BaaS - Binding as a Service

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BaaS is a tool that helps you implement a web service composition framework. One important step in dynamic web service composition is the binding of concrete web services to the activities involved in the composition. BaaS provides this functionality as a service.

Service binding is a complex task, which poses some significant challenges. For each task in the abstract composition model associated with a composite service, there are usually several web services offering the required functionality. However, they may differ in non-functional properties such as reliability, cost, or response time. Therefore, the quality of service (QoS) is the deciding factor in choosing which concrete web service to bind to each task.

In order to make a qualitative comparison of service compositions, it is necessary to estimate the QoS of a composite service based on the QoS of its component services. For this purpose, BaaS uses the QoS extension for BPStruct, which can compute the aggregated QoS values for composite services with complex structures.

Comparing composite services characterized by multiple QoS attributes is not a trivial task, because there is usually no solution that simultaneously optimizes all attributes. BaaS allows its clients to express trade-offs between different QoS parameters, by using the QoSPref approach.

A presentation of BaaS can be found in this paper.

System Requirements

Windows XP/Vista/7/8
a 32 bit JRE or JDK installation. (You need a 32-bit installation even on a 64-bit machine. BaaS uses the QoS4BPStruct library, which loads a native library compiled only for 32-bit Windows platforms.)

Installation

Download and unzip the binaries. This will create a directory called baas-1.0, which we will refer to as <BAAS_HOME>.

Open the file <BAAS_HOME>\bin\_settings.bat in a text editor and:

edit JAVA_HOME to point to your 32-bit java installation directory.
edit BAAS_PORT, if you are not happy with the default value (9090) of the port used by the BaaS server.

Quick start

Open a command line window, go to the directory <BAAS_HOME>\bin and type:

startBaas

Open another command line window, go to the directory <BAAS_HOME>\bin and type:

client ..\config\test1.properties

Congratulations! You have successfully sent a binding request to the BaaS server. Now it's time to take a closer look at the scripts in the <BAAS_HOME>\bin directory.

startBaaS.bat

Starts the Baas server on the port configured in _settings.bat. Assuming that the default port 9090 is used, the service will be available at http://localhost:9090/baas.

client.bat

Sends a binding request to the BaaS server. It takes as argument the path to a configuration file containing the following information about the request to be sent:

the list of QoS attributes (name and aggregation type)
the QoS constraints
the QoS preferences
for each task in the abstract composition model, the QoS values of the concrete web services offering the required functionality
the abstract composition model

Usage example:

client ..\config\test1.properties

In the configuration file, the abstract composition model is specified by means of two properties:

the path to a file from which the abstract composition model can be extracted
the format of the data contained in this file

Two formats are currently supported: xml and bpmn. The xml format is a BaaS-specific representation of the abstract composition model. The bpmn format is a business process representation conforming to the OMG specifications.

The file ..\config\test1.properties in the usage example above specifies an xml representation of the abstract composition model. You can experiment with a bpmn format by opening the file <BAAS_HOME>\config\test1.properties in a text editor and replacing the lines:

workflow.path = ../example/example1.xml
workflow.type = xml

with the lines:

workflow.path = ../example/example1.bpmn
workflow.type = bpmn

performanceClient.bat

Generates and sends a batch of binding requests to the BaaS server. It takes two arguments:

the path to a directory containing workflows (abstract composition models in the xml format)
the path to a configuration file controlling the generation of binding requests

The configuration file contains the following information:

the list of QoS attributes (name and aggregation type)
the QoS constraints
the QoS preferences
the range of component services to be generated for each task of an abstract composition model
the range of values for each QoS attribute

Usage example:

performanceClient ..\workflows ..\config\perftest1\config.properties

performanceTest.bat

Generates a batch of binding requests for which the best solution is computed. Instead of sending the requests to the BaaS server, it directly calls the solver. The script takes two arguments:

the path to a directory containing workflows (abstract composition models in the xml format)
the path to a configuration directory

The configuration directory must contain three files:

config.properties, having the same structure as the configuration file needed by the performanceClient script
run.properties, used to configure the number of runs for each workflow and the parameters of the solver
logback.xml, used to configure the logging settings

