E-commerce Architecture

8.1 E-commerce Architecture

8.1.1 Infrastructure

The infrastructure of e-commerce is shown as Fig. 8.1.

Figure 8.1 Infrastructure of e-commerce In the infrastructure of e-commerce, e-commerce entity A submits a business

request, and sends request information and bank account information to the e-commerce application service center provided by the e-commerce ASP through the Internet; the intelligent search engine searches the appropriate trade entity B on the Internet, and sends the request information to entity B through the Internet; after entity B receives the request from entity A, entity B responds to the trading request after analyzing and handling, and then sends the response information and its bank account information to the e-commerce application service center after analyzing and handling with the request; after receiving entity B’s trading request, the e-commerce application service center authenticates identities of both sides, and sends the authenticated bank account information to the banks, which they open their accounts through payment gateway, and then completes bank account transformation through bank private network; the transferred information is sent to the trading entities through the e-commerce application service center; the delivery is completed with the help of some cooperated organizations, such as industry and commerce, revenue, CIQ, law and transportation.

The e-commerce infrastructure can be divided into two relatively independent sub-systems. They are e-commerce security sub-system and e-commerce payment sub-system. The e-commerce security sub-system is in charge of handling security issues of information interaction in the e-commerce trade process, including the security issues between the internal Internet subnet of the e-commerce entity and the Internet, between the Internet and the e-commerce application service center, and between the e-commerce application service center and the payment sub-system,

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etc.; the e-commerce payment sub-system is in charge of handling the electronic payment issues in the e-commerce trade process, which integrates the payment part in the trade process with the Internet, realizing a digital, electronic and automatic payment process, clearing away obstacles and paving road for completely implementing of e-commerce in every aspect of everyday life.

The figure above briefly illustrates the Infrastructure of e-commerce system, and the functions of each part and relations between sub-systems of the e-commerce infrastructure. It simplifies the security sub-system and the payment sub-system. There are details about the security and payment sub-systems in the following chapters. Next, we will specify the infrastructure of e-commerce on the view of data structure and Petri net modeling, then make out the data flow and process control method of the structure.

8.1.2 Data Flow of Infrastructure

The whole framework of the e-commerce infrastructure includes the realization of the functions of every part, communication relations of the parts and sub-system division. This section gives a clear representation of communication relation of different parts from the perspective of the data flow diagram, and describes the information flow; data flow and control method in the data flow diagram using PASCAL-like language. And deals with the content of security sub-system and payment sub-system with the absolutely similar method of structural description.

The data flow diagram of e-commerce infrastructure is shown as Fig. 8.2, in which A and B are e-commerce entities, and C is the e-commerce application service center.

The PASCAL-like description of the whole data flow of the e-commerce infrastructure is shown as follows:

Program Basic_Architecture //statement of sub-process and function; Procedure Send_To(Message_Sender,Message_Receiver,Message); //authenticated

entity sends information; Procedure Show_Message(Message˖String)˗//display system prompts information; Procedure Process_Terminated(); //authentication error, system exits

abnormally; Procedure Process_Finished(); //authentication completes, and system exits

normally; Function Find_Entity(Request): Entity; //search for the e-commerce entity

meeting the requirement; Function Is_Transaction(Requst_SenderˈRequest_ReceiverˈRequest)˖Boolean˗

// judge whether to process the e-commerce trade; Function Start_Payment(): Boolean; //start payment subsystem, and return

a Boolean variable; //The main body of e-commerce infrastructure flow Begin

Send_To(A,C,Request); //A sends business request to C; //C startsup search engine to find an appropriate e-commerce entity B; start:B:=Find_Entity(Request)˗

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Send_To(C,B,Request); //C transmits the request to B; If (Is_Transaction(A,B,Request))Then

Begin Send_To(B,A,Response); //B sends the response information; If (Start_Payment()) Then Begin Show_Message("The e-commerce process completes")˗ Process_Finished()˗ End Else

Begin Show_Message("Payment subsystem Error")˗ Goto start˗ End˗ End Else Goto start˗ End

Figure 8.2 Data flow of e-commerce infrastructure

8 E-commerce Architecture and System Design

The security and payment subsystem in the e-commerce infrastructure of data flow and PASCAL-like description are both simplified. The security sub-system is included in the whole infrastructure, rather than a very independent module, so it is not explicitly represented here; as a more complete sub-module, the payment subsystem is not detailed, and we just describe its location in the system and interfaces to the internal and external applications of the system, and its internal structure will be detailed in the following part.

