ER2XML

ER to XML Translator

Min Song, Jinho Kang

Project Advisor : Murali Mani

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Introduction– Database design process– Benefit from using XML as logical data model– Limitation of existing conceptual models

ERex (ER extended for XML) XGrammar ER2XML Translation examples Conclusion and future development

Outline

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DB design process

Phase 1 : Conceptual design phase Phase 2 : Logical design phase Phase 3 : Physical translation phase

Our focus

Automatic translation from conceptual model to logical model

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XML : Promising logical data model

Benefit 1 : NecessityLingua franca for information exchange over the web

Benefit 2 : CapabilityWell suited for present day application with features like

1) Union types

Example : Entity Person can have City and State information OR ZIP information, but not both.

2) Ordered relationship

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Limitation of existing conceptual models

Existing conceptual models

1. ER (Entity Relationship) Model

2. UML (Unified Modeling Language)

3. ORM (Object Roll Modeling)

All of these models do not have modeling capabilities to represent union types.

Disables main feature provided by XML.

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Extensions to the ER Model

Given features of ER1. ER models : Representative of real world database

application.

2. Nomalization – No redundancy

Extended features to ER1. Structural specification

- Categories

2. Constraint specification

- Coverage constraints (Total & Exclusive)

- Order constraints

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Categories in EReX

Relationship type similar to ISA relationship type

PersonCity and PersonZip are category entities of an entity Person

Each category entity can have its own key attribute

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Coverage Constraints

Coverage constraints are specified on entity types or roles.

Total coverage constraint : PersonCity U PersonZip = PersonInterpretation : All instances of Pers

onCity and all instances of Personzip sums up to all instances of Person

Exclusive coverage constraint : PersonCity ∩ PersonZip = PersonInterpretation : There is no instance

in Person that has city, state and zip all together.

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XGrammar Define

A schema in XGrammar- Denoted by a 6-tuple G = (N,E,A,S,P, ∑)- N is a finite set of non-terminal symbols- E is a finite set of element names- A is a finite set of attribute names- S is set of start symbols- P is set of production rules of the form X → x

(RE)- ∑ is the set of constraints.

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ER2XML

Developed in Java which provides platform independent environment.

Provides easy way to generate correct schema from complex EReX diagrams.

Fully adapts all features of XGrammar. Displays intermediate translation steps

and results to back trace the problem

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ER2XML - Features

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ER2XML – Coverage Constraints

• User can create total or exclusive coverage constraints by combining multiple entities or roles.

• Verification of the constraints will be shown on the command screen.

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ER2XML – Translation

Brief translation procedure1. Initialization of symbols

- N, E, A, S, P and ∑2. Translation of relationship types3. Removal of unnecessary symbols4. Capture exclusive coverage constraints5. Capture total coverage constraints6. Distinguish ROOTS among symbols

• Some coverage constraints might not be captured in XGrammar.

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ER2XML

Schema generated by ER2XML is consistent with example schema.

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ER2XML – Complex EReX

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ER2XML – Complex EReX

N = {Root, Person, Bank, Checking, Savings, Loan company, Card company, Account_info, Credit_history, Banks with, Apply_for, Rated, Request} E = {root, person, bank, checking, savings, loan company, card company, credit_history, account_info, banks with, apply_for, rated, request} A = {ssn, city, state, zip, pho-number, routing_number, BID, CH-acc, ch-bal, SV-acc, sv-bal, loan-number, LID, CID, C-acc, balance, limit, BRef, decision, LRef, points, CRef, LR

ef} S = {Root} P = {Root -> root(Person*, Bank*, Loan company*) Person -> person(@ssn,Banks with[*], Apply_for[+], Rated[*], ((@street,@city,@state,@zip) + @pho-number),(Checking[+] + Savings[+])) Bank -> bank(@routing_number,@BID,Request[+]) Checking -> checking(@CH-acc,@ch-bal) Savings -> savings(@SV-acc,@sv-bal) Loan company -> loan company(@loan-number,@LID,Card company[1], (Credit_history[+] + Account_info[+])) Card company -> card company(@CID) Account_info -> account_info(@C-acc,@balance) Credit_history -> credit_history(@limit) Banks with -> banks with(@BRef) Apply_for -> apply_for(@decision,@LRef) Rated -> rated(@points,@CRef) Request -> request(@LRef) } IDREF constarints: {BRef::IDREF~(Bank) LRef::IDREF~(loan company) CRef::IDREF~(card company) LRef::IDREF~(loan company) } Key Constraints: {key(Account_info)=(@C-acc) key(Credit_history)=(@limit) key(Person)=(@ssn) key(Checking)=(@CH-acc) key(Loan company)=(@loan-number) key(Bank)=(@routing_number) key(Banks with)=(parent::person/@ssn,BRef) key(Apply_for)=(parent::person/@ssn,LRef) key(Rated)=(parent::person/@ssn,CRef) key(Request)=(parent::bank/@routing_number,LRef) }

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Conclusion Future Works

Any EReX Diagram can be translated into XML schema with its maximum expressiveness using ER2XML.

Some coverage constraints might not be captured by XGrammar and ER2XML.

It is guaranteed that resulting schema has no redundancy as long as EReX has no redundancy.

More simplified and enhanced GUI needs to be developed.

“Generate XML” will be a big plus to current ER2XML.

More insightful comments and reasoning for each translation step will make ER2XML a great tool to learn EReX.

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References

EReX: A Conceptual Model for XML, M. Mani

Constraint Specification for XML: A Closer Look (Late Breaking News), M. Mani

Data Modeling using XML Schemas, M. Mani.