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 How we can verify the correctness of database systems with triggers in early design phase?.  Our contribution is building a tool called S2B which can automatic translate form databas

DEVELOPING A TOOL TO VERIFY TRIGGERS IN DBMS

1 Supervisor : Assoc Prof Dr Truong Ninh Thuan

Co-supervisor : MSc Le Hong Anh Student : Dang Minh Dung

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Motivation 3

No table employee yet.

Some SQL statements are only

checked when they execute

 How we can verify the

correctness of database systems

with triggers in early design phase? Infinite loop

Example 1

Example 2

 In a previous work [1], a new method was introduced by using Event-B formal method to solve above issue

 Our contribution is building a tool (called S2B) which can

automatic translate form database systems to event-b models and partly supports modelling process with the Rodin platform 4

[1] Hong Anh Le, and Ninh Thuan Truong "Modeling and verifying DML triggers using event-B." Intelligent Information and

Database Systems Springer Berlin Heidelberg, 2013 539-548

Database systems

 ECA (Event – Condition – Action) form

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Actions

Condition

Event

TRIGGER <trigger_name> <event>

WHEN <conditions> BEGIN

<actions>

END;

Generalize

Event-B is a formal method for system-level modelling and analysis.

Key features:

• using set theory as modelling notation

• using refinement to represent systems at different level

• Using mathematical proof to verify consistency

 Context

A context describes the static part of a Event-B model.

A machine describes the dynamic behaviour of a Event-B model.

o Event

Event describe when and how machine state changes over the time Event also has the form of an EAC.

The Rodin Platform is an Eclipse-based IDE for Event-B.

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S2B Tool

event-b model.

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S2B tool architecture

Database Adapter

schema.

E:\SQL-to-EventB\res\test\db\demo.db

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SELECT sql FROM

(SELECT * FROM sqlite_master UNION ALL

SELECT * FROM sqlite_temp_master)

WHERE type!='meta'

ORDER BY tbl_name, type DESC, name

SQL Extractor

 Functionality: eliminate redundant information and

transform schema into a standard form

 2 steps:

o Parsing SQL statements

o Normalizing database models

 Step 1: Parsing SQL statements

o Using ANTLR library.

o Define SQLite grammar then ANTLR generate lexer and parser

o Output: Abstract Syntax Tree (AST)

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Abstract Syntax Tree

SQL Extractor

o Reasons for normalizing database models

 AST is sequential access

 Exists opposite statements as CREATE, ALTER, DROP in schema

 Unnecessary statements as DML statements (INSERT, UPDATE, DELETE)

 We want to create a unified format across DBMS schema.

o Use visitor design pattern to travel AST

 Extend default visitor.

 Use symbol table to manager identifiers.

o Output: database models – a unified form of schema

o After SQL extractor module, we can detect some compilation errors…

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S2B Translator

event-b model.

 Base on bellow translation rules[1]:

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Database definitions Event-B concepts Rule 1 𝑑𝑏 = 𝑇, 𝐶, 𝐺 𝑑𝑏𝐶𝑜𝑛𝑡𝑒𝑥𝑡, 𝑑𝑏𝑀𝑎𝑐ℎ𝑖𝑛𝑒

Rule 2 Table 𝑡 ∈ 𝑇 𝑇𝑎𝑏𝑙𝑒 = 𝑇𝑦𝑝𝑒1 × 𝑇𝑦𝑝𝑒2 × ⋯ × 𝑇𝑦𝑝𝑒𝑛

Rule 3 Primary key constraint Invariant 𝑝𝑘: 𝑑𝑜𝑚(Type1 × ⋯ × 𝑇𝑦𝑝𝑒𝑖) ⤖

𝑟𝑎𝑛(Typei+1× ⋯ × 𝑇𝑦𝑝𝑒𝑛)

Rule 4 Constraint 𝑐 ∈ 𝐶 Invariant 𝑖

Rule 5 Trigger 𝑔 ∈ 𝐺 Event 𝑒

[1] Hong Anh Le, and Ninh Thuan Truong "Modeling and verifying DML triggers using event-B." Intelligent Information and Database Systems Springer Berlin Heidelberg, 2013 539-548

S2B Translator 12

MACHINE dbMachine

SEES dbContext

VARIABLES

t1_rec t2_rec t1_pk t2_pk

INVARIANTS

inv1 t1_rec ∈ P(table1) inv2 t2_rec ∈ P(table2) inv3 t1_pk ∈ TYPE1 ⤖ TYPE2

inv4 t1_pk ∈ TYPE3 ⤖ TYPE4

inv5 I

EVENTS

Event G1

. Event G2

.

END

A part of Event-B specification of database system

S2B Translator

 Trigger and event both have the form of an ECA (Event-Condition-Action)

 A trigger is translated to an Event-B event:

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TRIGGER <trigger_name>

<event>

WHEN <conditions>

BEGIN

<actions>

END;

EVENT <event_name>

WHEN

<event>

<conditions>

THEN

<actions>

END

S2B Translator

 Translation of trigger actions:

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SQL EVENT-B

INSERT INTO T

VALUES (value1, value2, … valuen)

ANY r

WHEN r ∈ T ∧ e ∧ c

THEN T := T ∪ r

END

DELETE FROM T

WHERE (column1 = some_value)

ANY v

WHEN v ∈ TYPE 1 ∧ e ∧ c

THEN T := {v} ⩤ T

END

UPDATE T

SET column1 = value1,

column2 = value2,…

WHERE (column1 = some_value)

ANY u

WHEN u ∈ T ∧ e ∧ c

THEN T := T ◁ u

END

⩤ : is domain subtraction operator ◁ : is relational override operator

S2B Translator

 In order to

• decouple translation implementations form database model

• Create a common API for all database elements

We apply visitor design pattern.

 Translation rules are implemented directly

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// S2BTranslator.java

rodinPrj = new RodinProject (database.getName());

preTranslate();

for ( Table tbl : database.getTables()) { translate(tbl);

}

translate(trg);

} postTranslate();

}

}

}

S2B Translator

 Translating algorithm

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Translate each table Translate each trigger

Implementation of table translation

Implementation of trigger translation

Event-B Builder

 Functionality: export event-b models into a Rodin project

 Rodin files are XML-base files

 Using a template engine call StringTemplate to help

generating Rodin files

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 Experiments

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S2B tool GUIParse Tree Inspector

Generated Event-B project after imported into Rodin

Packages in S2B tool

Conclusion and future works

o First step building successfully S2B tool

o Partly support modelling database systems

o Expends translations rule

o Decouple rules into separated files

o Support other DBMSs

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Thanks for listening.

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