About the Data-Flow Complexity of Web Processes Jorge Cardoso Department of Computer Science, University of Madeira Funchal Portugal

Introduction Challenges for organizations Process design and management E-commerce applications E-business applications Managing Web services and Web processes Inherent problems of processes High complexity Low flexibility

Introduction High complexity bad understandability more errors and defects exceptions more time to develop, test, and maintain Flexibility Guiding principle in the design of business processes In most business processes, flexibility and complexity are related inversely. high complexity -> less flexibility it is more difficult to make changes to the process

Web process complexity The degree to which a process is difficult to Analyze, Understand, Explain It is characterized by Intricacy of activities’ interfaces Transitions Conditional and parallel branches The existence of loops Roles The types of data structures other process characteristics

Web process complexity Data-flow complexity Control-flow complexity Resources complexity Role complexity Etc…

Web Process Management Data-flow complexity analysis Used during process construction or reengineering Guarantee complexity and flexibility levels Complexity increase during reengineering may be the sign of a brittle, nonflexible or high-risk process. Give information concerning the cost and time to make changes to a process in order to make it more flexible. Processes evolve over time by modification A process can easily become fragile with age Use complexity analysis to assess the system’s condition

Web process data-flow Data-flow The flow of data between the Web services of a Web process Web service WSDL (Web Services Description Language) Major elements Input and output messages, data types, port types, and bindings. In our study of data-flow we are interested in messages and types.

Web processes BPEL4WS (Process Execution Language for Web Services) Describes the logic to control and coordinate Web services participating in a process flow Control flow (branch, loop, and parallel) Manipulation of data between Web services Faults and compensation.

Data-flow complexity Data-flow complexity increases with Complexity of data structures Number of formal parameters of Web services Mappings between Web services’ data Three individual metrics: Data complexity Interface complexity Interface integration complexity Dynamic in nature Static data aspects

Data Complexity WSDL Uses the XML Schema data type specification Primitive data types … Primitive data types

Data Complexity Research question What are the values of the various c i ? a) All the data types are primitive That they all have the same complexity i.e. c 1 = c 2 =…= c 19 b) Some primitive data types are more complex than others The primitive type ‘dateTime’ (c 7 ) is greater than the complexity of a ‘Date’ type (c 9 ), i.e. |c 7 |>|c 9 | Since the ‘Date’ type can be sought as the aggregation of ‘Date’ and ‘Time …

Data Complexity Primitive data types

Data Complexity Derived data types Defined in terms of other data types Derived by restriction, by list, and by union The XML Schema has 25 derived types build-in normalizedString, token, language, Name, ID, integer, unsignedByte, positiveInteger, etc Observation Derived data type must have a greater complexity than its base type Research Question How should we treat restrictions, lists, or unions? Is an extension more complex that a list or is the other way around? Derived data types

Data Complexity Derived data types

Data Complexity XML Schema Three compositor elements that allow constructing complex data types from simpler ones Sequence: A sequence defines a compound structure in which the data occur in order. Choice: The data within a choice are mutually exclusive. All: All defines an unordered group. Complex data types

Data Complexity … … … … Complex data types

Data Complexity Some research has already been carried out to study the complexity of data structures XML Schema introduces new elements Sequence, choice, and all Complex data types

Interface Complexity Each operation of a Web service has an interface An interface defines the input and output parameters of each operation Let us analyze the following WSDL specification:

Interface Complexity …

Interface Complexity A possible metric IC (Interface Complexity) to describe the complexity of Web service’s interface. IC = IE * PS IE is the Interface Entropy n is the distinct number of data types present in an interface p(i) the probability of the data type i.

Interface Complexity PS is the Parameters Structure The more parameters in an operation the more difficult is for the designer to remember all of them |o ip | is the number of parameters of the input structure |o op | is the number of parameters of output structure of operation o.

Interface Integration Complexity Interface integration complexity (ICC) Addresses the concept of coupling. Measures the interdependence of Web services operations, i.e. Web services operations connected with a transition to other Web services operations. BPEL4WS Data is passed between the different Web services using containers The messages held are those that have been received from Web services or are to be sent to Web services.

Interface Integration Complexity The higher the coupling between Web services, the more difficult it is for a designer to understand a given Web process

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