best practices in oo lotus script final draft

8/2/2019 Best Practices in OO Lotus Script Final Draft

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BP107

Best Practices for ObjectOrientated Lotusscript

BP107

Best Practices for ObjectOrientated Lotusscript

Bill Buchan

Director, HADSLPremier Business Partner

Bill Buchan

Director, HADSLPremier Business Partner


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AgendaAgenda

Why use Object Orientated Methodologies?

OO Basics in Script

Demo OO application Directory Compare

Extend or Encapsulate ?

Large OO projects

Pitfalls and Tricks

Summary and questions


OO Basics in Script



Large OO projects

Pitfalls and Tricks



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What is OO Programming?What is OO Programming?

Its a way of writing large, complex systems in amore intuitive manner

The core assumptions are: Most objects will represent actors or processes in a

business problem

You do not need to know how an object is implemented inorder to use it. (Information Hiding)

Its been in Lotusscript since its inception.

Its a different way of breaking down problems. Compared to structured programming

It requires more thought during architecture

It requires less work during implementation (in a wellarchitected system)

Its a way of writing large, complex systems in amore intuitive manner

The core assumptions are: Most objects will represent actors or processes in a

business problem

You do not need to know how an object is implemented inorder to use it. (Information Hiding)

Its been in Lotusscript since its inception.

Its a different way of breaking down problems. Compared to structured programming

It requires more thought during architecture

It requires less work during implementation (in a wellarchitected system)


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Why use OO Methodologies ?Why use OO Methodologies ?

Maintainability & Robustness

Small code sequences are easier to maintain

Code hiding lends to better componentisation anddesign

Loose Coupling is better than tight coupling.

Classes can be tested in a stand-alone basis beforeintegration with other components. It can help youtest sooner (and should be considered best practice)

Promotes Re-use

The holy grail of software development Standard business components can be re-used.

Look at the future

Java anyone ?

Maintainability & Robustness

Small code sequences are easier to maintain

Code hiding lends to better componentisation anddesign

Loose Coupling is better than tight coupling.

Classes can be tested in a stand-alone basis beforeintegration with other components. It can help youtest sooner (and should be considered best practice)

Promotes Re-use

The holy grail of software development Standard business components can be re-used.

Look at the future

Java anyone ?


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How to use OO Methodologies ?How to use OO Methodologies ?

Define a class Class fredpublic mystring as String

sub new()

me.myString = Hello Worldend sub

end class

Create one or instances of this class in

memory Dim myFred as new Fred()print myFred.myString

Define a class Class fred

public mystring as String

sub new()

me.myString = Hello Worldend subend class

Create one or instances of this class inmemory Dim myFred as new Fred()print myFred.myString


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Some OO GeneralisationsSome OO Generalisations Its difficult to use - Not at all.

Its a steep learning curve No

There is no benefit.

Untrue. From a medium to large scale project, getting it

right from the start means more code reuse, more robustapplications, and less effort.

There is one class for each item in a system

Probably not.

Try not to be too prescriptive in any architecture. It takes a couple of projects before you get it.

This is probably true. The oo moment.

Its difficult to use - Not at all.

Its a steep learning curve No

There is no benefit.

Untrue. From a medium to large scale project, getting it

right from the start means more code reuse, more robustapplications, and less effort.

There is one class for each item in a system

Probably not.

Try not to be too prescriptive in any architecture. It takes a couple of projects before you get it.

This is probably true. The oo moment.


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AgendaAgenda


OO Basics in Script



Large OO projects

Pitfalls and Tricks



OO Basics in Script



Large OO projects

Pitfalls and Tricks



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How to use OO within Lotusscript ?How to use OO within Lotusscript ?

Use Classes to define objects.

Use new and delete to create instances of classes

Think of notesDatabase

They bundle together

members (properties) Functions and Subs (methods)

Classes can be based on other classes

In which case they inherit all the properties and

functions of the parent class More on this later

Use Classes to define objects.

Use new and delete to create instances of classes

Think of notesDatabase

They bundle together

members (properties) Functions and Subs (methods)

Classes can be based on other classes

In which case they inherit all the properties and

functions of the parent class More on this later


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OO BasicsOO Basics

Classes are defined by wrapping them with

class [as ]

end class

The classes are all defined in the declarations section of aLotusscript code sequence.

Remember. R5 64 limit. R6 bigger. ND7 - Best

When a class is constructed

The sub new() function (the constructor) is calledfor this class, and all its parent-classes

The top-most parent class constructor is called firstWhena class is deleted

The sub delete() (the destructor) function is called

You cannot extend subclasses from base notes classes.

