Download - 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
2
Outline
• Introduction
• Goals and Criteria
• Data Model
• Manipulation operations
• Algebra
• Conclusions
3
Introduction (1/5)
Cooperative work:
• Important, e.g. software development
- Multiple alternative proposals
- Selection
• Software engineering tools
4
Introduction (2/5)
Cooperative work:
• Analogous problems using DBs to model complex domains
• Incremental modeling, cooperative work
5
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
6
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
7
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)
8
Goals (1/3)
• Extending BCDM to support cooperative updates
• Propose vs accept/reject
• Alternative proposals of updates
Notice: underlined implementation
9
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
10
Criteria (3/3)
•“Minimal” extension of BCDM:– Upward compatibility (manipulation
operations)– Reducibility (algebra)
11
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
12
Data Model (2/9)
Authoring
Note: author as a data attribute
- Basically a “standard”: attribute (however, author cannot be modified)
13
Data Model (3/9)
Super user data
• Standard BCDM
14
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))
15
Data Model (5/9) insert proposals
pi(r) is a set of standard BCDM tuples
16
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
17
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
18
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)
19
Data Model (9/9) update proposals
pu(r) is a set of proposal tuples on r
Property: uniqueness of representation
20
Manipulation operations
• E.g.: propose update
***
* Notice: value equivalent proposals for the same origin are not allowed
21
Manipulation operations
• E.g.: accept update proposal
***
• Notice: the alternatives of the selected updated are not allowed
22
Manipulation Operations
“two level” check on legal operations
• 1) Proposal Time– Super: <a, vt1>– Propose_update (x | <a, vt2>)
REJECTED
• 2) Evaluation Time
23
Manipulation operations
Property 1. Upward compatibility
Moreover, if Policy 1 is adopted:
Property 2. “Semantic” upward compatibility
24
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)}
25
Algebraic operations
E.g.: natural join:
***
26
Algebraic operations
Definition: conv
***
Property
conv( OpA( pu(r) ) ) = opBCDM( conv( pu(r) ) )
* Note: underlying possible implementation
27
Conclusions
• Problem of cooperative update is important
• New problem in DB field
• BCDM extended to support:– Data model– Manipulation operations– Algebra
• Upward compatibility
• Implementation