Extracting UML/OCL Integrity Constraints and Derived Types from Relational Databases

© AtlanMod - [email protected]

Extracting UML/OCL Integrity Constraints andDerived Types from Relational Databases

Valerio CosentinoSalvador Martínez

{valerio.cosentino, salvador.martinez}@mines-nantes.fr

07/10/13 © AtlanMod - [email protected]

Outline

Introduction Approach overview Model Extraction Constraint Extraction Conclusion and future work


Introduction

Relational databases play a key role in most organizations

They store relevant information according to:– Schema: data structure definitions and relations– Integrity constraints (declarative, operational):

implementation of organization policies/business rules

These constraints should evolve together with the organization policies


Introduction

Discovering/understanding the business rules in a db is:– Time-consuming (querying/browsing the database) – Error-prone (manual analysis)– Tailored process (each SQL vendor offers slight

variations for the standard language) Model Driven Engineering offers:

– Homogeneous representation (schema + constraints)– Higher abstraction level (no SQL vendor specificities)– Automatation of repetitive activities (extraction of

schema and constraints)


Approach overview

Model Extraction translates tables, relations and views into UML classes and associations

Constraint Extraction focuses on inferring the OCL expressions required to complement the UML model


Model Extraction

Mappings:– Tables → classes– Views → derived classes– Columns → class's attributes– Database data types → UML data types

CHAR(n), VARCHAR2(n) → String Integer, Float, Date → Integer, Real, Date Number(precision, scale) → if precision = 0 Integer else Real

– Foreign keys → associations between classes– SQL queries → associations' cardinalities


Model Extraction

Example: human resource database


Constraint Extraction

Declarative constraints:– PRIMARY KEY– UNIQUE– NOT NULL– CHECK

Operational constraints:– Triggers: PL/SQL - SQL code automatically executed in

response to certain database events Key elements: SQL-to-OCL and PL/SQL-to-OCL

– they map SQL and PL/SQL constructs to OCL


Declarative constraints

Declarative constraints:

Example:


SQL to OCL

Projection and selection:

Example:


SQL to OCL

Join:

Example:


SQL to OCL

Group and having clause:

Example:


Triggers

Triggers are composed by:– Triggering event: SQL statement, database or user event– Trigger condition (optional): boolean expression– Triggered action: PL/SQL block (procedural and SQL code)

They can be executed: instead of, before or after performing the triggering event

Example:


PL/SQL to OCL

All triggers that embed in their action a PL/SQL statement raising an exception defined by the user are classified as business-relevant– Two ways to use user exceptions:

RAISE statement (Override an already-defined exception) RAISE APPLICATION ERROR statement

These exceptions are generally nested in conditional statements. For each exception, the conditions triggering the exception are mapped to an equivalent OCL expression.


PL/SQL to OCL

Trigger:

Example:SQL to OCL mappings


Refining OCL Constraints

UML stereotype mechanisms are used to annotate each OCL constraint extracted from a Trigger with the information of the events that apply to it (insert, update, delete)

Annotated OCL constraints can be merged together when:– they are semantically-equivalent– they are applied to different events

Example:


Conclusion and future work

MDE benefits:– Modular and generic approach– Automatic extraction of the organization policies in

databases Future work

– Test the framework on a real database application– Extend the OCL language with additional libraries for

representing calendar-based constraints– Integrate the extracted business rules with those ones

extracted from other system's components


Questions

Technology

Extracting UML/OCL Integrity Constraints and Derived Types from Relational Databases