Classes are defined by wrapping them with

class [as ]

end class

The classes are all defined in the declarations section of a

Lotusscript code sequence.

Remember. R5 64 limit. R6 bigger. ND7 - Best When a class is constructed

The sub new() function (the constructor) is calledfor this class, and all its parent-classes

The top-most parent class constructor is called firstWhena class is deleted

The sub delete() (the destructor) function is called

You cannot extend subclasses from base notes classes.


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OO BasicsOO Basics

You can define items within a class as Public anything else can use this property or method Private only the class itself (or any subclasses) can use

this property or method)

You can extend or subclass classes For instance, the class Animal could be extended by

class dog, which is a more precise version of the class

Class dog shares and re-uses all properties andmethods from Animal.

Class dog may OVERRIDE methods within animal Class dog may provide MORE properties and methods

than class ANIMAL.

You can define items within a class as Public anything else can use this property or method

Private only the class itself (or any subclasses) can usethis property or method)

You can extend or subclass classes For instance, the class Animal could be extended by

class dog, which is a more precise version of the class

Class dog shares and re-uses all properties andmethods from Animal.

Class dog may OVERRIDE methods within animal Class dog may provide MORE properties and methods

than class ANIMAL.


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Example: Animal and DogExample: Animal and DogClass animal

Private myName as String

Sub new()me.myName = Animal

End sub

Public function getName() as String

getName = me.myName

end function

Public function getSpecies() as String

getSpecies = Animal

End function

End class

Class Dog as AnimalPublic masterName as String

sub new()

me.myName = Dog

end sub

End class

Class animal

Private myName as String

Sub new()me.myName = Animal

End sub

Public function getName() as String

getName = me.myName

end function

Public function getSpecies() as String

getSpecies = Animal

End function

End class

Class Dog as AnimalPublic masterName as String

sub new()

me.myName = Dog

end sub

End class

ConstructorConstructor

Private Member

Public Member

Overridden Constructor

Dog inherits from class

Animal


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OO Basics some best practicesOO Basics some best practices

Each class contained in a different script libraryDont expose your internal properties

Declare them as private!

Use Me. to resolve ambiguity

You can use property get & set constructs. Functions that look like class properties

Advise against it

Keep the classes small. Large classes mean that you should split them up

that you probably aren't re-using things as much as youcan

Always Architect before optimising

Each class contained in a different script library

Dont expose your internal properties Declare them as private!

Use Me. to resolve ambiguity

You can use property get & set constructs. Functions that look like class properties

Advise against it

Keep the classes small. Large classes mean that you should split them up

that you probably aren't re-using things as much as youcan

Always Architect before optimising


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AgendaAgenda


OO Basics in Script



Large OO projects

Pitfalls and Tricks



OO Basics in Script



Large OO projectsPitfalls and Tricks



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OO Basics. The Person ClassOO Basics. The Person Class

Class Person

Public PersonName as NotesName

Public DominoDomain as String

Private UNID as String

sub new(doc as notesDocument)

set me.PersonName = new NotesName(doc.FullName(0))

me.DominoDomain = doc.Domain(0)

me.UNID = doc.UniversalIDend sub

End class

Class Person

Public PersonName as NotesName

Public DominoDomain as String

Private UNID as String

sub new(doc as notesDocument)

set me.PersonName = new NotesName(doc.FullName(0))

me.DominoDomain = doc.Domain(0)

me.UNID = doc.UniversalIDend sub

End class


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So how do I use this ?So how do I use this ?

Use class:personClass

Dim P as new person(doc)

Print This persons name is: &

P.personName.Abbreviated

Use class:personClass

Dim P as new person(doc)

Print This persons name is: &

P.personName.Abbreviated

Library names are casesensitive on non-wintel

platforms!


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AgendaAgenda


OO Basics in Script



Large OO projects

Pitfalls and Tricks



OO Basics in Script






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Extend or Encapsulate ?Extend or Encapsulate ?

Remember: Extending class takes a class, makes a new class from it, but inherits

all properties and methods

You can override original class methods

You cannot overload methods (as Java can) You can add new methods

And of course you can extend to any depth

Encapsulating a class

makes a new class more useful by using otherclasses within it

Remember: Extending class

takes a class, makes a new class from it, but inheritsall properties and methods

You can override original class methods

You cannot overload methods (as Java can) You can add new methods

And of course you can extend to any depth

Encapsulating a class

makes a new class more useful by using otherclasses within it


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Make this more useful by EncapsulationMake this more useful by Encapsulation

