PixieEngine(TM) 1.2

NEW:

• Now supports Microsoft SQL Server 7 and above as datastore.
• PixieLink for PixieEngine now included, so immediately after setup, you can start test-driving with GUI and terminal interfaces.
• Scripting support:  PixieEngine is now programmable in VBSCRIPT, JSCRIPT or any other additional Windows scripting engine eg PERL
• XCommon object is an in-memory data store available to all programs and scripts in a user session.
• PixieEngine Personal Edition (2 user/JET datastore) is free for non-commercial, experimental, educational and personal use.

Chapter 1 - Overview (this document)
Introduction
VAR-programming overview and issues re possible directions.
WebServer / VBA/ COM Programming
DataStore overview.

Chapter 2 - Installing, configuring and test-running
To Install
Support files you may need.
Optional but recommended: download and installation of MySQL
After Setup - guide to your resulting PixieEngine folder.
Terminal emulator setup.
Suggested testing activities and guide to the example programs.

Chapter 3 - VAR programming
A tale of 2 servers: Socket or COM.
What you need: VB6 or VB5.
VB/PixieEngine Project organisation and Language notes.
How to emulate some common MV and DATABASIC practices.

Appendix - PixieEngine Functions
System Variables and Wide-Ranging Argument Conventions
Classical Terminal/Printer I/O, "IInput", "PPrint", "Crt"
File I/O "RRead", "WWrite" etc and the new "RReadTR"
ExecutePS
String and other utility functions eg "DCount", "Field", "OConv", "Locate"

PixieEngine configures suitable database engines, eg MySQL, to present their operations in the "MV" or "PICK-like" way. PixieEngine also provides a host programming environment in Visual Basic with a DATABASIC-like flavour. Other languages are also possible.
The core of "PixieEngine (TM)" is an "ActiveX" wrapper for the database engines: 'MySQL', 'MS SQL SERVER' and 'MS JET/ACCESS' with more connections in preparation.  While its core is "Object Oriented", PixieEngine also has a "Socket Server" component that enables it to support terminal emulation in the "Classical" way.
We mostly use MS Access/Jet .mdb files. as a lightweight prototyping demo and test alternative, but they also give you the  "linked table" or "mde project" capability to use a wider range of data stores eg FoxPro, Oracle.  Access/Jet also makes for an easy to setup download package. The download has sample data for both Access/Jet and MySQL and we anticipate that most of you will be able to try Access/Jet immediately whereas you need 2 additional downloads and setups to get a MySQL engine going. However MS Access is less effective at emulating MV than the true server daemons.  So please use MySQL  or MS SQL for any serious performance assessment.

What "Microsoft Access" does make possible is the wrapping of some of the PixieEngine functions into file "testpxe1.mdb" as VBA code. This means that "testpxe1.mdb" acts as a self-contained "quickie" demo of some of PixieEngine. You need "Access 97" or newer to open it. If reading this with internet access, click here to download testpxe1.zip (only 100K) .

Note sample data is fictional, especially the randomly generated prices.

When you purchase PixieEngine, it is supplied with:

• PixieMassage, for converting legacy DATABASIC programs
• PixieEditor, which can convert data from some classic MV engines.
• PxEngLink (based on our PixieLink), a GUI-capable front end which can also handle classical terminal emulation.  

Available separately is our GUI thin-client PixieLink.

There are 3 licensing levels for PixieEngine:

1. PixieEngine Personal Edition - no licence required and so free of charge.
   Restricted to JET/ACCESS datastore only and 2 users max.
2. PixieEngine Special Licence - economically-priced light-duty system.
   Restricted to JET/ACCESS datastore only, but we impose no limit on the number
   of users.  We rely on the JET/ACCESS limitations.  In practical terms this
   means a max of 5 simultanous heavy-demand users up to about 20 light-demand.
3. PixieEngine Full Industrial-Strength Edition.  Any datastore, no user limits.

Pricing of 2 and 3 is by negotiable quote for each situation and is usually a single price for unlimited use within a site or organisation with a support package built in. We price PixieEngine on a "fair value for money" principle.

PixieEngine's equivalent to DATABASIC is to program with Microsoft VB5 or VB6 by creating your app as an ActiveX .dll, instances of which get hosted inside PixieEngine's "UserPort" objects. We provide a template app to copy and adapt. In theory any Windows development environment that can talk to ActiveX objects should work as a VAR-Programming method, but we have not yet tried Java, Delphi etc ourselves.

