NEMUG Newsletter

June 2003, Articles

• Board Meetings
• Report on the May Business Meeting
• From The Chair
• May Meeting: XML, SOAP and Caché Web Services

Board Meetings

NEMUG Executive Board Meetings are open to anyone to attend. Your presence and views are welcome at any time. The meetings are held on the second Monday of even-numbered months, at the office of Henry Elliott in Wellesley. We try to get started at 6:00 pm. Dates for the next few meetings are:

• 6/9/03
• 8/11/03
• 10/13/03
• 12/8/03

If you are planning to attend, please let a board member know in advance, as we provide food and eat as we work, and need to be sure we have enough for everyone. The complete address for the meetings is:

Henry Elliott and Company Inc.
One Washington St. Suite 208
Wellesley, MA 02481

back to the top

From the Chair

In this issue's column, I am pleased to make three announcements:

• CHANGE OF LOCATION. Beginning with the September 9th meeting, we will hold our meetings at 93 Worcester Road in Wellesley. We think this will be an easier place to find, as it is right at the intersection of routes 95/128 and route 9. The Gateway Building is located at the northwest corner of the intersection, and is home to Partners Health Care Information Systems. For those of you who were at the meeting in January when Jeff Harrow spoke, this is the same location.
• HANDS-ON LEARNING. We plan to hold another Saturday School this fall, on November 1st. We are considering a couple of topics, and will present our ideas to you at the July meeting.
• JOHN GLASER to speak. As a kick-off to our new location, we are pleased to have John Glaser, CIO of Partners Health Care, be our featured speaker at the September meeting. For those of you who may not have heard him, John is an interesting speaker who can be both informative and enjoyable.

As always, we on the board are here to serve you, the members of NEMUG. Let us know what topics and speakers you'd like to hear at the meetings, and anything else that we can do to help further the knowledge and use of M.

Marilyn D. Paterno, Chair

May Business Meeting

Elections for the 2003-2004 year were conducted at the May 13th meeting. Those elected, whose names appear below, will begin their terms of office in July. The rest of the business meeting was postponed to the July meeting.

back to the top

May Meeting: XML, SOAP and Caché Web Services

Presenter: Bill McCormick, Manager of Applications Development Support at Intersystems

XML (eXtensible Markup Language) is a mark-up language exchanging data between applications, just as HTML is an Internet mark-up language for displaying data. The structure of XML is hierarchical and multidimensional, the same as the Caché database.

Adding %XML.Adaptor to a Caché class adds methods that enable the class to export data in XML format. This also enables the class to create either a DTD (Document Type Definition) or an XML Schema for the class which define the structure of the XML data. There are methods that allow you to output data to the principle device, to a 32k variable string or to a stream object.

Caché projects objects as XML documents using a XML projection. Object instances correspond to top level XML elements. The XML projection determines how object properties correspond to XML elements or attributes. Properties can be projected as an element (default), attribute, collection or not projected (none). XML elements are shown with start and end tags in a XML document (<NAME> Harry </NAME>). Attributes are shown as name-value pairs within an element with the value in quotes ( <CUSTOMER NAME="Harry"> </CUSTOMER>).

The %XML.Reader class works in conjunction with the methods provided by the %XML.Adaptor class. It allows you to read a XML document and create instances of XML enabled objects that correspond to the elements of the document. Data can be read from files, streams or line by line.

Web Services are a way of sharing application functionality over the Internet by using a collection of related methods that a client application can invoke using the SOAP (Simple Object Access Protocol). Web Services have a public interface described in WSDL (Web Service Definition Language) and they return an XML document formatted according to SOAP.

To create a Web Service add %SOAP.WebService to a Caché class. Within the class definition you define class methods (SOAP does not support invoking instance methods) that correspond to the methods of the Web Service. Each method has to have the keyword WebMethod in its definition. The Web Service class must define the following parameters:

• LOCATION - the URL for accessing the service ( http://localhost/csp/user/package.class.cls )
• NAMESPACE - Essentially a domain name ( http://isc.org )
• SERVICENAME - The name of the Service implementing this collection of Web Services.

When the Web Service class is compiled, Caché creates a SOAP interface for each method that converts a SOAP XML request into a specific call to the Web Method. Also, a WSDL document is created. The WSDL document is an XML document that lists the available methods with their signatures (parameters and types) for each Web Service. A SOAP client uses the WSDL document to determine which methods are available and how to invoke them. When invoked, the Web Method executes the method code and returns an XML response document to the SOAP client.

Web Methods can return arrays of objects by defining a class query, a result set based on either a SQL statement or user defined code.

Caché also has limited support for SOAP clients. These allow you to access Web Services that are implemented as web sites, .NET, or other Caché systems. To implement a SOAP Client, the %SOAP.WebClient must be added to the Caché class. As with Web Services, the Web Client class must define the LOCATION, SERVICENAME and NAMESPACE parameters that match the service. The methods must be class methods and include the keyword WebMethod in their definition. The method signatures of the Web Client and the Web Service must match.

Bill's presentation slides are available in PowerPoint format. Also, the Caché 5 documentation includes excellent information on XML, SOAP and Web Services. NEMUG would like to thank Bill McCormick for his excellent and informative presentation.

~ submitted by Ben Hurley

back to the top