8.1.3 Process Control of Infrastructure

The process control of e-commerce infrastructure can be divided into the following parts:

1. A sends a business request to C

There is an Intranet built in the internal structure of e-commerce entity A, the Intranet is connected with the Internet through firewall. If e-commerce entity A has a trade request, the request information is encapsulated according to the specified protocol format (here is M1), and sent to the e-commerce application system through firewall system, then the e-commerce application handling module does the following work, whose Petri net model is shown as Fig. 8.3.

Figure 8.3 Process of A sending a business request to C

Position P1 has a token in the Petri net model in the above figure, which represents A has an e-commerce request, making transition T1 in the enabled state; there is no token at other positions, so the corresponding transitions do not meet the conditions of Enable and are in the waiting state. Information M1 whose

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format could be represented as (A, C, T1, Request) is an encapsulated information package generated according to the information interaction protocol between the e-commerce application system and the e-commerce entities, and it can be represented as; T1 represents that the e-commerce entity A sends business request to the e-commerce entity C.

It is clear that only one element P1 is in the preceding set {·T1}of T1 from the Petri net principium, and m (P1)ıW (P1, T1), that is the transition t1 meets the triggering condition, and could be triggered at any time and can cause the change of the system state of the Petri net.

2. C accepts A’s Request, and prepares to start agent to search the appropriate entity B

The result of the triggering of T1 is that A sends information package M1 to C, and the e-commerce application system C accepts M1 , sends response information to A, and at the same time prepares to start several intelligent agents to search the e-commerce entity B that meets the request, that is position P2. When T1 is triggered, the Petri net model is shown as Fig. 8.4.

Figure 8.4 Entity C accepts A’s request Based on the rules of Petri net model transition trigger, the triggering of T1 in

the Fig. 8.3 turns the Petri net of e-commerce infrastructure into Fig. 8.4, in which position P2 owns one token, P1 loses the token, and T1 completes the triggering. The token of P2 means that transitions T2 and T5 could be triggered, that is C sends the response signal to A, and prepares to start intelligent agent to search the appropriate entity B at the same time. When the only forward element of transitions T2 and T5 owns a token, the triggers of these two transitions could complete in parallel, without the conflict problem.

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3. C sends a response to A, and starts an agent to search the appropriate entity

B at the same time

The trigger of transition T5 is natural, and position P4 obtains the token, which represents entity A receives the response information from e-commerce application system C, and waits patiently for the appropriate trading e-commerce entity B; see Fig. 8.5.

Figure 8.5 Find no appropriate entity B The trigger of transition T2 is little complicated, because transition T2 is a

condition judgment transition, which may lead to two different possible results. (1) Find an appropriate entity B The several intelligent agents started by the application system C find B that

meets A’s Request, and the Petri net model of e-commerce infrastructure is omitted here. The position P2 loses the token, and the position P3 obtains the token at the same time. A token in P3 means that entity B will decide whether to trade with A based on the specific information of A’s Request.

(2) Not find an appropriate entity B The transition T2 is triggered, but the appropriate entity B is not found

(namely failed), then position P2 loses the token, and position P8 obtains the token. P8 with token means one’s attempting to find an appropriate entity B failed, and transition T6 obtains the triggering condition. T6 is actually a process of handling error, and triggered T6 causes P1 and P9 to gain a token. If P8 receives a token, the system will restore to initial state, and A sends Request to C again. At this time, A can adjust original request according to response information, and encapsulate it into M1 again to send it to C; P9 is a counter, when tokens contained in P9 exceeds pre-established capacity limit, transition T7 is triggered, P7 gains a token, causes an error in the system and exits, then the whole system stops. B makes decision on whether to trade with A.

Entity B will decide whether to trade with A based on the Request sent by A.

