Extending BCDM to support cooperative work

Extending BCDM to support cooperative work Paolo Terenziani, Alessio Bottrighi, Stefania Montani Dipartimento di Informatica, Univ. Piemonte Orientale, Alessandria, Italy Luca Anselma, Dipartimento di Informatica, Univ. Torino, Italy

Outline • Introduction • Goals and Criteria • Data Model • Manipulation operations • Algebra • Conclusions

Introduction (1/5) Cooperative work: • Important, e.g. software development - Multiple alternative proposals - Selection • Software engineering tools

Introduction (2/5) Cooperative work: • Analogous problems using DBs to model complex domains • Incremental modeling, cooperative work

Introduction (3/5) The case of clinical guidelines: • General guideline proposed by a standardization committee • Proposals of update • Local contextualization • New therapies • Evaluation of proposals * Guideline to be stored in a DB

Introduction (4/5)Open issues Augmenting DB approaches to support cooperative work, i.e.: • Distinction between proposals and acceptance/rejection • History of the evolution of the proposals • Alternative proposals * Notice: usual semantics of (relational) DBs, conjunction of tuples

Introduction (5/5)Context • Both VT and TT should be supported • “Consensus” approach (TSQL2) with a high-level semantics (BCDM) • BCDM supports several TDB implementations (not only TSQL2)

Goals (1/3) • Extending BCDM to support cooperative updates • Propose vs accept/reject • Alternative proposals of updates Notice: underlined implementation

Criteria (2/3) • Under-constrained policy: • Super user vs user • Super user operations:standard + accept/reject proposals • User operations: • delete (not proposals) • Insert • Update (chains allowed) * Notice: easy to specializeE.g.: policy 1: super users can only accept/reject

Criteria (3/3) • “Minimal” extension of BCDM: • Upward compatibility (manipulation operations) • Reducibility (algebra)

Data Model (1/9) Two data levels needed: • Super users (accepted) data • User proposals * Notice: proposals need to be maintained and affect super-user data only if/when accepted

Data Model (2/9) Authoring Note: author as a data attribute - Basically a “standard”: attribute (however, author cannot be modified)

Data Model (3/9) Super user data • Standard BCDM

Data Model (4/9)user proposals For each super-user relation r: • pi(r): set of insert proposals in r • pd(r): set of proposals of deletion of tuples in r • pu(r): set of updates of tuples (in r, pi(r), pu(r))

Data Model (5/9)insert proposals pi(r) is a set of standard BCDM tuples

Data Model (6/9)delete proposals pd(r) is a set of standard transaction-time tuples * Notice: no value-equivalent data in r VT not needed

Data Model (7/9)update proposals Update involves: • An origin tuple to be updated (time not needed) • A new temporal tuple (standard BCDM tuple) * Notice: multiple update proposals involving the same origin are in alternative

Data Model (8/9)update proposals Definition: proposal tuple • An origin • A non empty set of (bi)temporal tuples Interpretation: disjunctive set of alternative proposals (each one is a BCDM tuple)

Data Model (9/9)update proposals pu(r) is a set of proposal tuples on r Property: uniqueness of representation

Manipulation operations • E.g.: propose update *** * Notice: value equivalent proposals for the same origin are not allowed

Manipulation operations • E.g.: accept update proposal *** • Notice: the alternatives of the selected updated are not allowed

Manipulation Operations “two level” check on legal operations • 1) Proposal Time • Super: <a, vt1> • Propose_update (x | <a, vt2>) REJECTED • 2) Evaluation Time

Manipulation operations Property 1. Upward compatibility Moreover, if Policy 1 is adopted: Property 2. “Semantic” upward compatibility

Algebraic operations • Standard BCDM algebraic operations for super-user and for pi and pd • Conversion operations on pu: origin(pu(r)) = { o \ <o, {a1,…, an}>  pu(r)} alternative(pu(r)) = Schema(r)BCDM({{a1,…, an} \ <o, {a1,…, an}>  pu(r)}

Algebraic operations E.g.: natural join: ***

Algebraic operations Definition: conv *** Property conv( OpA( pu(r) ) ) = opBCDM( conv( pu(r) ) ) * Note: underlying possible implementation

Conclusions • Problem of cooperative update is important • New problem in DB field • BCDM extended to support: • Data model • Manipulation operations • Algebra • Upward compatibility • Implementation

Extending BCDM to support cooperative work