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The talk will cover the use of decision tables in a variety of programming languages and software products and follow the development from simple Condition/Action tables to those with Initial Action and Multi-condition sections. This will include a brief history of the use of decision tables in IT from the 1970’s to present day. Table structures and rule formats used will be shown. The speaker will cover the topics of rule redundancy, rule reduction and optimisation as well as bit masking techniques for runtime evaluation, and demonstrate the importance of relevance testing. Examples of code will be used to show shortcut compact coding techniques and comparison with simple truth logic. There will be an explanation of the benefits and downsides of tools which use interpretive execution of decision table logic and those which use tokenised or fully compiled execution. Examples of program code and complex logic coding will be given and comparison made with “conventional” programming languages, which will demonstrate that Decision Tables can be used not just as visual representations of complex logical processing but also as a practical and efficient programming tool. A summary of current programming and application development tools which use decision tables will be given, and the speaker will discuss future developments and techniques that will allow decision table structured and expressed logic to be incorporated in other programming languages.
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rapidgen.com rapidgen.com
Howard Rogers Director Technical Support
Decision Tables as a
Programming tool
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Agenda
• A brief history
• Decision table structures
• Rule formats
• Rule redundancy, reduction and optimisation
• Relevance testing
• Some practical examples
• Current examples of use
• Future developments
• Questions and Answers
2
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Speaker
• Statistics & Operation Research
• UK National Health Service
• 35 years IT
• Decision table based languages and compilers
• Query & reporting tools
• Generic file & database access
• Brief interlude with RTPI
• Technical support
3
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History • NASA
• Morgan Crucible – LITA – List &Tabulate
• TABN for ICL 1900 series mainframes
• (DE)TAB-360 for IBM System/360
• UNITAB for UNIVAC
• HTAB for Honeywell
• TAB-11 for RSTS/E on PDP-11
• FTL6/DTPL for ICT 1900 series
• RPL-11 for RT-11, RSTS/E, RSX-11 on PDP-11
• RPL-3 for IBM System/3
• Filetab-D for x86 and PDP-11, OpenVMS VAX
• FPL - IBM PCs and compatibles.
• RPL, Rapid-Expert and expertGenius extended syntax for Microsoft
Windows, Unix, Linux and OpenVMS,VAX, Alpha & Itanium
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History
• Excel – query tables
• COPE – Translate DTs to COBOL
• LogicGEM – Translate to BASIC,C, C++, FORTRAN, Pascal etc etc
• CCIDE – Pre-processor for BASIC, JAVA, CC, C++, BASH, QB, VB,
and EX(euphoria)
• Silk (Simple In-line Logic Kompiler) converting decision tables to
Cobol code and vice versa.
• PASPREP – Pascal preprocessor
• Many many others
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Decision table structure
• Conditions
• Actions
• Condition rules
• Action rules
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Single Condition Decision Table
Condition Stubs Rules
Action Stubs Actions
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Quantity > 100 Y N
Apply 20% Discount X -
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Decision Tables
Horizontal vs Vertical Condition Stubs Action Stubs
Rules Actions
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Quantity > 100 Apply 20% Discount
Y N
X -
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Multiple Single Decision Table
Condition Stubs Rules
Action Stubs Actions
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Quantity > 100 Y Y N N
Cash payment Y N Y N
Apply 20% Discount X - - -
Apply 10% Discount - X - -
Apply 5% Discount - - X -
No discount - - - -
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Multiple Condition DTs
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• Complete True/False Y N require
2^Conditions rules
• 3 Conditions – 8 rules
• 4 Conditions – 16 rules
• etc
• Use of “-” to reduce completeness
• Practical limit 32
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Five Conditions – One rule
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Initially no discount
Quantity > 100 Y -
Cash payment Y -
Credit_check Y -
Product type is laptop Y -
Employee N -
Apply 5% Discount X -
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Multiple Section Decision Table
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Quantity > 100 Y Y N N
Cash payment Y N Y N
Apply 20% Discount X - - -
Apply 10% Discount - X - -
Apply 5% Discount - - X -
No discount - - - -
Discount_amount < $1 Y -
No discount X -
Discount amount > $1000 Y -
Set discount $1000 X -
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Simplifying Decision Tables 1
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1 2 3 4 5 6 7 8
