This document cannot be distributed without written permission from Geoffrey Fox (315-443-2163, gcf@npac.syr.edu).

1. Introduction *

2. Servlet architecture *

3. TDL - Template Definition Language *

4. Application Programming Interface for the servlet *

5. Servlet installation procedure *

6. Sample template - WebWisdom NT „CPS" template *

1. Introduction

1. Servlet architecture

The servlet is developed according to the requirements specified in [http://java.sun.com/products/ webserver/features/]. Thus, it can be used with any HTTP server fulfilling these requirements, for example Netscape Enterprise Server.

The servlet is composed of several modules (Fig. 2): Main Module with Initialization Module, Template Loader with Template Cache, XML Parser, Interpreter with Persistent Data Storage and Tag Implementations, and Sender with Output Cache.



Fig.2. Servlet architecture

First time the servlet is invoked, the Initialization module is activated. This module is responsible for reading configuration files, initializing all the data structures used by other modules, and initializing both cache modules.

The servlet can be remotely configured by the use of its HTTP server and a standard HTML browser. The configuration parameters include (among others) cache timings and methods, and names of Java methods to be used for tag interpretation. The Main Module is responsible for invoking and synchronizing the other modules. The order of invoking is the following. After a call is received from the HTTP server the servlet is linked to, servlet checks if the output for this call does not exists in the Output Cache (i.e., if the output for such call was already prepared and has not yet expired). If the output is ready in the Output Cache, it is sent directly to the user without activating other modules. If, however, the output for the call is not cached at the moment (or the cache is not active), the Main Module starts to activate other modules to perform this call. First, the Template Loader Module is activated with the template as a parameter. If this template file is stored in the Template Cache, it is passed to the Main Module. If, however, the template file is not cached at the moment, the Template Loader reads it from a given HTTP server, according to template locator. Once read, the template is put to the Template Cache and passed to the Main Module.

When the template is ready, the Main Module invokes the XML Parser for this template. As a result, a template derivation tree is generated, being a result of syntactical decomposition of the template. Each tag is stored as a node of the tree, with children nodes being nested tags, text inside tag body, and tag attributes. The root node of the generated parsing tree is passed back to the Main Module.

Once the tree for the template is ready, the Interpreter is invoked to parse the tree recursively, node by node. For every node, the tag type is determined and a corresponding Java method is invoked to generate tag output (i.e., a text in HTML format). The called method recursively calls similar methods for the nested elements of the tag body. Methods can access database management system (via JDBC) to get some data, read documents from HTTP servers, generate their own text, etc. As a final result of parsing the root node and all its children, a string of characters being HTML-formatted output is generated.

The Interpreter is also equipped in the Persistent Data Storage module, to deal with persistent objects (for example template variables) and to remember an interpretation state for some tags.

The generated HTML output is passed to the Sender, and, at the same time, to the Output Cache. The Sender sends via Internet (i.e., the HTTP server the servlet is linked to) the output back to the user.

In the remaining part of this section Modules are described in details.

1. Initialization Module

1. Main Module

1. Template Loader

TESS template is a set of files, stored in a single directory, written in TDL format, and defining a way of formatting output send to a client by the servlet. The TDL format is described in details in the next chapter. Each template has a name associated with it by the configuration file servlet_templ.conf (cf. Section 2.1). Each file belonging to a template is identified (in other files of the template) by its name. Some arguments may be passed from one template file to another during template interpretation.

Two files are treated in a special way. If the user accesses the template without specifying any particular file (for example http://taurus.kti.ae.poznan.pl/cps/), the default "login.tdl" template file is loaded. This file does not differ from other template files. However, if it contains special tag <WW_LOGINFORM>, the "SUBMIT" button will redirect control to the second special file – "index.tdl". Each template that requires user identification should use "login.tdl ® index.tdl" mechanism.

During the first attempt to use a template, a file called properties.conf is read (located in the template directory) to define some properties for the template. Properties are internal template variables. They are identified by names and they may have text values. The format of the properties.conf file conforms to XML and is a definition of a single XML tag <PROPERTIES>. Sample file is shown in Fig. 5. In this file there are two property definitions: property internal_name of value „P0ABC", and property display of value „My_comp". Both property names and values are case-insensitive. Properties are visible in all template files. However, they are local for its template and cannot be accessed by another template.

"<PROPERTIES>"

internal_name="P0ABC"

display="My_comp"

"</PROPERTIES>"

Fig.5. A sample contents of property definition file properties.conf

Some properties are predefined by the servlet and their role is set while the template is loaded. These properties are presented in the table below.

Property name	Meaning	Sample value
TEMPLATE_LOCATION	URL address of the directory with template files	http://www.npac.syr.edu
CONNECTION_STRING	Database connection string	Jdbc:oracle:thin:9001
SERVER_PORT	HTTP port number of a server the template is located	80
HOST_NAME	Name of the host on which the servlet is running	taurus.kti.ae.poznan.pl
SERVLET_DIR	Server directory where servlets are stored (usually server_root/Java/plugins/servlets)	Server_root/plugins/srv
TEMPLATE_ID	internal servlet template identifier	cps
USID	internal database user identifier of a user who invoked the template	-

Note that properties defined in templates (by the use of WW_SET tag described in the next chapter) are accessible in the same way as predefined properties mentioned above.

Each template file has the following structure:

<?TDLTEMPLATE?>

<?XML version="1.0"?>

<WW_DOCUMENT>

...

</WW_DOCUMENT>

with some tags inside a body of the <WW_DOCUMENT> tag. The body is written in TDL language described in Chapter 3. The tag definitions and their corresponding Java methods are user-defined (cf. Section 2.1). The complete example of a template is given in Chapter 5.

2. Template Cache

Once a template file is read from its HTTP server to the servlet, it is stored in a cache memory called the Template Cache. Each template has its own Template Cache with parameters set independently of each other. Next time the template file is addressed, the local, cached copy is taken rather than the original, remote one. The template files are cached once and stored in the Template Cache as long as their cache is not expired.. Thus, if a servlet is running and a given template file is changed, the cache should be expired to read the new version of this file (cf. Section 2.9).

3. XML Parser

1. Interpreter

The interpreter is responsible for parsing the derivation tree generated by the XML parser. As a parsing starting point the root node (corresponding to WW_DOCUMENT tag) is passed. Starting from this node, the tree is recursively parsed. For every node, a new instance of its interpreting Java class is loaded, and one selected method of this class is invoked (cf. Section 2.1 – configuration files). For tags declared as persistent, if this tag was already detected in the current template file, its previously created instance is used rather than a newly created one. Note that for multiple persistent tags related to one Java class (but possibly different methods of this class), their methods can communicate by the use of internal class variables.

Each interpreting method can use built-in servlet method parseChildren(). This method is responsible for recursive parsing of all nodes of the tree corresponding to tags nested in the current tag. If used, this method must be explicitly called from the tag interpreting method.