Usage example:

performanceTest ..\workflows ..\config\perftest1

oryxModelToWorkflow.bat

Converts files from the bpmn format to the BaaS-specific xml format. Several bpmn models created with the Oryx Editor are provided in the directory <BAAS_HOME>\models\oryx. The script takes two arguments:

the path to a directory containing files in the bpmn format
the directory in which the converted workflows should be stored

Usage example:

oryxModelToWorkflow ..\models\oryx ..\tmp-workflows

bitModelToWorkflow.bat

Converts files in the XML format used by IBM WebSphere Business Modeler to the BaaS-specific xml format. Several files in this format taken from the IBM Bit process library are provided in the directory <BAAS_HOME>\models\bit. The script takes two arguments:

the path to a directory containing files in the XML format used by IBM WebSphere Business Modeler
the directory in which the converted workflows should be stored

Usage example:

bitModelToWorkflow ..\models\bit ..\tmp-workflows

workflowPicker.bat

From the workflows available in a given directory, selects those being sound and (optionally) satisfying some constraints related to the number of tasks in the abstract composition model.The script takes the following arguments:

-inputDir <path>: the path to a directory containing workflows in the BaaS-specific xml format
-outputDir <path>: the directory in which the selected workflows should be stored
-minTaskCount <number> (optional argument): the minimum number of tasks of the selected workflows
-maxTaskCount <number> (optional argument): the maximum number of tasks of the selected workflows

Usage example:

workflowPicker -inputDir ..\tmp-workflows -outputDir ..\picked-workflows -minTaskCount 5

Building BaaS from sources

The BaaS source code is managed with Git. If not already available, install git from here.
Open a command line window, go to a directory of your choice and type:
```
git clone git://git.code.sf.net/p/baas/code baas
```
This command will create a directory called baas, in which it will place a clone of the git repository. In the baas directory you will find a subdirectory called projects. From here on, the projects subdirectory will be referred as <BAAS_PROJ>.
If not already available, install a 32 bit JDK. You need a 32-bit JDK even on a 64-bit machine. BaaS uses the QoS4BPStruct library, which loads a native library compiled only for 32-bit Windows platforms.
Open <BAAS_PROJ>\gradlew.env in a text editor and set JAVA_HOME to point to your 32-bit JDK.
Edit the value of baasPort in <BAAS_PROJ>\gradle.properties.
Open a command line window, go to the <BAAS_PROJ> directory and type:
```
gradlew assemble
```

BaaS-specific gradle tasks

Open a command line window, go to the <BAAS_PROJ> directory and type:

gradlew tasks

This will display a list of available gradle tasks. Some of these tasks are BaaS-specific and are shortly presented in the paragraphs below.

runBaaS

Starts the Baas server on http://localhost:9090/baas (port value can be configured in <BAAS_PROJ>\gradle.properties).

Usage example: open a command line window, go to the <BAAS_PROJ> directory and type:
```
gradlew runBaaS
```
runClient

Starts the client program that sends a binding request to the BaaS server.

Usage example: open a command line window, go to the <BAAS_PROJ> directory and type:
```
gradlew runClient -PconfigFile=src/dist/config/test1.properties
```
runPerformanceClient

Starts the performance client program that sends a batch of binding requests to the BaaS server.

Usage example: open a command line window, go to the <BAAS_PROJ> directory and type (on a single line):
```
gradlew runPerformanceClient -PworkflowsDir=../experiment/src/dist/workflows
                             -PconfigFile=../experiment/src/dist/config/perftest1/config.properties
```
distZip

Creates the binary distribution zip: <BAAS_PROJ>\build\distributions\baas-1.0.zip

Usage example: open a command line window, go to the <BAAS_PROJ> directory and type:
```
gradlew distZip
```

Eclipse configuration

Install a recent version of Eclipse (Kepler or Juno recommended).
Configure your 32-bit JDK as standard JRE for Eclipse:
Install the Dynamic Languages Toolkit Core plugin from http://download.eclipse.org/releases/indigo:
Install the ANTLRv3 eclipse plugin from http://antlrv3ide.sourceforge.net/updates:
If not already available, download and install ANTLRv3.

In Eclipse, configure the ANTLR package as shown in the image below:
In order to generate the Eclipse project files for BaaS, open a command line window, go to the <BAAS_PROJ> directory and type:
```
gradlew eclipse
```
In Eclipse, import all projects found in the directory <BAAS_PROJ>