VB5/6 has a very attractive editing and debugging environment. The obvious question is "whoa, big change from DATABASIC" but VB is a very malleable system and we have done 2 things to bring it close to DATABASIC:

1. Provided the option of retaining the DATABASIC procedural model, ie Input and Output can still be achieved within programs by IInput, Crt and PPrint, and you do NOT need to follow the usual VB client-side "event-driven model" of 1-user-action = 1-complete-routine-run.
2. Provided a library of DATABASIC-emulating functions
   eg EXTRACT, RREPLACE, OOPEN, CCLOSE, RREAD, WWRITE
   RREADU, RREADTR(new idea, see reference), RREADV, RREADVU,
   WWRITEU, WWRITEV, WWRITEVU, RELEASE, OCONV,
   TTAG (equivalent of @), FIELD, DCOUNT, LOCATE, INDEX,
   MATCHES and growing ...

eg DATABASIC

OPEN Cust TO File.Cust ELSE
  CRT 'Cannot open file "Cust".' 
  STOP
END
** dynamic variables
A<3,4> = B
C = D<1,2,3>

translates to VB

If Not OOpen(Cust, File_Cust) Then
  Crt "Cannot open file ""Cust""."
  Exit Sub
End If
'* PixieEngine supports 
'* "dynamic variables"
A = RReplace(A, 3, 4, B)
C = Extract(D, 1, 3, 3)

We have written a utility "PixieMassage" which does such conversions automatically with a useful success rate. Note that VB and the DataStores have their own reserved purposes for "dot" and "hyphen" operators. So in most cases, DATABASIC and TCL file, variable and routine names like "File.Cust" and "BP.WEB" need to change eg to "File_Cust" and "BP_WEB".

"PixieEngine" handles a subset of PICK emulation. Some current challenges are:

• Handling GOTO into and out of INCLUDEd code. At present, setting common variables and values in INCLUDEs is no problem, the Visual Basic "Procedure Header" with Public variables does much the same thing.
  But you do need to convert coded processes to subroutines.
• Handling T-correlatives. These usually need to become SQL sentences featuring "INNER JOIN" or "LEFT JOIN", but multi-step programs looping through "ExecutePS" statements may also be needed.

The PixieEngine components with their functions can be accessed directly from IIS Webserver ASP scripts and any other COM-programming eg the VBA programming facility built into Microsoft Word, Access etc.

The approach is very much the same as outlined above under VAR-programming, except that the object-oriented rule of "1-user-action = 1-complete-routine-run" applies. The other difference is that you do not need to buy VB6. MS Word etc include the VBA language and the IIS Webserver with VBSCRIPT is a free add-on to Windows.

Example ASP SCRIPT fragment equivalent to above VAR DATABASIC and VB examples:

Set P = Server.CreateObject("PixieEngine.Port")
Set F = Server.CreateObject("PxEngFns.Functions")
'** Login user "jeffrey" with a password of "biscuit"
Call P.Execute("jeffrey")
Call
P.Execute("biscuit")
'
If P.OOpen(Cust, File_Cust) = False Then
  Response.Write "Cannot open file ""Cust""."
  Response.End
End If
'** PixieEngine supports dynamic variables"
A = F.RReplace(A, 3, 4, B)
C = F.Extract(D, 1, 3, 3)
…

It is also possible to program Webserver Apps in the classical procedural style eg with i/o via CRT/PPRINT and IINPUT.  But you need to include a "buffer zone" between PixieEngine's procedural BASIC world and the strictly event-driven world of IIS.  This can be done via our other product PixieWeb or with a supplied component PxEngWeb.

"Accounts" are emulated by "databases". In MySQL these are separate subfolders
off MySQL folder "data"
In "Access/Jet" they are separate .mdb files in folder
c:\Program Files\PixieEngine\JetMDB\

"Files"( aka "Tables") feature:

• Attribute labels ( aka "Field Names" ) of A0, A1, A2, A3,...
• A0 is defined by default as a 25-character indexed "Primary Key"
  so it simulates the MV "ItemID"
• MySQL - all other fields are made "LONG VARCHAR", ie they
  can store strings of any length. We have discovered that MySQL
  delivers exceptionally good LONG VARCHAR performance
  compared to other RDBMSs.
  Access/Jet - default of "MEMO" ie "LONG VARCHAR" but
  performance with these is limited, so whenever possible fields are
  re-defined to fixed length of 1.5 times the longest known value.
• DataStores do NOT share the PICKetc capability of increasing the
  number of attributes in an Item at any time. The expected number of attributes must be declared when creating the file/table and if you need more later, you need to do
  "ALTER TABLE ...MODIFY ..." or similar.
  NOTE our TCL function "CREATE FILE" where the number argument
  may look like an MV "modulus" but is really the number of attributes
  allowed for: eg " CREATE-FILE PORD 55 D"
• Both DataStores work with Microsoft Access as the front end program, so much so that we have provided only a limited TCL environment.  We intend that most TCL-admin-like tasks eg queries, ed, would be done via the Access front end. (NOTE that the "Access" visible front end program is a separate component to its associated "Access/Jet" data storage method. The visible front end is applicable to and useful for MySQL)
• Dictionaries are optional. Where used they are identified by "_dict"
  added to the file name eg "prod" has a dictionary "prod_dict".
• "md" files currently support their "pointer to compiled program" function with more emulation planned.
• "dm" currently provides the "user" file with similar behaviour to MV equivalents.

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