Each interpreting method may also use another built-in servlet method evaluateExpression(). This method is called with a text as its single argument. The method parses this text and changes all the valid expressions to their current values. Parts of text not being valid expressions are not changed. Detailed expression grammar is presented in the next chapter. The evaluateExpression() method is usually used to find current values of arguments passed to the interpreting method and current values of variables (properties).

Usually, one interpreting method is build over the following schema:

String interpretingMethod (String arg1, ..., String argN)

{

String result="";

arg1=evaluateExpression(arg1);

...

arg1=evaluateExpression(argN);

...Java code being tag interpretation and changing the result variable...

result+=parseChildren();

...Java code being tag interpretation and changing the result variable...

return result;

}

2. Sender

The sender is responsible for sending output - a string of characters being a result of parsing by the Interpreter the tree generated by the XML parser. The output is send back to the HTTP server to be sent to a client.

3. Output Cache

The output sent by the Sender to the HTTP server is at the same time stored in the Output Cache. If there is a next call to the same template with the same parameters, such cached output is sent back to avoid performing the whole output building cycle described in the previous sections. This approach may significantly improve the servlet performance, especially in the case when multiple users try to access the same data simultaneously (for example students participating in a class). The Output Cache is cleaned after a declared period of time, usually a few seconds. Cache expiration can be also caused by a specified number of hits. It allows more precise tuning of cache utilization. For example, if previously mentioned class of students consists of 12 people, cache expiration could be set to 13 hits (12+teacher). Thus, if data in the database are updated, the template reading this data will be updated too every time the whole class read a part of the course material, even if output for this data has been cached.

4. Remote Configuration

1. TDL - Template Definition Language

TDL (Template Definition Language) is an application of XML (Extensible Markup Language) for defining templates. The templates are used by the servlet to format data read from the database. TDL is not computing-complete and has similar power to UNIX shells. The language is based on XML definition on one hand, and typical UNIX shell commands and syntax on the other hand.

A template text is a sequence of XML tags with parameters. A tag is a command read and performed by a parser. As a parse output for a given tag (a set of tags) a part of HTML document is generated. Tags have names and they may have parameters, according to XML syntax. A parameter has a name and a text value. The values may be computed from expressions with syntax based on reverse Polish Notation (described further in details). Examples of tags are: <LOGIN>, <TEXT COLOR="black" SIZE="3">, etc.

Tags are always included inside ‘<’ and ‘>’ brackets. There is no possibility to nest tags, i.e. every ‘<’ character must be accompanied by ‘>’ character before a new ‘<’ is read beginning a new tag. Nevertheless, the language elements may be nested.

There are three types of tags. An empty tag is a stand-alone command that creates no context while it is parsed. Such tag is pointed out by "/" character before the closing ‘>’ bracket. Examples of empty tags are: <DATE/>, <AUTHOR/>, etc.

A pair of start and end tags defines an element. Everything between a start tag and its counterpart is named element’s body and is being interpreted according to the tag type. Start-end pairs of tags may be arbitrarily nested, on condition they are closed by ‘>’ characters. An empty tag may be also nested in a start-end pair of tags. An end tag has the same name as the corresponding start tag, except it has ‘/’ character as its name prefix. Examples of start-end tags are: <AUTHOR> </AUTHOR>, <BOLD> </BOLD>, <TEXTEFFECTS BOLD="on" ITALICS="off"> </TEXTEFFECTS>, etc. Both start and end tags may have parameters, although the parameters are mainly used for start tags.

Tag names and syntax are completely user defined, by the use of the configuration files read by the server before its first execution. This file contains entries composed of tag name, corresponding Java class/method and parameters. In this file, a tag and an appropriate Java class/method to generate HTML output is stored. The methods may query the database. Detailed syntax of a servlet configuration file is described in Section 2.1.

There are also some predefined control tags which do not generate explicit HTML output but are used to control the process of parsing a template. Control tags also can be changed by a user and they are listed in the configuration file. They are based on typical UNIX shell syntax (very limited, however) with extensions specific for XML. Control tags are either empty or start-end tags. Below a list of control tags is presented.

1. Expressions

In most places in TDL instead of simple values, expressions can be used (e.g., to define current values of parameters of some TDL tags). An expression is a string inside apostrophes (") of valid syntax. Expressions are always string-oriented, i.e. arguments as well as an output are strings of characters. Some strings may contain numeric values, evaluated by Java classes/methods to another strings with numeric values. This approach simplifies the process of defining and using templates as well as the servlet internal structure.

To define an order of operations inside an expression, extended Reverse Polish Notation is used.

As expressions being parameters of XML tags are processed outside XML parser, their syntax (described below in details) cannot be changed by a user. There is a possibility, however, to extend expressions by direct calling to Java methods performing specific operations on their parameters. For example, it is possible to implement arithmetic operations, advanced operations on strings, specialized database queries, etc.

Boolean values are defined by special strings: false by the empty string, and true by any non-empty string, in particular "true". This implementation detail, however, should not be explicitly addressed by templates, i.e. one should avoid using syntax like <WW_IF CONDITION="">.

Expressions are given in ‘"’ characters according to XML rules. Expressions are evaluated from left to right, and every evaluated part is concatenated at the end of the output string. Non-string elements (functions, constants, and variables) are always prefixed by special characters. This approach is similar to the one used in UNIX shell scripts and "printf" function in C/C++ programming language.

The simplified syntax for expressions is given below in BNF-like notation.

Expression ::= Variable |

Constant |

%equ[al](ExpressionList) |

%dif[ferent] (ExpressionList) |

%or (ExpressionList) |

%and (ExpressionList) |

%gre[ater] (ExpressionList) |

%les[s] (ExpressionList) |

%nog[reater] (ExpressionList) |

%nol[ess] (ExpressionList) |

%tol[ower] (ExpressionList) |

%tou[pper] (ExpressionList) |

%tri[m] (ExpressionList) |

%nos[pace] (ExpressionList) |

%add(ExpressionList) |

%mul[tiply](ExpressionList) |

%div[ide](ExpressionList) |

%sub[stract](ExpressionList) |

%sum(ExpressionList) |

%min[imum](ExpressionList) |

%max[imum](ExpressionList) |

%not (Expression)

ExpressionList ::= Expression , ExpressionList |

Expression

 

Variable ::= ${variable_name} | // access to a value of a variable

`class.method(par)` //direct Java invocation,

//the string must not contain ‘`’ character

$$ | ${$} | // ‘$’ character itself

$` | ${`} | // ‘`’ character itself

$% | ${%} | // ‘%’ character itself

$, | ${,} | // ‘,’ character itself

$} | // ‘}’ character itself

${quot} | // ’"’ character itself

${true} | // boolean value "true"

${false} | // boolean value false, equivalent to an empty string

$$

Constant ::= string | // string with no delimiters (may have ‘}’ characters inside)

%{string} // any string of characters with no ‘}’ character inside

Functions prefixed by ‘%’ character can have any number of parameters (separated by ‘,’ characters) starting from one parameter. All the parameters are evaluated from left to right. For example, a call "%equal(ANNA, DOROTHY, EVE)" gives false as a result, while "%equal(2,2,2,2,2)" - true. Of course, they may be invoked with exactly two parameters as in classical programming languages.