Credit limit exceeded
Y Y Y Y N N N N
Cash payment Y Y N N Y Y N N
Special clearance Y N Y N Y N Y N
Accept order X X X - X X X X
Reject Order - - - X - - - -
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Simplifying Decision Tables 2
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1&2 3 4 5 6 7 8
Credit limit exceeded
Y Y Y N N N N
Cash payment Y N N Y Y N N
Special clearance - Y N Y N Y N
Accept order X X - X X X X
Reject Order - - X - - - -
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Simplifying Decision Tables 3
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1&2 3 4 5&6 7&8
Credit limit exceeded
Y Y Y N N
Cash payment Y N N Y N
Special clearance - Y N - -
Accept order X X - X X
Reject Order - - X - -
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Simplifying Decision Tables 4
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1&2 3 4 567&8
Credit limit exceeded
Y Y Y N
Cash payment Y N N -
Special clearance - Y N -
Accept order X X - X
Reject Order - - X -
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Simplifying Decision Tables 5
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4 123567&8
Credit limit exceeded
Y ELSE
Cash payment N -
Special clearance N -
Accept order - X
Reject Order X -
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Optimising Decision Tables
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1 2 3 4 5 6 7 8
Credit limit exceeded
Y Y Y Y N N N N
Cash payment Y Y N N Y Y N N
Special clearance Y N Y N Y N Y N
Accept order X - X - X X X X
Reject Order - X - X - - - -
2&4 123567&8
Credit limit exceeded
Y ELSE
Special clearance N -
Accept order - X
Reject Order X -
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ELSE Rule
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4 123567&8
Credit limit exceeded
Y ELSE
Cash payment N -
Special clearance N -
Accept order - X
Reject Order X -
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Simplifying Decision Tables –
Extended entry
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TRANSKEY GT MASTKEY Y - - - ELSE
TRANSKEY EQ MASTKEY - Y Y - -
TRANSKEY LT MASTKEY - - - Y -
TRANSTYPE = “I” - - - Y -
TRANSTYPE = “D” - - Y - -
TRANSTYPE = “A” - Y - - -
CALL PROCESS_MATCH - X - - -
CALL PROCESS_MISS - - X - -
CALL PROCESS_ADD - - - X -
CALL NEXT_TRANS - X X X -
CALL NEXT_MAST X X X - -
REPEAT X X X X -
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Simplifying Decision Tables –
Extended entry
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TRANSKEY ? MASTKEY > = = < ELSE
TRANSTYPE = “?” - A D I -
CALL PROCESS_? - MATCH MISS ADD -
CALL NEXT_TRANS - X X X -
CALL NEXT_MAST X X X - -
REPEAT X X X X -
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Ambiguity or Multi-ruling?
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Set discount
Initialise DISCOUNT_PERC
Cash payment Y - - -
Special offer - Y - -
Good credit history - - Y -
DISCOUNT_PERC + ? 5 10 2 -
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Code generation 1
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|--------------------------------------------------|
|--------------------------------------------------|
|# |STATEMENT 1 2 3 4 5 6 7 8 |
|--------------------------------------------------|
|C1 |Cash payment |y |y |y |y |n |n |n |n |
|C2 |Special offer |y |y |n |n |y |y |n |n |
|C3 |Good credit history |y |n |y |n |y |n |y |n |
|==================================================|
|A1 |Discount initialise | | | | | | | | |
|A2 |Discount + 5 |X |X |X |X | | | | |
|A3 |Discount + 10 |X |X | | |X |X | | |
|A4 |Discount + 2 |X | |X | |X | |X | |
|--------------------------------------------------|
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Generation – Nested If/else 1
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{ if ((Cash payment)) { if ((Special offer)) { if ((Good credit history)) { /* rule 1 */ Discount + 5; Discount + 10; Discount + 2; } else { /* rule 2 */ Discount + 5; Discount + 10; } } else { if ((Good credit history)) { /* rule 3 */ Discount + 5; Discount + 2; } else { /* rule 4 */ Discount + 5; } } } else {
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Generation – Nested If/else 2
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if ((Special offer)) { if ((Good credit history)) { /* rule 5 */ Discount + 10; Discount + 2; } else { /* rule 6 */ Discount + 10; } } else { if ((Good credit history)) { /* rule 7 */ Discount + 2; } else { /* rule 8 */ } } } }
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Generation – Case Switch 1
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{ if ((Cash payment)) { if ((Special offer)) { if ((Good credit history)) { rule_number = 1; } else { rule_number = 2; } } else { if ((Good credit history)) { rule_number = 3; } else { rule_number = 4; } } }
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Generation – Case Switch 2
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else { if ((Special offer)) { if ((Good credit history)) { rule_number = 5; } else { rule_number = 6; } } else { if ((Good credit history)) { rule_number = 7; } else { rule_number = 8; } } }