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(1) E-commerce trading process If B accept A’s Request, T3 will obtain a positive trigger (that is success), and

sends a response information package M2 to A. The format of M2 is: (A, C, T1, Response). The Petri net model of the infrastructure is shown as Fig. 8.6.

Figure 8.6 Entity B accepts request

Then P4 and P5 both have tokens in the preceding set of transition T4, and T4 meets the trigger condition, which could trigger T4 to start the payment process and complete an e-commerce trade.

(2) Do not make e-commerce trade If B cannot meet the business Request of A, T3 gets negative trigger (that is

fail). Position P3 loses the token, and P2 gets the token and the whole Petri net model returns to the similar situation of step 2 (omitted).

After analyzing the business Request of A, and if B cannot meet A’s request, the system will give up trying to trade further. Then P2 gets a token, and can search again for the e-commerce entity meeting request, or can generate an information package to A based on the response information from B, promoting A to adjust its business request appropriately to better realize e-commerce interaction.

4. Start payment process

Both P4 and P5 own tokens, that means e-commerce entity A has a business request and entity B can meet A’s business request, transition T4 is triggered, and then the e-commerce payment process starts. However, because of the complexity of the payment protocol, the payment process is actually possible to fail, so it’s necessary to consider the following two points:

(1) The payment process succeeds, and the e-commerce interaction completes If the payment subsystem runs well, the Petri net model of the infrastructure

evolves to Fig. 8.7.

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Figure 8.7 The completion of payment process The transition T4 is positively triggered, and P6 obtains a token, which indicated

the e-commerce interaction completes normally.

(2) The payment process fails, and the e-commerce interaction could not be completed If errors appear in the running process of the payment subsystem, the evolvement of the Petri net model could also be presented with the corresponding Petri net (omitted). Then the transition T4 is negatively triggered (namely fail), and P7 obtains a token, indicating the e-commerce interaction is abnormally stopped.

The above figure is just a sketch Petri net model of the e-commerce infrastructure. Conceptually and in detail analyzed the data flow of the e-commerce infrastructure, displayed the hidden control flow and information flow in the data flow on the view of the process control. However, it is emphasized that the model is just a concept model, not an exact model of modern e-commerce architecture; meanwhile, the security subsystem and payment subsystem are not detailed in the model analyzing process, and are left in the following chapters, which simplifies the complexity of the e-commerce infrastructure from the layered point of view.

8.1.4 Optimizing Method of Infrastructure

The optimizing process of e-commerce infrastructure needs to be constructed in terms of the following optimizing rules:

1. Reachability

When designing a distributed system, there is a very important problem: Whether the system could reach a certain specified state, or complete a certain specified functional behavior. To prove that whether a model system could reach the

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specified state through a certain functional behavior, designers need to find a chain generated by transition trigger. The system can reach the specified state

m along the transitional activating chain from the initial state i m and the chain 0 , represents a series of functional behavior.

It’s necessary to point out that, in a system model based on Petri net, the

reachability of a specified state m is defined by a transitional activating chain i which can be followed from the initial state m to the specified state 0 m . If there i is only one transition in the transitional activating chain from m to 0 m, i m is i called instant reachable state.

2. Boundedness

The position is usually used for representing an information storage unit in communication and computer system, so designers must identify whether a particular control strategy could lead to overflow of the information storage units. The concept of bounded is introduced into the system model based on Petri net to handle the overflow problem of information storage unit. A k-bounded position p means the total of tokens must be less or equal to k in the changing process of the

system states ( m 0 m i ) . If all of the positions in a Petri net model are k-bounded, the Petri net model is called k-bounded.

3. Conservativeness

In a real system, the quantity of available resource is usually limited because of various factors, such as the economic ones. If a token is used to represent resource, the quantity of tokens in a system is usually conservative, that is however the state of the system changes, the quantity of the tokens in the Petri net model of the system is always unchangeable. If a single host computer in the network fails, the number of tokens representing the host resource should decrease one.

The conservativeness of a Petri net is defined as: a vector w ( ww 1 , 2 , " , w n ) is existed, n is the position number, the weight of each position in the model is greater than zero ( p PWp , () ! 0), and the sum of weights of tokens keeps unchanged in the changing process of the system state. Figure 8.8 represents a conservative system model:

Figure 8.8 Conservative petri net model Here w (1, 1, 2, 1, 1), thus the sum of weights of tokens is always 2. A Petri

net model whose sum of tokens is always equal to 1 is a restricted conservative model.

