XRX

The Implementation Process under XRX Architecture

Cristina Nemeş, Marius Podean and Lucia Rusu

Faculty of Economics and Business Administration, Babeş-Bolyai University, Cluj-Napoca, Romania

Keywords: Data model, XML, XPath, XQuery, XRX, XSLT.

Abstract: The XRX (XForms - REST - XQuery) architecture is a three tier architecture which uses at each tier data in

XML format. This offers a great advantage because data is not being transformed in different other formats

in order to communicate with other layers. Using this architecture the application becomes more agile,

flexible and simple because there is no need of translations like in the classical architecture. This paper

describes the implementation process of an application developed under the XRX architecture using W3C

standards (XHTML, XML, XPath, XQuery, XSLT, XForms), REST interfaces and a native XML database.

1 INTRODUCTION

Nowadays every company works with databases and

has to constantly improve the way they manage their

data in order to facilitate CRUDS operations

(Create, Read, Update, Delete, Search) on the

database. Many software developers have

implemented in relational databases the possibility

to save data in XML (eXtensible Markup Language)

format.

Databases represent a very important aspect in

web applications because the exchange of data and

documents inside a company and between

companies is essential. To remain competitive on the

market companies have to improve their way of

exchanging data. Organizations have to exchange

data and complex documents in the same format in

order to be understood by other partners.

Collaboration is an important process implemented

by many companies in order to achieve common

goals. An important issue is to ensure the exchange

of complex documents between companies in a way

that is software independent in order to facilitate the

process of collaboration between organizations.

This paper presents a model that integrates these

issues and brings some solutions. The paper presents

a way of developing web applications under a new

architecture called XRX. This architecture works

with data in XML format at each tier unlike the

classical architecture where data is stored in

different formats. The aim of this paper is to make a

comparison between the XRX architecture and the

classical architecture and to emphasize the

advantages of the XRX architecture. In order to

achieve this goal we have implemented a web

application according to XRX architecture.

A new idea for developing and implementing

Web applications is based on W3C standards and

REST interfaces. The W3C standards used are data

format (XML, HTML, XHTML), programming

languages (XQuery, XPath, XSLT), and schema

(XML Schema) (Kaufmann and Kossmann, 2009).

More and more web applications are developed

using RESTful Web services because the complexity

of developing applications that involve Web services

access, data processing, and human interaction are

reduced (Onose et al., 2009, Selonen et al., 2010).

XML is a language used especially on the WEB

because it facilitates the exchange of data between

applications which run on different platforms and

are developed with different technologies. To

provide the same data format we use a XML

vocabulary called UBL (Universal Business

Language) (Bosak and McGrath, 2006) which is a

standard for economic documents like orders,

products catalogs and invoices.

In section 2 we present the collaboration concept,

and in section 3 we provide a brief overview on the

XML stack of languages used for implementing the

application and XRX architecture. The application is

described in section 4. Section 5 presents related

works. In section 6 are presented conclusions and

future work.

103

Neme¸s C., Podean M. and Rusu L..

XRX - The Implementation Process under XRX Architecture.

DOI: 10.5220/0003931101030109

In Proceedings of the 8th International Conference on Web Information Systems and Technologies (WEBIST-2012), pages 103-109

ISBN: 978-989-8565-08-2

 2012 SCITEPRESS (Science and Technology Publications, Lda.)

2 COLLABORATION

The process of collaboration has emerged due to the

need of communication between companies.

Collaboration is a process in which entities share

information, resources and responsibilities to

achieve a plan, implement and evaluate a program of

activities to achieve the same goal (Camarinha-

Matos and Afsarmanesh, 2008). In order to

collaborate, organizations have to exchange data and

documents in the same format in order to be

understood by other partners. To work,

organizations need a common language that will

enable the implementation process with minimal

effort.

In terms of computing, collaboration is the

integration of different technologies into a single

platform in order to improve the performance of data

and complex documents exchange. The model for

the common language in our case is UBL which is

based on XML. UBL is used in order to create

complex documents that have the same format so

that organizations that use the same standard can

easily exchange data.

UBL is the language used in order to implement

the process of collaboration in our application. In the

following section we describe the XRX architecture

and the W3C standards used in order to develop the

application.

3 XML FAMILY AND XRX

ARCHITECTURE

This section presents the key elements of the XML

stack of languages and the XRX architecture used in

the implementation process.

XRX is a "no-translation" (McCreary, 2010) web

application architecture based on three technologies

(McCreary, 2008):

- XForms on the client;

- REST interfaces;

- XQuery on the server.