Variable_name is a string-based name of a variable. The name must not contain "}" character. A value of a variable is also string-based. If a variable was not set before first access for its value, this value is automatically set to an empty string at the moment of the access. There is a possibility to perform arithmetic operation on variables – in such case Java methods treat strings as encoded numbers of type "integer" or "real".

${variable_name} stands for an access to a value of a given variable.

Sub-parts of expressions inside a pair of ‘`’ characters are treated as calls to Java methods. In such a case, first all the prefixes inside the sub-expressions are detected and evaluated (recursively), eventually updating a string being a Java call. Next, the resulted string is evaluated as a call to Java method of a given class with given parameters. For example, a sub-expression:

`math.add(${foil_number},1)`

is first evaluated to (assuming a value of the variable "foil_number" is currently equal to "44")

`math.add(44,"1")`

and finally after performing a Java call to string "45", while sub-expression:

`string.add(${quot}${foil_name}${quot},${quot} number${quot})`

is first evaluated to (assuming a value of the variable "foil_name" is currently equal to "Appendix")

`string.add("Appendix"," number")`

and finally after performing a Java call to string "Appendix number".

Some variables are predefined by the servlet (as properties, cf. Section 2.1).

Prefix ‘%’ for a string-based constant is added for simplicity, to facilitate entering strings containing special characters used usually as prefixes for functions and variables. For example, one can use any of the below expressions to enter string "100% and $100,00":

"100${%} and ${$}100,00"

or simply:

"%{100% and $100,00}"

Examples of expressions are:

"some ${var1} have ${var2}" // for var1=animals , var2=eyes, output is "some animals have eyes"

"Author: `databaseDirectCall.getAuthorName()`" // sample output is "Author: Smith"

2. Conditional statements

TDL allows for conditional inclusion of fragments of templates. Conditional statements are expressed by the WW_IF element. It is a non-empty XML element whose body is included in the outcome only when the specified condition is satisfied. This element has an optional part(s) included when the specified condition is not satisfied.

The syntax of the IF statement is the following:

<WW_IF CONDITION="...">

<WW_THEN>

</WW_THEN>

<WW_ELSE>

</WW_ELSE>

</WW_IF>

Inside the WW_IF element an optional WW_ELSE element can be included. If the condition evaluates to true, the code included in the WW_THEN element is interpreted. Otherwise the part of code included in the WW_ELSE element is interpreted. There could be multiple WW_ELSE and WW_THEN parts. These parts must be included between WW_IF and /WW_IF tags. The case when it is only one WW_THEN part, followed by WW_ELSE part, followed immediately by /WW_IF tag is similar to typical IF-THEN-ELSE control statement from many programming languages.

The WW_IF tag has only one attribute: CONDITION. This attribute contains an expression string that is evaluated to a boolean value.

3. Assigning values to internal servlet variables

1. Inserting values

Values of internal servlet variables and dynamically computed expressions can be included into the output by the use of WW_INSERT command. This command is implemented by empty WW_INSERT tag. Note that, in comparison to WW_SET tag, this tag generates directly an output rather than storing a new value of a given variable.

The syntax of the WW_INSERT element is the following:

<WW_INSERT VALUE="..."/>

The parser replaces the WW_INSERT tag with the value calculated from the contents of the VALUE attribute being an expression.

2. Connecting to database

1. Invoking another template file

The control may be passed from one template file to another by the use of <WW_LINK> element. In the attributes of this element one can specify a filename of a template file the control is passed to, and some parameters. The parameters are separated by ‘|’ character. Each parameter definition is composed of a parameter name (i.e., a property for a calling template file) and an expression reflecting current property value, separated by ‘=’ character. For example, the text ATTR="PID=1 | FID=${FID}" is a definition of two parameters, the first one with name PID and constant value 1, and the second one with name FID and a value equal to current value of variable FID.

The syntax of the WW_LINK element is the following:

<WW_LINK FILENAME="..." ATTR="..."/>

2. Inline command

1. Application Programming Interface for the servlet

The servlet is equipped with a set of methods to be used in user-defined interpretation methods for tags. These methods are provided as parts of system-defined abstract class TDLTag. To define an interpretation method for a tag one should first create a new class (of any name) being an extension of the TDLTag class and next provide in it a method to interpret the tag:

public class Tags extends TDLTag {

//private variables

interpretation_method(String param1, …, String paramN) {

…

}

// private functions

}

The interpretation_method may use any of the build-in API functions described in Section 4.1. Sample interpretation functions for control tags are described in Section 4.2.

The classes and methods for tag interpretation must be declared in the configuration file servlet_tdl.conf (cf. Section 2.1).

1. API functions from TDLTag abstract class

public abstract class TDLTag {

public TDLTag() {}

// empty contructor

public InputStream getFileHandle (String fileName);

// returning a handle to current template file

public void removeAttrValue (String name);

// removing a property from property table

public String getStringAttrValue(String name);

// getting a value of a property and returning it as a string

public int getIntAttrValue(String name);

// getting a value of a property and returning it as an integer value

// if a conversion from string to integer cannot be done, returning value 0

public float getFloatAttrValue(String name);

// getting a value of a property and returning it as a float value

// if a conversion from string to integer cannot be done,

// returning value 0.0

public boolean setStringAttrValue(String name, String value);

// setting a string value of a property

// returning true if everything is OK, false if a property cannot be set

public boolean setFloatAttrValue(String name, float value) {

// setting a float value of a property

// returning true if everything is OK, false if a property cannot be set

public boolean setIntAttrValue(String name, int value) {

// setting an integer value of a property

// returning true if everything is OK, false if a property cannot be set

final String parseChildren();

// parsing body of the tag

public String evaluateExpression (String expression);

// parsing string from left to right

// and evaluating all the valid expressions to their current values

// parts of string not being valid expressions remain unchanged

}

2. Example implementation of methods for control tags

import java.io.*;

import java.util.*;

import java.sql.*;

import java.sql.Date;

import db.*;

import view.*;

public class Tags extends TDLTag {

...

/**

* Main tag for all TDL documents. Standard TDL tag implementation.

* @return Parsed contents

*/

public String WW_DOCUMENT () {

return parseChildren();

// parse all children

}

 

/**

* IF statement. Standard TDL tag implementation.

