output-inputppt输出inputppt

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1、Should Mirror Operations Be Dropped? David Booth W3C Fellow / Hewlett-Packard Current Status Four Message Exchange Patterns (MEPs): Input-Output (was Request-Response) Input-Only (was One-Way) Output-Input (was Solicit-Response) Output-Only (was Notification) Mirror ops: Output-Input, Output-Only Pr

2、oblems with Mirror Ops 1. Multiple interpretations: event? callback? 2. Little evidence of use 3. Where to get the Clients address? 4. Inconsistent treatment of Faults? Input-Output: Fault is an alternate Output Input-Only: (no Faults) Output-Input: Fault is an alternate Input Output-Only: (no Fault

3、s) What I Did Abstract analysis: Suppose we used WS descriptions in a larger context. Would we want mirror ops? Example: Markets Potential Application: Markets Multiple Clients, Multiple Services Any Client can talk to any Service (of the same type) Service A3 Service A2 Client A1 Service B3 Service

4、 B2 Service B1 Markets Ways to match Client and Service: Client and Service share same WSDL Client and Service have complementary WSDLs Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 Shared Service Descriptions Role must be separately indicated: Client: Im a T Client Service: Im a

5、T Service Binding information is lopsided (Service-centric) Binding has Service-specific info (address) Where is Client-specific info placed? Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 T Shared: One WSDL per Service T1, T2, T3 could be specific to B1, B2, B3 T1 has B1s address,

6、 T2 has B2s address, etc. B1: Im a T1 Service B2: Im a T2 Service, etc. Each Client could reference all T1, T2, T3: Im a T1Client, a T2 Client and a T3 Client Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 T3 T2 T1 Shared: Referencing a Common T T1, T2, T3 could reference generic T

7、 T1 has B1s address, T2 has B2s address, etc. B1: Im a T1 T is Service-centric, but not identity-centric (I.e., no address) Client could reference generic T: Im a T Client Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 T3 T2 T1 T TA3 TA2 Shared: Client, Service Ref T TA1, TA2, TA3,

8、 TB1, TB2, TB3 are all identity-specific TA1: A1 is a T Client TB1: B1 is a T Service T does not contain address Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 TB3 TB2 TB1 T TA1 TA3 TA2 Shared: Role-Specific Descriptions TC and TS are role-specific, but not identity-specific: TC: I

9、 am a T Client TS: I am a T Service T does not contain address or role info Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 TB3 TB2 TB1 T TA1 TC TS TA3 TA2 Shared: Conclusion Sharing requires mirror ops only if you think theyre important Need Output-Input? Need Output-Only? Service

10、A3 Service A2 Client A1 Service B3 Service B2 Service B1 TB3 TB2 TB1 T TA1 Complementary Service Descriptions Symmetric (Peer-to-Peer) T describes Service; T describes Client T, T indicate: Generic info (T) Role-specific info (Client vs. Service) Identity-specific info (address) Requires (complement

11、ary) equivalence to match T T Service B3 Service B2 Service B1 Service A3 Service A2 Client A1 Complementary: Observation Complementary approach requires mirror ops Inputs of T are Outputs of T Outputs of T are Inputs of T T T Service B3 Service B2 Service B1 Service A3 Service A2 Client A1 TA3 TA2

12、Complementary: Identity-Specific Info TA1, TA2, TA3, TB1, TB2, TB3 are all identity-specific TA1: A1 is a T TB1: B1 is a T T, T do not contain addresses Service A3 Service A2 Client A1 Service B3 Service B2 Service B1 TB3 TB2 TB1 T TA1 T Conclusions Mirror ops add flexibility Identity-specific info

13、(address) should be separated from shared info Other binding info can be shared: transport protocol, etc. END WSDL Information Sharing From most shared to least shared: 1. Message types 2. Message direction (input/output) 3. Transport protocol, Message encoding 4. Address (Not shared!) The least sha

14、red info should be latest bound Observations on MEPs MEPs Sequence: 1. A sends W to B 2. B sends X to A 3. A sends Y to B 4. B sends Z to A X Y Z W 1 2 3 4 Bs View As View MEP: Bs View One big MEP: PWXYZ: Receive W, send X, receive Y, send Z Bs View X Y Z W 1 2 3 4 As View PWXYZ MEP: Bs View Two Req

15、uest-Response MEPs: PWX: Receive W, send X PYZ: Receive Y, send Z Bs View X Y Z W 1 2 3 4 As View PWX PYZ MEP: Bs View Q: Should B care how A models its interactions with B? A: Of course not. Bs View X Y Z W 1 2 3 4 As View PWX PYZ MEP: As View 1 Two Solicit-Response MEPs: PWX: Send W, receive X PYZ

16、: Send Y, receive Z Bs View X Y Z W 1 2 3 4 As View PWX PYZ MEP: As View 2 Three MEPs: PW: Send W (Notification) PXY: Receive X, send Y (Request-Response) PZ: Receive Z (One-way) Bs View X Y Z W 1 2 3 4 As View PXY PW PZ MEP: As View 3 Four MEPs: PW: Send W (Notification) PX: Receive X (One-way) PY:

17、 Send Y (Notification) PZ: Receive Z (One-way) Bs View X Y Z W 1 2 3 4 As View PX PW PZ PY MEP: As View 4 Two MEPs: PWX: Send W, receive X (Solicit-Response) PYZ: Send Y, receive Z (Request-Response) Bs View X Y Z W 1 2 3 4 As View PWZ PXY MEPs Are Relative Observation: MEPs are role-specific Bs Vie

18、w X Y Z W 1 2 3 4 As View PWZ PXY PWX PYZ MEPs Are Relative A makes PWZ from half of PWX and half of PYZ Bs View X Y Z W 1 2 3 4 As View PXY PWX PYZ PWZ MEPs Are Relative A makes PXY from half of PWX and half of PYZ Bs View X Y Z W 1 2 3 4 As View PWZ PXY PWX PYZ Role-Specific Information Service B

19、Service A Role-Specific Information Suppose: A must send B messages in format X X represents message format definition A, B reference X X contains role-specific information, e.g., (from Bs perspective) A, B use the same software T to generate Sender and Receiver from X Receiver Sender X T Service B

20、Service A Role-Specific Information Observation: Q: How does T know whether to generate Sender or Receiver from X? A: T must have other information Therefore is unnecessary in X Receiver Sender T X Service B Service A Role-Specific Information Conclusion: Information that is shared between different roles should not contain role-specific information Examples of role-specific information: , , one-way, address Receiver Sender T X