According to (McCreary, 2007) this architecture

gives web developers a tenfold increase in

productivity.

XForms is an XML application that separates

content from presentation. After (Boyer, 2007)

XForms is not a document type to be used

independently so it has to be used with XHTML or

SVG, and (Turner and Windauer, 2010) states that

XForms will become the next generation of forms

for World Wide Web. XForms is based on the MVC

(Model-View-Controller) architecture and is

compatible with other W3C standards like CSS,

XPath, XQuery, XML Schema. More and more

companies (Semanta, Volkswagen Financial

Services, Australian Bureau of Statistics, Teleflex,

Manugistics) want to enjoy the XForms benefits so

they are collaborating with Orbeon in order to obtain

very efficient forms (Orbeon, 2012).

REST is a lightweight alternative to mechanisms

like RPC (Remote Procedure Calls) and Web

Services (SOAP, WSDL). Many websites like

Twitter, Yahoo, Flicker, Vimeo, PhotoBucket,

LinkedIn, Amazon S3 use the REST protocol due to

its great characteristics. (Fielding, 2000) defines

REST as a set of architectural constraints that

emphasizes scalability of component interactions,

generality of interfaces, independent deployment of

components and enforces security.

XQuery is a query language which allows to

select information according to one or more criteria,

joining data from multiple documents, mathematical

operations on numeric data type (Walmsle, 2007).

Instead of using XQuery we can use XSLT. XSLT

(Clark, 1999) is a declarative language used to

transform XML documents into text, HTML or

XML. An XSLT stylesheet describes the rules that

transform a source tree into a result tree. XSLT uses

XPath expressions to select the source nodes from

the trees. XSLT is used in general for the

presentation of data, while XQuery is much more for

making queries and working with data. XSLT can be

used instead of XQuery but the code is not so

compact like with XQuery.

XML is a technology used to represent data and

documents. By using XML technologies, a high

portability of documents can be obtained (Bray et

al., 2008). XML allows to define vocabularies that

describe data according to an activity domain in

order to facilitate the exchange of documents

between business partners from the same area. UBL

is a synthesis of existing XML B2B languages

(RosettaNet, cXML, xCBL) that is interoperable

with EDI systems. It can be applied in different

domains like administration, electronic trade.

All these languages are used in the

implementation process described in the next

section.

4 APPLICATION

XRX architecture is a new three tier architecture

which offers the possibility to develop complex

applications. This architecture can very easily be

combined with the MVC (Model-View-Controller)

pattern. In our case the Model is stored in the eXist

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Figure 1: XRX architecture and traditional architecture.

database, the View is generated automatically from

XForms elements and the Controller part can be

implemented in XQuery/XSLT/XProc or as a

combination between these technologies.

4.1 Application Architecture

The application developed under the XRX

architecture uses at each tier W3C standards, that

work with data in XML format (Figure 1).

In this architecture there are no translations

between the languages used at each tier because all

work with data in XML format. On the other hand in

the classical three tier architecture which uses

HTML in the browser, Java/C#/PHP at the business

logic tier and SQL databases there are needed four

types of translations (McCreary, 2010):

- HTML to objects;

- objects to SQL;

- SQL to objects;

- objects to HTML.

To develop an application under the classical

architecture is required hard work to construct, test

and maintain the application, and (Davis and

Maguire, 2011) calls the complex set of

transformation "non-value-added transformations".

The XRX architecture is called a “Zero Translation”

(McCreary, 2010) architecture because there is no

need for transformations between the tiers.

On the presentation tier, which can be seen as the

View in the MVC pattern, we use XHTML and

XForms in order to display the graphical interface to

the user in the browser instead of the classical

HTML forms. XForms is very effective in

processing sets of complex semi-structured data. In

the classical applications JavaScript is used to make

validations on the client, to communicate with the

server and also to make some calculations.

JavaScript is an object oriented language which has

a syntax influenced by that of C (Goodman, 2001).

For very complex and dynamic user interfaces

XForms can be extended with JavaScript. We use

XForms instead of JavaScript in order to process

complex datasets, to make validations on the client,

calculations and constraints. A very important

advantage of XForms is that it processes very well

documents in different formats. Working with

JavaScript for processing and manipulating

documents in XML format requires many lines of

code for inserting, deleting and making some

changes in the XML trees. In Figure 2 is presented

an extract from a JavaScript function which creates

an XML tree using DOM methods.