* <b>Must be used with THEN and/or ELSE tags</b>.

* @param condition - <code>if</code> condition

* @return Parsed contents

*/

public String WW_IF (String condition) {

String res="";

condition = evaluateExpression(condition);

setIntAttrValue(Constants.IFLevelProperty,

getIntAttrValue(Constants.IFLevelProperty)+1);

// setting a temporary property with current value of the condition

if (condition!="")

setIntAttrValue(Constants.IFLevelConditionProperty+

getIntAttrValue(Constants.IFLevelProperty),1);

else

setIntAttrValue(Constants.IFLevelConditionProperty+

getIntAttrValue(Constants.IFLevelProperty),0);

res+=parseChildren();

// removing temporary property

removeAttrValue(Constants.IFLevelConditionProperty+

getIntAttrValue(Constants.IFLevelProperty));

setIntAttrValue(Constants.IFLevelProperty,

getIntAttrValue(Constants.IFLevelProperty)-1);

return res;

}

/**

* THEN statement. Standard TDL tag implementation.

* Have to be used only in IF tag context.

* @return Parsed contents

*/

public String WW_THEN () {

if (getIntAttrValue(Constants.IFLevelConditionProperty+

getIntAttrValue(Constants.IFLevelProperty))==1)

return parseChildren();

else

return "";

}

/**

* ELSE statement. Standard TDL tag implementation.

* Have to be used only in IF tag context.

* @return Parsed contents

*/

public String WW_ELSE () {

if (getIntAttrValue(Constants.IFLevelConditionProperty+

getIntAttrValue(Constants.IFLevelProperty))==0)

return parseChildren();

else

return "";

}

/**

* Inserts result of the calculation or the variable value.

* Standard TDL tag implementation.

* @param name - variable or expression

* @return String with a value

*/

public String WW_INSERT(String name) {

return evaluateExpression(name);

}

/**

* Inserting result of the calculation or the variable value

* into <code>name</code> variable. Standard TDL tag implementation.

* @param name - name of the variable

* @param value - variable or expression value

* @return Empty string

*/

public String WW_SET (String name, String value) {

name = evaluateExpression(name);

value = evaluateExpression(value);

setStringAttrValue(name,value);

return "";

}

 

 

/**

* Connecting to database. Standard TDL tag implementation.

* @param connection - connection string, if <code>connection</code> is empty,

* default value is taken from property file.

* @return Empty string

*/

public String WW_CONNECT (String connection) {

connection = evaluateExpression(connection);

if (connection.equals(""))

connection=getStringAttrValue(Constants.ConnectionStringProperty);

else

setStringAttrValue(Constants.ConnectionStringProperty,connection);

try {

setConn (DriverManager.getConnection(connection));

} catch (SQLException e) {

ExceptionHandler.handleException(e,"TAGS:WW_CONNECT");

}

return "";

}

...

}

/**

* Process its contents inserting into the <code>name</code> variable

* id’s of foilworlds that are in the foilworld specified by <code>fwid<code>

*

* @param fwID - foilworld id

* @param name - name of the variable

*

* @return Parsed contents

*

* @version 1.0 07/15/98

*/

public String WW_FOILWORLDLOOP (String fwID, String name) {

name = evaluateExpression(name);

fwID = evaluateExpression(fwID);

String res = "";

String query = "SELECT WID FROM FOILWORLD WHERE BUFFER_OWNER_UID IS

NULL AND WID<>1 AND BELONGS_TO_WID = "+fwID+" ORDER BY NAME";

try {

Statement sqlStatement =

tdlTemplate.getCon().createStatement();

ResultSet rs = sqlStatement.executeQuery(query);

while (rs.next()) {

setStringAttrValue(name,rs.getString("WID"));

res+=parseChildren();

}

rs.close(); sqlStatement.close();

} catch (SQLException e) {

ExceptionHandler.handleException(e,"TAGS:WW_FOILWORLDLOOP");

}

return res;

}

 

/**

* Process the contents inserting into the <code>name</code> variable

* id's of presentations from the foilworld specified by <code>fwid<code>

*

* @param fwID - foilworld id

* @param name - name of the variable

*

* @return Parsed contents

*

* @version 1.0 07/15/98

*/

public String WW_PRESENTATIONLOOP (String fwID, String name) {

name = evaluateExpression(name);

fwID = evaluateExpression(fwID);

String res = "";

String query = "SELECT COMPONENT_PID FROM FW_CONTAIN_PR WHERE

CONTAINER_WID="+fwID;

try {

Statement sqlStatement =

tdlTemplate.getCon().createStatement();

ResultSet rs = sqlStatement.executeQuery(query);

while (rs.next()) {

setStringAttrValue(name,rs.getString("COMPONENT_PID"));

res+=parseChildren();

}

rs.close(); sqlStatement.close();

} catch (SQLException e) {

ExceptionHandler.handleException(e,"TAGS:WW_PRESENTATIONLOOP");

}

return res;

}

/**

* Process the contents inserting into the <code>name</code> variable foil

* id's from the presentation specified by <code>parentID<code>

*

* @param parentID - presentation id

* @param name - name of the variable

*

* @return Parsed contents

*

* @version 1.0 07/15/98

*/

public String WW_FOILLOOP (String parentID, String name) {

name = evaluateExpression(name);

parentID = evaluateExpression(parentID);

String res="";

Vector vc = new Vector();

fillFoilID(parentID, vc);

Enumeration en = vc.elements();

while (en.hasMoreElements()) {

setStringAttrValue(name,(String)en.nextElement());

res+=parseChildren();

}

return res;

}

2. Servlet installation procedure

1. Sample template - WebWisdom NT „CPS" template

This template is used in the WebWisdom NT 2.1 system do give access to foils and other teaching material. This is a template originally prepared for WebWisdom 1.0 system and it was adapted with some changes.

1. Tag definition

There is a set of tags defined in the servlet configuration file to be used with the „CPS" template. The tag names begin with „WW_" prefix. In the table below all tags used by the „CPS" template are presented in details. All the tags except WW_COUNTER are declared as non-persistent (cf. Section 2.1).

