although this mealy-machine formalism provides the description about the internal behavior of a service, it lacks the direct analy-sis, discussion, and expression on the semantic consistency of Web-services interactions and composition

Conclusion

In order to tackle one of the big inhibitors of Web-services adoption and tance—the lack of semantic consistency in business processes within Web-services interactions and composition—in this chapter we proposed a novel analysis, design, and modeling methodology for Web-services composition: a three-point service-oriented methodology based on some object-oriented research results in MERODE

accep-On the concept level, we first clarified the research issue of semantic consistency within Web-services interactions and Web-services composition, and at the same time,

we precisely defined and demonstrated the semantic consistency of Web-services composition on the logic level and system level through demonstrating the standard schemes of an order-handling system Therefore, we made major contributions to the research area of Web-services composition

In the future, there are some possible directions for our further research For instance,

we can extend our work both in practical and theoretical directions On one side, we can develop a prototype system that implements the methodology for Web-services composition presented in the chapter Such a system will enable us to implement the composition techniques for Web-services composition and test whether the