At the business logic tier we use XQuery and

XPath to manage data in XML format instead of

PHP, Ruby or object oriented languages like Java

and C#. In (Costello, 2008) a problem is solved in

two ways: using XSLT and using Java. The result of

his experiment was that the problem was solved with

XSLT in 10 lines of code and over 100 lines in Java.

In Figure 3 and 4 we present the code for

transforming the order in order-response using an

XSLT stylesheet. These figures show that is much

more easier and simple to implement this

transformation using XQuery instead of PHP.

In a classical architecture at the data tier is used

SQL to manage data stored in relational databases.

We use XQuery to manage data stored in XML

format in the eXist database, which is a native XML

database. Relational databases contain tables where

data is stored as records. A native XML database

contains collections of XML documents.

XML

PRESENTATION TIER

XHTML+XForms

BUSINESS LOGIC TIER

XQuer

+ XPath + XForms

DATA TIER

XQuer

Native XML Database

HTML

object

relational

ecification

PRESENTATION TIER

HTML/XHTML

BUSINESS LOGIC TIER

Java/C#/PHP/Rub

DATA TIER

SQL

Relational Database

XRX-TheImplementationProcessunderXRXArchitecture

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Figure 2: Creating a XML document using JavaScript.

Figure 3: Transforming an XML document with XQuery.

Figure 4: Transforming an XML document with PHP.

4.2 Application Description

In this section we describe the application explaining

the content and how the user has to interact with it.

Our application implements the exchange of

economic documents in electronic format between

different companies. The application is composed of

a wizard which represents the order and two

documents: order response and the invoice.

On the first page of the wizard presented in

Figure 5 are displayed the products from which the

client may choose. The client has to activate the

"Add" button corresponding to the desired product.

When the button is pushed below the list of products

appear the selected one with the implicit quantity 1.

The quantity can be changed by typing another, and

in order to remove a selected product the customer

has to type “0” in the quantity field.

On the second page are displayed in a table

details about the customer like full name, address,

work-address, e-mail.

On page three presented in Figure 6 the customer

selects the delivery address. The customer has to

select a radio button which corresponds to the

desired delivery address. Also the customer can add

Figure 5: First page of the wizard.

Figure 6: Selecting the delivery address.

a new address, and the page is dynamically updated

(appears a new radio button for the new address).

The same process applies when choosing the

method of payment except that the client cannot

introduce a new payment mean.

To choose the delivery date the client has to

choose the date using a date picker.

The last page of the wizard presents a table of

selected products that the client wants to order. Are

displayed the product ID, name, quantity, price and

are calculated the value of the products (price *

quantity) and the VAT (value of products * percent

VAT). Finally, is calculated the total amount of the

order as the sum of value of goods and VAT .

At the final step the buyer has to push the

"Submit" button to send the order. If the order has

been submitted successfully the seller receives an

order response that specifies if the order is accepted

or not. If the order has been accepted the buyer will

receive an invoice for the purchased goods.

Each step in the wizard is mandatory. If a

customer does not complete a step or the introduced

data is invalid the customer receives an information

message. For example Figure 7 presents a message

validation informing the user that the selected

delivery date is invalid because it must be greater

than the start date which is the current date or the

date of the order. If a client fails to complete one or

more steps in the wizard when the "Submit" button

is pressed to send the order, the order will not be

sent (Figure 8).

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In this section we presented the interaction of the

user with the application by describing each step of

the wizard. In the next section we present the

implementation process.

4.3 The Implementation Process

In this section we present the implementation

process for our web application developed under the

XRX architecture. This application works with data

in XML format in order to improve the exchange of

information between partners according to the UBL

standard.

The application is implemented under the XRX

architecture and also according to the MVC design

pattern. The model contains the data values, the

view is represented by the screen presentation and

the controller defines the way the user interface

reacts to user input (Gamma, 2009). MVC can use

other design patterns like Decorator to add scrolling

to a view or Factory Method in order to specify the

default controller class for a view (Gamma, 2009).

The model is composed of the XML documents

stored in the eXist database. The XML documents in

the database are validated according to the UBL

standard.

The view represents the user interface which is

composed of XForms elements and XHTML. The

view is the wizard and the two documents: order

response and invoice. The wizard is generated

dynamically from a query. Also the documents are

generated dynamically from an XQuery code using

different eXist specific functions in order to save the

data completed by the user in the database, and

make the XSLT transformations from order in order

response, and then from order response in invoice.