Tag name	Java class/method invoked	Purpose
WW_ABSMISSING	Tags.WW_ABSMISSING ( PRESENTATIONID)	inserting HTML "HREF" link to the template file that is capable to access an image version of an abstract of presentation PARENTID
WW_ABSTRACTIMAGE	Tags.WW_ABSTRACTIMAGE ( PRESENTATIONID)	inserting an image of an abstract of presentation PRESENTATIONID
WW_ABSTRACTTEXT	Tags.WW_ABSTRACTTEXT ( PRESENTATIONID)	inserting a text (HTML bulleted list) of an abstract of presentation PRESENTATIONID
WW_ADDON	Tags.WW_ADDON ( FOILID, PARENTID)	inserting add-on for foil FOILID in presentation PARENTID
WW_ANNOTATION	Tags.WW_ANNOTATION ( PRESENTATIONID, POSITION)	inserting an annotation belonging to presentation PRESENTATIONID at position POSITION
WW_AUTHORNAME	Tags.WW_AUTHORNAME ( FOILID, PARENTID)	inserting name of primary author of foil FOILID in presentation PARENTID
WW_BODYIMAGE	Tags.WW_BODYIMAGE (FOILID, PARENTID)	inserting 'body' HTML tag with background image typical for foil files for foil FOILID in presentation PARENTID
WW_BODYINDEX	Tags.WW_BODYINDEX ( PRESENTATIONID)	inserting 'body' HTML tag with background image typical for index files for presentation PRESENTATIONID
WW_BODYSEPHTML	Tags.WW_BODYSEPHTML ( FOILID, PRESENTATIONID)	inserting HTML "BODY" tag for templates for displaying text-based HTML version of foil FOILID in presentation PRESENTATIONID rather than its image version
WW_CONNECT	Tags.WW_CONNECT ( CONNECTION)	connecting to the database with connection string CONNECTION
WW_COUNTER	Pers.WW_COUNTER( )	the only persistent tag counting references to the template
WW_CREATIONDATE	Tags.WW_CREATIONDATE ( FOILID)	inserting date of creation of foil FOILID
WW_DBSET	Tags.WW_DBSET ( NAME, PROPNAME, PROPTYPE, FOILID, PARENTID)	taking signature value from database property in context of current user, presentation, and foil; PROPTYPE attribute specifies the type of the property, ('overall' in case of the signature), PROPNAME specifies the database property name; the value of the property is assigned to a variable with name given by NAME attribute
WW_DEFAULTBG	Tags.WW_DEFAULTBG ( )	taking default background image for foils
WW_DEFAULTLOGO	Tags.WW_DEFAULTLOGO ( )	taking defaults logo image
WW_DOCUMENT	Tags.WW_DOCUMENT ( )	root XML/TDL „document" tag, a container for all other tags (like an 'html' tag in HTML)
WW_ELSE	Tags.WW_ELSE ( )	ELSE control statement
WW_EVENT	Tags.WW_EVENT ( FOILID )	inserting primary event related to a foil FOILID
WW_EVENTDATE	Tags.WW_EVENTDATE ( FOILID)	inserting primary event date of an event associated with FOILID
WW_EXTERNALURL	Tags.WW_EXTERNALURL ( FOILID, PARENTID )	inserting HREF tag pointed to external location for foil FOILID in presentation PARENTID
WW_FIRSTFOIL	Tags.WW_FIRSTFOIL ( PARENTID, NAME )	inserting into NAME variable identifier of the first foil of presentation PARENTID
WW_FOIL	Tags.WW_FOIL ( FOILID, PARENTID, MODE )	inserting an image or text-based version of foil FOILID in presentation PARENTID based on MODE value (IMAGE,TEXT or ASNEEDED)
WW_FOILIMAGE	Tags.WW_FOILIMAGE ( FOILID, PARENTID )	inserting an image of foil FOILID in presentation PARENTID
WW_FOILLINK	Tags.WW_FOILLINK ( FOILID, FILENAME, ATTR )	inserting a HREF link to template file FILENAME with foil FOILID and parameters ATTR; it allows to create an 'index' of all foils contained in a given presentation
WW_FOILLOOP	Tags.WW_FOILLOOP ( PARENTID, NAME )	tag iterates for all foils in PARENTID presentation each time assigning current child foil ID to NAME variable
WW_FOILNUMBER	Tags.WW_FOILNUMBER ( PARENTID, FOILID )	inserting foil number for foil FOILID in presentation PARENTID
WW_FOILTEXT	Tags.WW_FOILTEXT ( FOILID )	inserting HTML bulleted list of foil FOILID
WW_FOILWORLDLINK	Tags.WW_FOILWORLDLINK ( FWID, FILENAME, ATTR)	inserting a HREF link to template file FILENAME with foilworld FWID and parameters ATTR; it allows to create an 'index' of all foilworlds contained in a given foilworld
WW_FOILWORLDLOOP	Tags.WW_FOILWORLDLOOP ( FWID, NAME )	parsing in a loop contents of foilworld FWID, setting for each loop pass a variable given by NAME attribute. This variable contains an identifier of a 'child' foilworld. The loop is repeated as many times as many child foilworlds the given foilworld contains.
WW_FWPARENTLINK	Tags.WW_FWPARENTLINK ( FWID, FILENAME, ATTR)	inserting HREF tag with a pointer to foilworld containing current presentation by the use of template file FILENAME with attributes ATTR
WW_IF	Tags.WW_IF ( CONDITION )	IF control statement
WW_IMAGE	Tags.WW_IMAGE ( IMAGENAME, FOILID, PARENTID )	inserting an image of name IMAGENAME associated with foil FOILID in presentation PARENTID
WW_INSERT	Tags.WW_INSERT ( NAME )	inserting current value of an expression to evaluate; an expression could be a variable evaluation
WW_LINK	Tags.WW_LINK ( FILENAME, ATTR)	inserting contents generate by the use of another template file FILENAME invoked with parameters ATTR
WW_LOGIN	Tags.WW_LOGIN ( )	log-in page to the WebWisdom NT system
WW_LOGINFORM	Tags.WW_LOGINFORM( ) Built-in servlet method	user identification form - after detecting this tag the "SUBMIT" button of this form will redirect control to the special template file – "index.tdl" (cf. Section 2.3)
WW_MISSING	Tags.WW_MISSING ( FOILID, PARENTID )	inserting HTML "HREF" link to the template file that is capable to access an image version of foil FOILID in presentation PARENTID
WW_MODIFICATIONDATE	Tags.WW_MODIFICATIONDATE ( FOILID )	inserting date of last modification of foil FOILID
WW_NEXT	Tags.WW_NEXT ( PARENTID, FOILID, FILENAME, IMAGENAME )	inserting a button with HREF links to template file FILENAME with next foil in the presentation PARENTID after foil FOILID; IMAGENAME is a name of the property defining image
WW_NOBULLETSIFGIF	Tags.WW_NOBULLETSIFGIF ( FOILID)	inserting HTML bulleted text if there is no corresponding image for foil FOILID
WW_NOTE	Tags.WW_NOTE( FOILID, PARENTID)	Inserting a HTML bulleted list of a note of foil FOILID in presentation PARENTID
WW_NUMBEROFFOILS	Tags.WW_NUMBEROFFOILS ( PARENTID )	inserting number of foils in presentation PARENTID
WW_OWNERNAME	Tags.WW_OWNERNAME ( FOILID)	inserting name of owner of foil FOILID
WW_PASSWORD	Tags.WW_PASSWORD( ) Build-in servlet method	user identification tag – a text field in the log-in form to enter user’s password
WW_PRESENTATIONLINK	Tags.WW_PRESENTATIONLINK ( PRESENTATIONID, FILENAME, ATTR)	inserting a HREF link to template file FILENAME with presentation PRESENTATIONID and parameters ATTR; it allows to create an 'index' of all presentations contained in a given foilworld
WW_PRESENTATIONLOOP	Tags.WW_PRESENTATIONLOOP ( FWID, NAME)	parsing in a loop contents of foilworld PARENTID, setting for each loop pass a variable given by NAME attribute. This variable contains an identifier of a child presentation. The loop is repeated as many times as many presentations the given foilworld contains.
WW_PREV	Tags.WW_PREV ( PARENTID, FOILID, FILENAME, IMAGENAME)	inserting a button with HREF links to template file FILENAME with previous foil in the presentation PARENTID before foil FOILID; IMAGENAME is a name of the property defining image
WW_RUNNINGTITLE	Tags.WW_RUNNINGTITLE ( FOILID)	inserting foil „running title" of foil FOILID
WW_SELECTADDON	Tags.WW_SELECTADDON ( FOILID, NAME)	checking for the existence of add-on in foil FOILID; if an add-on is associated with the specified foil, the ID of the database object containing add-on is inserted into variable given by the NAME attribute.
WW_SELECTCOMMENT	Tags.WW_SELECTCOMMENT ( FOILID)	inserting text-based comment for foil FOILID
WW_SELECTDISPMODE	Tags.WW_SELECTDISPMODE ( FOILID, NAME)	tag inserts into variable with name given by NAME attribute the preferred display mode of foil FOILID
WW_SELECTEXTERNAL	Tags.WW_SELECTEXTERNAL ( FOILID)	if there is an external link defined for foil FOILID, parsing body of the tag
WW_SELECTIMAGE	Tags.WW_SELECTIMAGE ( FOILID)	if there is an image defined for foil FOILID, parsing body of the tag
WW_SELECTNOTE	Tags.WW_SELECTNOTE ( FOILID)	if there is a note defined for foil FOILID, parsing body of the tag
WW_SELECTSOUND	Tags.WW_SELECTSOUND ( FOILID, NAME)	checking for the existence of sound in foil FOILID; if a sound is associated with the specified foil, the ID of the database object containing sound is inserted into variable given by the NAME attribute.
WW_SELECTSOURCEFOIL	Tags.WW_SELECTSOURCEFOIL ( FOILID)	if there is source PowerPoint file defined for foil FOILID, parsing body of the tag
WW_SELECTSOURCEMASTER	Tags.WW_SELECTSOURCEMASTER( FOILID)	if there is source PowerPoint "master" file for foil FOILID, parsing body of the tag
WW_SELECTSOURCEPRES	Tags.WW_SELECTSOURCEPRES ( FOILID)	if there is source PowerPoint file with presentation containing source for foil FOILID, parsing body of the tag
WW_SELECTTEXT	Tags.WW_SELECTTEXT ( FOILID)	if there is HTML-based text data defined for foil FOILID, parsing body of the tag
WW_SET	Tags.WW_SET ( NAME, VALUE)	setting a new value VALUE for a variable (property) NAME
WW_SETPOSITION	Tags.WW_SETPOSITION ( PARENTID, FOILID, NAME)	innserting foil position of foil FOILID in presentation PARENTID into variable NAME
WW_SOUND	Tags.WW_SOUND (FOILID, PARENTID)	inserting sound data for foil FOILID in presentation PARENTID
WW_THEN	Tags.WW_THEN ( )	THEN control statement
WW_TITLE	Tags.WW_TITLE ( FOILID)	inserting foil title of foil FOILID
WW_TITLEFOILWORLD	Tags.WW_TITLEFOILWORLD ( FWID)	inserting a title of foilworld FWID
WW_USERNAME	Tags.WW_USERNAME( Built-in servlet method	user identification tag – a text field in the log-in form to enter user’s name