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Generation – Case Switch 3
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switch (rule_number) { case 1: Discount + 5; Discount + 10 ; Discount + 2; break; case 2: Discount + 5; Discount + 10; break; case 3: Discount + 5; Discount + 2; break; case 4: Discount + 5; break;
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Generation – Case Switch 4
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case 5: Discount + 10; Discount + 2; break; case 6: Discount + 10; break; case 7: Discount + 2; break; case 8: break; }
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Generation – Rule List 1
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{ if ( ((Cash payment)) && ((Special offer)) && ((Good credit history)) ) { Discount + 5; Discount + 10; Discount + 2; } if ( ((Cash payment)) && ((Special offer)) && (!(Good credit history)) ) { Discount + 5; Discount + 10; } if ( ((Cash payment)) && (!(Special offer)) && ((Good credit history)) ) { Discount + 5; Discount + 2; } if ( ((Cash payment)) && (!(Special offer)) && (!(Good credit history)) ) { Discount + 5; }
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Generation – Rule List 2
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if ( (!(Cash payment)) && ((Special offer)) && ((Good credit history)) ) { Discount + 10; Discount + 2; } if ( (!(Cash payment)) && ((Special offer)) && (!(Good credit history)) ) { Discount + 10; } if ( (!(Cash payment)) && (!(Special offer)) && ((Good credit history)) ) { Discount + 2; } if ( (!(Cash payment)) && (!(Special offer)) && (!(Good credit history)) ) { } }
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Generation – Rule Mask
32
{Mask = 11111111 {if ( Cash payment) Mask AND 11110000; } {if ( Special Offer) Mask AND 11001100; } {if (Good credit history) Mask AND 10101010; } {if (Mask AND 11110000) Discount + 5 ; } if (Mask AND 11001100) Discount + 10; } if (Mask AND 10101010) Discount + 2; }
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Rule masking
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• Succinct code
• Reduces repetition of condition testing
• Reduced repetition of action code
• Fast execution
• No frequency/cost weighting of rules
needed
• All conditions are evaluated
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Relevance Testing
34
AGE > 50 Y - -
CALL ADJUST_COVER Y - -
TRANSKEY LT MASTKEY - Y -
LOOKUP MASTER TRANSKEY - Y -
Some operations require dynamic masking where actions may be performed or I/O occurs
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Relevance Testing
35
AGE > 50 Y - -
COVER + 20 R - -
TRANSKEY LT MASTKEY - Y -
DISPLAY “Message” - R -
Dynamic masking again needed when Actions are inserted into condition section of Decision Table using “R”
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Decision table linkage
36
CALLs to other DTs or object library routines
CALL Credit_limit_exceeded Y ELSE
CALL Cash_payment N -
CALL Special_clearance N -
CALL ACCEPT_ORDER - X
CALL REJECT_ORDER X -
GOTO link to DT or indirect CALL
CALL Credit_limit_exceeded Y ELSE
CALL Cash_payment N -
CALL Special_clearance N -
GOTO ACCEPT_ORDER - X
CALL_I Variable_name X -
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Requirements of a DT language
• Feature rich language
• Support for multiple data types
• Unmatched data type comparison
• Good string handling/text manipulation
• Access external routines/library functions
• File, database, object and data dictionary
• Callable access from other products
• Source code maintenance, version control
• Compiled and portable execution
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Decision Tables in other products
• Uses GUI in SAP HANA Studio
• SAP Parameter/Database DTs
• Alternate use via Excel spreadsheets
• SMARTS
• OpenRules Engine
• Decision First Modeler
• Drools
• Many more …
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Usage of RPL - expertGenius
• Self compiling
• Cross compiling
• Source of Genius Suite
• Code writing and compiling 4GL and RAD
toolset
• Complete layered application suites
• Reporting – fixed logic
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Genius deployment
• Aerospace factory tracking systems
• Mobile phone billing systems
• Payroll data mining
• HR system ad-hoc querying
• Newspaper distribution system
• Stock control
• Sales order dashboard & EIS
• Web based on-line parts ordering
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CDT Callable Decision Tables
• Simple calculator
• Calculator code
• Tax formula (UK)
• Tax calculator
• Tax code
• CDT Callable access from other
languages and applications
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Future developments
• Extend range of generic database access
• Ports to new architectures
• Macro expansions for FEEL or S-FEEL
• GUI extensions
• CDT Callable access from other
languages and applications
• Cloud based compiler
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Howard Rogers Director Technical Support
Decision Tables as a
Programming tool
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Filetab
• DEcision TABle-based computer
programming language.