Class PersonCollectionprivate people list as Person

public sub addPerson(P as Person)

set me.people(P.PersonName.Abbreviated) = P

end sub

public function findPerson(userName as String) as Person

set findPerson = nothing

if (isElement(me.people(userName))) then

set findPerson = me.people(userName)end if

end function

End class

Class PersonCollectionprivate people list as Person

public sub addPerson(P as Person)

set me.people(P.PersonName.Abbreviated) = P

end sub

public function findPerson(userName as String) as Person

set findPerson = nothing

if (isElement(me.people(userName))) then

set findPerson = me.people(userName)end if

end function

End class


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So how do I use personCollection?So how do I use personCollection?Dim PC as new PersonCollection

Dim doc as NotesDocumentSet doc = myView.getFirstDocument

While Not (doc is nothing)

dim P1 as new Person(doc)

call PC.addPerson(P1)

set doc = myView.getnextDocument(doc)Wend

Dim P as person

Set P = PC.findPerson(Joe Bloggs/Acme)If Not (P is nothing) then

print found person: & P.PersonName.Abbreviated

End if

Dim PC as new PersonCollection

Dim doc as NotesDocumentSet doc = myView.getFirstDocument

While Not (doc is nothing)

dim P1 as new Person(doc)

call PC.addPerson(P1)

set doc = myView.getnextDocument(doc)Wend

Dim P as person

Set P = PC.findPerson(Joe Bloggs/Acme)If Not (P is nothing) then

print found person: & P.PersonName.Abbreviated

End if


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Lets improve PersonCollectionLets improve PersonCollectionClass PersonCollection

public Function loadAllDocsInView(mV as NotesView)

dim doc as NotesDocument

set doc = mV.getFirstDocument

while Not (doc is nothing)

dim P as new Person(doc)

call me.addPerson(P)

set doc = mV.getNextDocument(doc)

wend

end function

end class

Class PersonCollection

public Function loadAllDocsInView(mV as NotesView)


set doc = mV.getFirstDocument

while Not (doc is nothing)dim P as new Person(doc)

call me.addPerson(P)


wend

end function

end class


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New example code.New example code.


Call PC.loadAllDocsInView(myView)

.

Dim P as person

Set P = PC.findPerson(Joe Bloggs/Acme)

If Not (P is nothing) then

print found person: &P.PersonName.Abbreviated

End if


Call PC.loadAllDocsInView(myView)

.

Dim P as person

Set P = PC.findPerson(Joe Bloggs/Acme)

If Not (P is nothing) then

print found person: &P.PersonName.Abbreviated

End if


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Now lets use PersonCollectionNow lets use PersonCollection

Well use this example class to quickly comparetwo domino directories.

Open both directories, and views in each database

Create a new PersonCollection from each view.

Iterate through the first PersonCollection, and checkto see that this person is in the second view.

And vice versa.

Why does this help ?

We only load the Person Documents once

We can further improve this by:

Using NotesViewEntryCollection instead of notesView

Well use this example class to quickly comparetwo domino directories.

Open both directories, and views in each database

Create a new PersonCollection from each view.

Iterate through the first PersonCollection, and checkto see that this person is in the second view.

And vice versa.

Why does this help ?

We only load the Person Documents once

We can further improve this by:

Using NotesViewEntryCollection instead of notesView


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An interesting observationAn interesting observation


public Function loadAllDocsInView(mV as Variant)


set doc = mV.getFirstDocumentwhile Not (doc is nothing)


me.addPerson(P)


wend

end function

end class


public Function loadAllDocsInView(mV as Variant)


set doc = mV.getFirstDocumentwhile Not (doc is nothing)


me.addPerson(P)


wend

end function

end class


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Demo Directory Comparison ToolDemo Directory Comparison Tool


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AgendaAgenda


OO Basics in Script






OO Basics in ScriptDemo OO application Directory Compare





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Large OO ProjectsLarge OO Projects

How to design large OO projects

Consider various approaches, and iteratetowards a good OO architecture.

Good design and architecture is better than

codingUse skeleton classes to mimic behaviour

Allows early integration

Allows you to finalise class structure quickly

Unit test each class.

And keep unit testing them to prevent regressions

How to design large OO projects

Consider various approaches, and iteratetowards a good OO architecture.

Good design and architecture is better than

codingUse skeleton classes to mimic behaviour

Allows early integration

Allows you to finalise class structure quickly

Unit test each class.

And keep unit testing them to prevent regressions


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Large OO Projects Large OO Projects

Its *never* completely correct Beware tightly bound mutually dependant classes!

Remember that specifications change over time.

Architect for clarity and maintenance.

Performance is an implementation consideration!

If you have to change class methods frequently You are exposing weaknesses in the design phase

You are open to regression errors

Once methods behaviour are finalised, dont changethem! Add more methods, but dont modify.