In the succeeding sections of this chapter the „CPS" template files are presented with some comments inside describing a purpose of using some tags. The TDL tags are printed in bold.

2. Main template file

<?WWTEMPLATE>

<?XML VERSION="1.0" CACHE="NO"?>

<WW_DOCUMENT>

<!-- This is a first file of the template.

If in the URL, after the name of the template, the filename is omitted,

the index.tdl file is read by default.

-->

<!-- ?WWTEMPLATE and ?XML tags form a header for all template files.

CACHE attribute of the XML tag specifies whether the servlet should cache

this file or not.

-->

<!-- The main task of this file is to redirect a user to a list of foilworlds.

This is implemented by a JavaScript function that redirects to

the following URL:

tempfoilworld.tdl?FWID=1.

The tempfoilworld.tdl file lists all foilworlds and presentations

in a foilworld identified by FWID parameter (1 identifies the root foilworld)

-->

<html>

<head>

<title>Get WebWisdom NT Started</title>

</head>

<script LANGUAGE="JavaScript">

<!-- function a ()

{top.location.href = "tempfoilworld.tdl?FWID=1";}

-->

</script>

<body background="greymarb.gif" >

<h1>Click The Correct Button to Get to WebWisdom NT</h1>

<form>

<b>Click this if you have Netscape 3.0(but not 2.0 which is confused by Complex Javascript). <br> If you don't have a JavaScript Multiframe system,

other links below form will take you to where you want to go with lower technology!<br>

</b>

<form>

<input type="button" value="Start Click Here!" onClick="a()">

</form>

<br>WebWisdom NT is a JavaScript and servlet-based system for managing hierarchically arranged information such as you get in Education as you span lectures, courses, degrees, departments, Universities. The database available here illustrates 3 worlds:

<b>

<ul>

<li>Administration,

<li>The Virtual University with Courses(electronic foils) and the

<li>Virtual Family (photo sets)</b>

</ul>

<center><img align=top src="WEBWIS2.JPG" BORDER="5" HSPACE="5" VSPACE="5"></center>