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4. Activity

The concept of activity is tightly connected with deadlock, and deadlock is thoroughly discussed in the computer OS principle. To avoid deadlock, a Petri net model must exclude the following four cases:

ķ Resource monopolized ĸ Keep waiting Ĺ Non- deprivation ĺ Form waiting circle

5. Resumption

An important problem in the model analysis based on Petri net is whether a system has error-resuming function; that is to say the system can self-resume from an error state to a correct state. As to Petri net model, Resumption means

that, if the initial state s can reach a certain state 0 s along the transitional i activating chain, there must be a transitional activating chain from s to i s 0 .

6. Common optimizing models

We can use the following common optimizing models in the optimizing process of e-commerce infrastructure (Figs. 8.9

Figure 8.9 Optimizing models 1 Figure 8.10 Optimizing models 2

Figure 8.11 Optimizing models 3 Figure 8.12 Optimizing models 4

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Figure 8.13 Optimizing models 5 Figure 8.14 Optimizing models 6

The optimizing work of e-commerce infrastructure would be greatly simplified with the above six common optimizing models.

8.1.5 Event Process Control of Infrastructure

In the e-commerce infrastructure, most events are represented as various transitional activating conditions that are event drivers. Generally, several forms mainly for the process control of e-commerce system events are as follows:

1. Sequential relation

If the occurrence of E1 is the condition of E2’s occurrence, E1 has sequential relation with E2, this situation is shown in Fig. 8.15.

2. Conflict relation

If E1 and E2 cannot occur concurrently, E1 and E2 are conflict mutually. This situation is shown in Fig. 8.16.

Figure 8.15 Sequentially occurrence Figure 8.16 E1 and E2 are mutual of E1 and E2

exclusive

3. Collision relation

If occurrence of E1 or E2 can result in the change of certain position state, we define that the position has collision with E1 and E2, as shown in Fig. 8.17.

Collision refers to the relation that both parts have occurrence right, but only one could occur. As to the system itself, it’s uncertain that who has the priority. It needs the system environment to give some hints by inputting one bit of information

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to decide which of two conflict parts occurs first. Therefore, collision is also called choice or non-determinism, or we can say it needs decision.

The characters of the competing resources between conflict and collision are different: one competes for information, and the other competes for space to store information; the competitive result is also different: whichever occurs in conflict, the other will lose occurrence right; however whichever occurs in collision, the existence of the other will always cause collision with b. Collision reflects the potential danger.

4. Concurrent relation

If E1 occurs before E2, the system could reach a certain state. If E1 and E2 occur concurrently, it also could reach the same state, and there is no conflict, which means E1 and E2 have concurrent relation. Concurrency defined here is just involved with two events in the assumption without collision, as shown as Fig. 8.18.

Figure 8.17 E1 and E2 are in collision Figure 8.18 E1 and E2 are mutually mutually

concurrent

It is not necessary that E1 and E2 must occur concurrently, namely one-step occur, and it is not even guaranteed that the event having occurrence right must occur. If E2 occurs before E1 as in Fig. 8.18, E3 gets occur right, and E1 and E3 are in the conflict state of competing resource. If E3 occurs in further to resolve the conflict, E1 will lose one-step occurrence right.

If E1 occurs in conflict of E1 and E3, B5 gets the token, and the system reach the final state {B3, B5}. Another possibility from the initial state {B1, B2} to {B3, B5} is that E1 occur first, and then E2 occurs. The concurrence of E1 and E2 can also reach the same state. The two cases will not cause conflict.

Where the system conflict occurs is the system control occurs. If confusion occurs in the application system, the system environment cannot determine whether conflict occurs, or the conflict has disappeared without control. In a word, the occurrence of confusion will bring trouble to system analysis and control, and the system model with confusion is not a good model. The reason for the occurrence of the confusion is that the system and system environment are divided incorrectly. In other words, some transitional extension in the system is

Introduction to E-commerce

uncompleted, and their extension should be supplemented from the environment to obtain more integrated and more exact description of these transitions.