You may have to do several OO applicationsbefore you get it.

Its *never* completely correct Beware tightly bound mutually dependant classes!

Remember that specifications change over time.

Architect for clarity and maintenance.

Performance is an implementation consideration!

If you have to change class methods frequently You are exposing weaknesses in the design phase

You are open to regression errors

Once methods behaviour are finalised, dont changethem! Add more methods, but dont modify.

You may have to do several OO applicationsbefore you get it.


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AgendaAgenda


OO Basics in Script











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Pitfalls Fixup Time on LoadPitfalls Fixup Time on LoadRemember, LotusScript is a p-code compiled,

interpreted language Similar to Java

Lotusscript has some loose data constructs:

This means that Fixup Time is significant.

What is fixup time ? The time taken to load all modules, and to resolve all variables. In

traditional compiled programs, this was performed by the linker atexecutable build time.

How does this affect me ?

The more complex your applications, the longer it takes almostgeometrically to load. (this applies to ALL code, not just classes)

Example: 20 classes 4 seconds load time. 120 classes 145seconds load time.

Remember, LotusScript is a p-code compiled,

interpreted language Similar to Java

Lotusscript has some loose data constructs:

This means that Fixup Time is significant.

What is fixup time ? The time taken to load all modules, and to resolve all variables. In

traditional compiled programs, this was performed by the linker atexecutable build time.

How does this affect me ?

The more complex your applications, the longer it takes almostgeometrically to load. (this applies to ALL code, not just classes)

Example: 20 classes 4 seconds load time. 120 classes 145seconds load time.


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Fixup time vs Complexity

Complexity

Time(Seconds)

Fixup time vs Complexity

Complexity

Time

(Seconds)

Fixup time ?Fixup time ?


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How to code around itHow to code around it

Fixup time doesnt have significant impactbefore 20+ classes and/or script libraries (in myexperience) My Example: 120+ classes 145 seconds to load.

Use loose binding instead of tight binding. Use Variants to hold and pass classes

Use Dynamic Loading to instantiate classes

After implementation, same 120+ classes 15seconds.

Downside. No more type checking! Demands programming discipline and rigour!

Fixup time doesnt have significant impact

before 20+ classes and/or script libraries (in myexperience) My Example: 120+ classes 145 seconds to load.

Use loose binding instead of tight binding. Use Variants to hold and pass classes

Use Dynamic Loading to instantiate classes

After implementation, same 120+ classes 15seconds.

Downside. No more type checking! Demands programming discipline and rigour!


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Dynamic Loading referenceDynamic Loading reference

Dynamic loading is a technique outlined inRedbook

Performance Considerations for DominoApplications

SG24-5602

Buried in Appendix B, Page 243

Numerous Gary Devendorf Web Servicesexamples

Dynamic loading is a technique outlined inRedbook

Performance Considerations for DominoApplications

SG24-5602

Buried in Appendix B, Page 243

Numerous Gary Devendorf Web Servicesexamples


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Dynamic Loading ExampleDynamic Loading ExamplePrivate P as variant This HAS to be global!

Function createOtherClass_(scriptName as String, className as String) as variant

Dim exString as String

exString = | Use | & scriptName & |

sub initialize

Set P = new | & className & |Factory &end sub |

Execute exString Now run the code in exString

Set createOtherClass = P

End sub

Sub DynamicLoadingExample

dim myClass as variant

set myClass = createotherClass(class:fred, fred)

End sub

Private P as variant This HAS to be global!

Function createOtherClass_(scriptName as String, className as String) as variant

Dim exString as String

exString = | Use | & scriptName & |

sub initialize

Set P = new | & className & |Factory &end sub |

Execute exString Now run the code in exString

Set createOtherClass = P

End sub

Sub DynamicLoadingExample

dim myClass as variant

set myClass = createotherClass(class:fred, fred)

End sub

This string containsLotusscript code


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Script library class:fred looks like:Script library class:fred looks like:

Class FredFactory

Public Function produce As Variant

Set produce = New Fred

End Function

End Class

Class Fred

End class

Class FredFactory

Public Function produce As Variant

Set produce = New Fred

End Function

End Class

Class Fred

End class

The Factory Version of this class

exists only to create a newinstance of the main class

There are no constructor arguments

being passed to class fred. This willhave to be changed if you choose to add

constructor arguments.


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Dynamic Loading OO ArchitectureDynamic Loading OO Architecture

Always have one class that knows how toconstruct the rest WITHOUT using the usedirective.

A Factory class, for instance.

You dont have to dynamically load ALL classes. Common classes such as log or config are

always normally resident

You can dynamically load different classes.