<br>

<br>

<center><h2>The Tree of Wisdom </h2></center>

<center><img src="maplerun7.gif" ></center>

</body>

</html>

</WW_DOCUMENT>

3. Template file to display foils as HTML-bulleted lists

<?WWTEMPLATE>

<?XML VERSION="1.0" CACHE="NO"?>

<WW_DOCUMENT>

<WW_CONNECT CONNECTION=""/>

<!-- See comments in tempfoilsepimage.tdl for detailed info-->

<html>

<head>

<title> Separate HTML for LOCAL Foil

<WW_FOILNUMBER PARENTID="${PID}" FOILID="${FID}"/> <WW_TITLE FOILID="${FID}"/>

</title>

</head>

<WW_BODYSEPHTML/>

<b>

<WW_LINK FILENAME="temphelp.tdl" ATTR="">HELP!</WW_LINK>

GREY=local</b><tt> LOCAL HTML version of Foils prepared

<WW_MODIFICATIONDATE FOILID="${FID}"/> </tt>

<h2> Foil <WW_FOILNUMBER PARENTID="${PID}" FOILID="${FID}"/>

<WW_TITLE FOILID="${FID}"/> </h2>

<b> <i>From</i>

<WW_RUNNINGTITLE FOILID="${FID}"/>

<WW_EVENT FOILID="${FID}"/> --

<WW_EVENTDATE FOILID="${FID}"/>. <i>by</i>

<WW_AUTHORNAME FOILID="${FID}"/> </b> *

<WW_MISSING FOILID="${FID}" PARENTID="${PID}"/>

<hr>

<!-- WW_NEXT and WW_PREV insert buttons with HREF links to next and

previous foil in the current presentation. FOILID and PARENTID

attributes specify IDs of current foil and current presentation,

FILENAME is a template filename (usually the same as current)

and IMAGENAME is a name of the property defining image

that should be used for the button.

-->

<WW_NEXT FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsephtml.tdl" IMAGENAME="ww_next"/>

<WW_PREV FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsephtml.tdl" IMAGENAME="ww_prev"/>

<WW_LINK FILENAME="tempfullindex.tdl" ATTR="PID=${PID}">

<WW_IMAGE IMAGENAME="ww_up" FOILID="${FID}" PARENTID="${PID}"/>

</WW_LINK>

<!-- WW_SELECTSOUND checks for the existence of sound in the

foil. If a sound is associated with the specified foil, the ID of the

eduobject containing sound is inserted into variable given by the NAME

attribute.

The same is accomplished by WW_SELECTADDON tag for presentation/foil

add-ons

-->

<WW_SELECTSOUND FOILID="${FID}" NAME="ISSOUND">

<INSERT NAME="${ISSOUND}"/>

</WW_SELECTSOUND>

<WW_SELECTADDON FOILID="${FID}" NAME="ISADDON">

<INSERT NAME="${ISADDON}"/>

</WW_SELECTADDON>

<hr>

<WW_FOILTEXT FOILID="${FID}"/>

<hr>

<WW_NEXT FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsephtml.tdl" IMAGENAME="ww_next"/>

<WW_PREV FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsephtml.tdl" IMAGENAME="ww_prev"/>

<WW_LINK FILENAME="tempfullindex.tdl" ATTR="PID=${PID}">

<WW_IMAGE IMAGENAME="ww_up" FOILID="${FID}" PARENTID="${PID}"/>

</WW_LINK>

<!-- The following pair of tags inserts into output text the signature

for current foil/presentation.

First the WW_DBSET tag takes signature value from database property

in context of current user, presentation, and foil.

PROPTYPE attribute specifies the type of the property

('overall' in case of the signature),

PROPNAME specifies the database property name.

The value of the property is assigned to a variable with name given

by NAME attribute - here: SIG.

WW_INSERT inserts the value of the signature (here variable value)

into output text.

-->

<WW_DBSET NAME="SIG" PROPNAME="signature" PROPTYPE="OVERALL" FOILID="${FID}" PARENTID="${PID}"/>

<WW_INSERT NAME="${SIG}"/>

</WW_DOCUMENT>

 

4. Template file to display foils as images

<?WWTEMPLATE>

<?XML VERSION="1.0" CACHE="NO"?>

<WW_DOCUMENT>

<!-- ?WWTEMPLATE and ?XML tags form a header for all template files.

CACHE attribute of the XML tag specifies whether the servlet should

cache the file or not.

-->

<!-- WW_CONNECT is a tag that establishes a connection to the database.

Connection string may be supplied in the CONNECTION attribute,

or if it is omitted (empty string) the default connection string is

taken from properties.txt file for current template.

-->

<WW_CONNECT CONNECTION=""/>

<html>

<head>

<title> Separate IMAGE for LOCAL foil

<!-- WW_FOILNUMBER tag takes the position of the current foil in the current

presentation.

BUG! Because of the presentation nesting it returns false results

for nested presentations and foils

-->

<WW_FOILNUMBER PARENTID="${PID}" FOILID="${FID}"/>

<!-- WW_TITLE is a tag that allows to insert title of a presentation or foil.

The presentation/foil is identified by an ID supplied in FOILID attribute.

PARENTID is not currently used by the WW_TITLE tag, but can be later

used, e.g. to check the formatting properties, which can be defined on

the presentation level.

FID and PID were supplied by the servlet from query attributes of the URL

-->

<WW_TITLE FOILID="${FID}"/> </title>

</head>

<!-- WW_BODYIMAGE inserts a 'body' HTML tag with background image typical

for foil files. This tag should be reimplemented to take images from DB

-->

<WW_BODYIMAGE/>

<tt><a href="#image">Image</a><a href="#buttons"> Buttons</a> </tt>

<b><WW_LINK FILENAME="temphelp.tdl" ATTR="">HELP!</WW_LINK>

* GREY=local</b><tt> LOCAL IMAGE version of Foils prepared

<!-- WW_MODIFICATIONDATE inserts modification date of the current foil -->

<WW_MODIFICATIONDATE FOILID="${FID}"/> </tt>

<h2> Foil <WW_FOILNUMBER PARENTID="${PID}" FOILID="${FID}"/>

<WW_TITLE FOILID="${FID}"/> </h2>

<b> <i> From </i>

<!-- WW_RUNNINGTITLE inserts running title of the specified foil. WW_EVENT,

WW_EVENTDATE, and WW_AUTHORNAME get appropriate data for the current foil

from the database

-->

<WW_RUNNINGTITLE FOILID="${FID}"/>

<WW_EVENT FOILID="${FID}"/> -- <WW_EVENTDATE FOILID="${FID}"/>. <i>by</i> <WW_AUTHORNAME FOILID="${FID}"/></b>

<!-- This WW_LINK tag inserts a link to the HTML version of the

current foil -->

<WW_LINK FILENAME="tempfoilsephtml.tdl" ATTR="FID=${FID}|PID=${PID}">* HTML Version</WW_LINK>

<hr>

<a name="buttons">

<!-- WW_NEXT and WW_PREV insert buttons with HREF links to next and

previous foil in the current presentation. FOILID and PARENTID attributes

are IDs of current foil and current presentation, FILENAME is a template

filename (usually the same as the current),

and IMAGENAME is a property name specifying the image that should be

used for link button.

-->

<WW_NEXT FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsepimage.tdl" IMAGENAME="ww_next"/>

<WW_PREV FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsepimage.tdl" IMAGENAME="ww_prev"/>

<WW_LINK FILENAME="tempfullindex.tdl" ATTR="PID=${PID}">

<WW_IMAGE IMAGENAME="ww_up" FOILID="${FID}" PARENTID="${PID}"/>

</WW_LINK>

<!-- WW_SELECTSOUND checks for the existence of the sound in the

foil. If a sound object is associated with the specified foil, the ID of

the eduobject containing sound is assigned to a variable given by

NAME attribute.