• Long history originating in late 1960s
• Developed by the UK National Computing
Centre (NCC)
• Originally used on ICL OS such as
GEORGE 2/3 and VME,
• Ported to a large number of others.
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Filetab
• Original architect - Tom Barnard, who developed the
program (LITA - LIst and TAbulate) for Morgan
Crucible on an ICL 1902 from 1965–1968. Original
purpose was to produce simple ad hoc reports with
a plugboard on a punched card tabulator, replaced
PLAN assembly language.
• 80 column card based parameters
• Reporting tool specifying input and output formats,
headings, sequencing and totalling.
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RapidGen Solutions
RapidGen solves tough integration problems
for OpenVMS customers
• A variety of flexible options available
– Analyse and provide ‘Customised Solutions’
– Future Proofing options with RapidGen
• In-depth Legacy expertise
• Services + Software
– OpenVMS to Linux Migration Routines
• Databases and Porting
• Data Structures migration
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What Customers Tell Us
Want to preserve, modernize or replace
• Total cost of ownership
• Risk, flexibility
…but difficult
• Bespoke or end-of-life applications
• Custom interfaces issues
• Skills shortage becoming more evident
• Application Changes not permitted
– E.g. Aerospace, Defence, Nuclear, Utilities
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Customers Want Flexibility
They Need Options
Choices
1. Update OpenVMS
– Until end of 2015
2. Modernise
– Translate data
– Translate logic
– Redefine logic in 4GL
– Redevelop
– Seamless Transition
3. Emulation Options
– Reduce Operating Costs
– Suitable for some
Want
• Proceed in stages
– Reduces risk
• Integration
– Legacy ↔ Modern
• Portability
– Future-proof
• Cost-effective Solutions
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HP Forward-looking statements
Published Jan 2014
This is a rolling (up to three year) roadmap
and is subject to change without notice.
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Example of HANA parameter DT
QUANTITY ORDER_AMOUNT DISCOUNT
<=2000 >10000 10
<=10000 5
>2000 >10000 15
<=10000 10
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Example of HANA Database DT
MANUFACTURER MODEL_CLASS QUANTITY DISCOUNT
Sprongal Handset >5 25
<=5 10
Notebook >5 15
<=5 10
Pruckman Tablet >5 15
<=5 8
Range Extender >5 10
<=5 5
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Genius Supported Platforms
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Operating System Platforms Min. Version
OpenVMS VAX 5.6
OpenVMS Alpha 6.1
OpenVMS Integrity / Itanium *
Tru64 Alpha 4.0
HP-UX HP PA 9.x
Windows Intel/AMD 32/64 2000
Linux
•Red Hat, Debian, SUSE, Ubuntu,
Fedora, Knoppix, Gentoo etc
Intel/AMD 32/64 2.6.18 kernel
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Genius Supported File Types & Databases
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OpenVMS Tru64 Windows Linux
RMS Indexed ✔ via TCP/IP via TCP/IP
ISAM ✔ ✔ ✔ ✔ Oracle RDB
•via DSRI ✔
Oracle
•via OCI ✔ ✔ ✔ ✔
DBMS-32
•Codasyl ✔
Generic ODBC
•SQL Server
•MySQL
•PostgreSQL
•…others on request
✔ ✔
Ingres
•Low-level API ✔ ✔ ✔
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• Howard Rogers
• Jolyon Cox
QUESTIONS
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Howard Rogers [email protected]
Tel: +44 (0) 1732 850081
Mob: +44 (0) 7734 962855
Providing Solutions and Options
For
OpenVMS Customers
RapidGen Offices [email protected]
Tel: +44 (0) 207 630 9291
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About RapidGen
• Integrating and modernizing legacy IT systems
for over 30 years
• Specialise in OpenVMS and Tru64
• Software is Powered by the ‘Genius’ Suite
• Our USP Unique Selling Point – Decision Tables = – Rapid Development Turnaround
– Providing Cost Effective Solutions
– Applications Future Proofing
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