Based on Notes/Domino version, Platform, Data

Using one dynamic load function means you have touse the same signature on the class constructor

Always have one class that knows how toconstruct the rest WITHOUT using the usedirective.

A Factory class, for instance.

You dont have to dynamically load ALL classes. Common classes such as log or config are

always normally resident

You can dynamically load different classes.

Based on Notes/Domino version, Platform, Data

Using one dynamic load function means you have touse the same signature on the class constructor


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Dynamic Loading OO ExampleDynamic Loading OO Example

Request

LogFactory

Configuration

User Create v6

User Create UIUser Create Profile

User Create v5


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Compilation WoesCompilation Woes Expect Compilation Complexity.

For instance, consider the fairly simple classstructure

Expect Compilation Complexity.

For instance, consider the fairly simple classstructure

Class Factory

Agent 1

Class Factory


Agent 4Agent 3Agent 2Agent 1


Agent 4Agent 2Agent 1


Routines:Examples

Class Person


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Compilation WoesCompilation Woes Change a subclass deep in the inheritance hierarchy and you

will probably:

See Server Console AMGR message or client dialog: 11/23/2004 12:03:03 PM Agent '(Blah)' error:

Error loading USE or USELSX module: cl_event_v2

Error %s

Why ? The signature of the subclass has changed How to resolve ?

Tools, Compile all Lotusscript.

Similar to Java. Most java IDEs will rebuild all whensignificant change is spotted.

Dynamic loading completely sidesteps thisissue

Change a subclass deep in the inheritance hierarchy and youwill probably:

See Server Console AMGR message or client dialog: 11/23/2004 12:03:03 PM Agent '(Blah)' error:

Error loading USE or USELSX module: cl_event_v2

Error %s

Why ? The signature of the subclass has changed How to resolve ?

Tools, Compile all Lotusscript.

Similar to Java. Most java IDEs will rebuild all whensignificant change is spotted.

Dynamic loading completely sidesteps thisissue


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Code HidingCode Hiding

The Hide Design database

property can sometimes be toorestrictive.

Should all of your commercial codebe in script libraries, then:

Find the script librarys design document

Replace item ScriptLib with some text such as MyName, 2004

The end-user cannot recompile the library and cannotsee your code.

Warning. No way back (obviously). So do this on yourBUILD copies of templates, not your developmenttemplates

The Hide Design database

property can sometimes be toorestrictive.

Should all of your commercial codebe in script libraries, then:

Find the script librarys design document

Replace item ScriptLib with some text such as MyName, 2004

The end-user cannot recompile the library and cannotsee your code.

Warning. No way back (obviously). So do this on yourBUILD copies of templates, not your developmenttemplates


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AgendaAgenda












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SummarySummary

OO is a simple, pain-free way of building andmaintaining large Domino Projects.

OO should be part of your toolset duringapplication design

Lotusscript can do large, serious and complexOO projects

OO is a simple, pain-free way of building and

maintaining large Domino Projects.

OO should be part of your toolset duringapplication design

Lotusscript can do large, serious and complexOO projects


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Related Sessions and ResourcesRelated Sessions and ResourcesRedbook: Performance Considerations for Domino

Applications Search for SG24-5602 at http://www.lotus.com/redbooks

Notes.net Article: Using the object-orientated features of Lotusscript

by Bruce Perry, from October 2001.Dev.kaangard.net

http://dev.kanngard.net/dev/home.nsf/ArticlesByTitle/LSClass.html

OpenNTF Check out OpenDom by Alain H Romedenne

http://www.openntf.org

Redbook: Performance Considerations for DominoApplications Search for SG24-5602 at http://www.lotus.com/redbooks

Notes.net Article: Using the object-orientated features of Lotusscript

by Bruce Perry, from October 2001.Dev.kaangard.net

http://dev.kanngard.net/dev/home.nsf/ArticlesByTitle/LSClass.html

OpenNTF Check out OpenDom by Alain H Romedenne http://www.openntf.org


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Questions?Questions?

Please fill out your evaluations

Remember you can ask me more questions in:

Toucan 2 for the next hour

Guru-Pazoola in the Swan at 10:30am

all Best Practices Speakers will be there. By sending me mail to Bill at BillBuchan.com

Check out our product iDM

http://www.hadsl.com

Thanks for coming!

Please fill out your evaluations

Remember you can ask me more questions in:

Toucan 2 for the next hour

Guru-Pazoola in the Swan at 10:30am

all Best Practices Speakers will be there. By sending me mail to Bill at BillBuchan.com

Check out our product iDM

http://www.hadsl.com

Thanks for coming!