The same accomplished by WW_SELECTADDON tag for presentation/foil add-ons

-->

<WW_SELECTSOUND FOILID="${FID}" NAME="ISSOUND">

<INSERT NAME="${ISSOUND}"/>

</WW_SELECTSOUND>

<WW_SELECTADDON FOILID="${FID}" NAME="ISADDON">

<INSERT NAME="${ISADDON}"/>

</WW_SELECTADDON>

<hr>

<!-- WW_NOBULLETSIFGIF checks for existence of the foil image.

If the foil specified in FOILID attribute has no image, the element

contents will be parsed.

Because inside WW_NOBULLETSIFGIF there is a WW_FOILTEXT tag,

the table with foil text will be displayed if this foil has no image.

If foil has an image, the contents of WW_NOBULLETSIFGIF will be ignored.

(this tag should be named WW_IFNOGIF but it is named

WW_NOBULLETSIFGIF in accordance with original NPAC templates)

-->

<WW_NOBULLETSIFGIF FOILID="${FID}">

<WW_FOILTEXT FOILID="${FID}"/>

</WW_NOBULLETSIFGIF>

<a name="image">

<!-- WW_SELECTDISPLAYMODE inserts into variable with name given by NAME

attribute the preferred display mode of the foil.

With the following WW_IF, it acts in the same way as the original

NPAC {select=123} tag.

-->

<WW_SELECTDISPMODE FOILID="${FID}" NAME="QUERY"/>

<WW_IF CONDITION="%OR(%EQU(${QUERY},1),%EQU(${QUERY},2),%EQU(${QUERY},3))">

<WW_THEN>

<!-- WW_FOILIMAGE inserts image for foil given by FOILID

attribute. The presentation id: PARENTID will be later

used to determine formatting properties (properties,

different than the default, can

be defined on user, presentation, or foil level).

-->

<WW_FOILIMAGE FOILID="${FID}" PARENTID="${PID}"/>

</WW_THEN>

</WW_IF>

<hr>

<WW_NEXT FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsepimage.tdl" IMAGENAME="ww_next"/>

<WW_PREV FOILID="${FID}" PARENTID="${PID}" FILENAME="tempfoilsepimage.tdl" IMAGENAME="ww_prev"/>

<WW_LINK FILENAME="tempfullindex.tdl" ATTR="PID=${PID}">

<WW_IMAGE IMAGENAME="ww_up" FOILID="${FID}" PARENTID="${PID}"/>

</WW_LINK>

<!-- The following pair of tags inserts the signature of the current

foil/presentation.

First WW_DBSET takes the signature value form a database property

in context of the current user, presentation and foil.

PROPTYPE attribute specifies the type of the property

('overall' in case of signature), PROPNAME supplies the

database property name. The value of the property assigned to a variable

given by NAME attribute - here: SIG.

WW_INSERT inserts the value of the signature into the output text.

-->

<WW_DBSET NAME="SIG" PROPNAME="signature" PROPTYPE="OVERALL" FOILID="${FID}" PARENTID="${PID}"/>

<WW_INSERT NAME="${SIG}"/>

</WW_DOCUMENT>

 

5. Template file to navigate in foilworld tree

<?WWTEMPLATE>

<?XML VERSION="1.0" CACHE="NO"?>

<WW_DOCUMENT>

<!-- ?WWTEMPLATE and ?XML tags form the header for all template files.

CACHE attribute of the XML tag specifies whether the servlet should

cache the file or not.

-->

<!-- WW_CONNECT is a tag that establishes a connection to a database.

Connection string may be supplied in the CONNECTION attribute,

or if omitted (empty string) the default

connection string is taken from properties.txt file, which specific for

the template.

-->

<WW_CONNECT CONNECTION=""/>

<html>

<head>

<!-- WW_TITLEFOILWORLD is a tag that inserts the foilworld title into output text.

The foilworld is identified by the FWID attribute. The current value

of this attribute is taken here from the FWID variable.

This variable was set automatically by a servlet on the base of the URL

query parameter.

NOTE:

Every parameter passed within an URL is put into a variable of the same

name before a file is parsed. For instance, before parsing a file

referenced by an URL:

'file.tdl?A=1&B=3&C=one'

the following variables will be set:

A with value 1,

B with value 3, and

C with value 'one'.

All these variables are accessible within the file using ${variable_name} syntax.

-->

<title> Foilworld contents for <WW_TITLEFOILWORLD FWID="${FWID}"/> </title>

</head>

<!-- WW_BODYINDEX inserts a 'body' HTML tag with background image typical

for index files.

This tag should be reimplemented to take images from the database

-->

<WW_BODYINDEX/>

<h2><tt>Title for</tt> <WW_TITLEFOILWORLD FWID="${FWID}"/> </h2>

<hr>

<b><tt>Foilworlds in this foilworld </tt><b><p>

<!-- WW_FOILWORLDLOOP is a loop tag that for given foilworld ID (passed as FWID

attribute), parses its contents, setting for each loop pass a variable given by

NAME attribute.

This variable contains an identifier of a 'child' foilworld.

The loop is repeated as many times as many child foilworlds the

current foilworld contains.

With following WW_FOILWORLDLINK, which creates a HREF link to same

file but with child foilworld_id, it allows to create an 'index' of all

foilworlds contained by the current foilworld.

In this case the HREF link will have the form:

HREF="tempfoilworld.tdl?FWID=child_id_from_LOCALFWID_var&_

other_attributes_given_in_ATTR"

The target file can be changed using FILENAME attribute and additional

attributes may be suplied in the ATTR attribute

-->

<WW_FOILWORLDLOOP FWID="${FWID}" NAME="LOCALFWID">

<WW_FOILWORLDLINK FWID="${LOCALFWID}" FILENAME="tempfoilworld.tdl" ATTR=""/>

</WW_FOILWORLDLOOP>

<hr>

<b><tt>Presentations in this foilworld </tt><b><p>

<!-- The same as WW_FOILWORLDLOOP and WW_FOILWORLDLINK pair, but creates

a list of links to presentations instead of child foilworlds,

contained by a current foilworld.

Note that the filename in the FILENAME attribute was changed and points

to a full index file for presentation

-->

<WW_PRESENTATIONLOOP FWID="${FWID}" NAME="LOCALPID">

<WW_PRESENTATIONLINK PRESENTATIONID="${LOCALPID}" FILENAME="tempfullindex.tdl"

ATTR=""/>

</WW_PRESENTATIONLOOP>

</WW_DOCUMENT>

6. Template file to create and display index with links to foils