The wizard is created using a switch-case

structure where each case represents a page/step of

the ordering wizard. The client has the possibility to

navigate back and forward to make some changes

using "Back" and "Next" buttons which appear on

each page of the wizard. To implement a button we

use the trigger element. A trigger is an abstraction of

a web button that allows forms to be more portable.

To choose the delivery date we created an input type

element that allows the customer to choose a date.

Because through a bind element we specified the

type of this element as type = "xs:date" at a simple

click in this box appears a calendar that allows the

user to choose the date (date picker).

The controller part is composed of the XQuery

documents that generate the wizard and use the

eXist specific functions to save the customers data

in the database, and to make the XSLT

Figure 7: Delivery date validation.

Figure 8: Error validation in the wizard.

transformations.

We have created a module where we have

implemented the necessary functions that generate

the wizard. The function businessrules presented in

Figure 10 gets all the child elements from the

"bind.xml" document. In this document are

implemented the bind XForms elements. The

function products selects all the "cac:OrderLine"

elements from the "products.xml" document. This

function selects all the products stored in the xml

document.

In the classical architecture instead of XQuery is

used PHP, Java, or other languages. When working

with PHP in general is used a relational database like

MySQL. Making a comparison between the code for

extracting the data using XQuery and using PHP we

can say that using XQuery is more efficient and

simple than using PHP.

According to (McCreary, 2008) the number of

code lines when using XQuery is much smaller than

the number of lines of code when using SQL and

Java.

(Candillon, 2011) presents a comparison that

shows the amount of code lines needed to develop

the same application using different technologies

like Java, PHP and XQuery. The charts present that

using XQuery the number of lines of code can be

Figure 9: Back and Next buttons.

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Figure 10: Function businessrules.

reduced up to 80% if we refer to Java or with 62% if

we refer to PHP (Figure 11).

The PubZone application was implemented in

Java and in XQuery. The XQuery implementation

ended up to be more compact and elegant than the

version in Java (Kaufmann and Kossmann, 2009,

Candillon, 2011) (Figure 12).

In order to develop complex web applications

using the XRX architecture is needed only one

person who can do the work of ten people

(McCreary, 2010). When developing an application

under a different architecture many persons are

needed in order to implement the application using

different technologies. Thus the costs of developing

an application using the XRX architecture are

smaller than in the case of other type of architecture

(McCreary, 2010).

5 RELATED WORK

Previous work in the field of REST like (Fielding,

2000) has a great impact on the applications that use

this architectural style. Also some important works

related to XML, REST and XQuery are (Kaufmann

and Kossmann, 2009) and (Davis and Maguire,

2011) which have developed applications using

XML technologies.

Regarding the XRX architecture the most

relevant and detailed explanations about this

architecture are given by (McCreary, 2007),

(McCreary, 2008) and (McCreary, 2010).

(Hunter, 2012) presentes the open source

"Corona" project which uses the MarkLogic Server

in order to manage and query XML and JSON using

REST. (Retter, 2012) presents a research regarding

the current approaches for invoking XQuery in a

RESTful manner over HTTP and the standardised

XQuery 3.0 annotations for REST. In (Couthures,

2012) and (Lenz, 2012) are presented different

approaches that are using XQuery and XSLT in

order to develop new applications.

6 CONCLUSIONS

The application presented is developed using XML,

XQuery, XSLT, XForms and UBL standard used to

Figure 11: Java vs. XQuery and PHP vs. XQuery

(Candillon, 2011).

Figure 12: Java vs. XQuery lines of code - PubZone

(Candillon, 2011).

represent economic documents in electronic format.

The application is built on three levels according to

the XRX architecture. This architecture replaces the

traditional three-tier architecture that uses HTML in

the browser, on the logical level languages such as

PHP, Ruby, C #, Java and SQL for relational

databases.

The comparison presented between the XRX

architecture and the classical architecture shows that

applications developed according to the XRX

architecture are more efficient and elegant.

Moreover the XRX architecture increases

productivity and reduces the implementation costs.

In our research one of the main goals was to develop

an application that can ensure a good exchange of

data between companies in order to facilitate the

process of collaboration.

In the future we plan to develop an application

following the same principles but using XProc

(XML Pipeline Language). XProc is a language used

to create pipelines which takes zero or more XML

documents as input and produces zero or more XML

documents as output. An important advantage of

XProc is that allows other technologies from the

XML stack of languages to interact ( XML Schema,

XInclude, XQuery, XSLT).

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