2nd lhc computing workshop, barcelona [email protected], it/asd cern lhcc computing board an...

2nd LHC Computing Workshop, Barcelona

[email protected] , IT/ASD

CERN LHCC Computing Board

An Introduction

Jamie Shiers, IT/ASD, CERN

Reviewer Member, ODMG

March 1998

2




Introduction

What is the ODMG?

What are its goals?

Why it is relevant to HEP

March 1998

3




The ODMGThe Object Database Management Group is a consortium of object-oriented database management

system (ODBMS) vendors and interested parties working on standards to allow portability of customer software across ODBMS products

Mission Statement The mission of the Object Database Management Group

consists of four key objectives.– EVOLVE: Continue to develop the standard– PROMOTE: Raise awareness of ODMG 2.0 – EDUCATE: Explain ODMG 2.0 features and benefits– VALIDATE: Assure compliance to ODMG 2.0

March 1998

4




ODMG MembersVoting Members

– must ship, or have announced intent to ship, a compliant ODBMS

Gemstone IBEX (Itasca) Lockheed Martin (ADA-95 binding) Objectivity ODI (ObjectStore) POET Versant Vmark (UniData/O2)

Reviewer Members include CERN and others

March 1998

5




ODMG Standard Provides the only standard for object databases Implemented by numerous vendors Includes language bindings:

– C++, Java, Smalltalk, [ ADA-95 ]

Includes Object Interchange Format (OIF)– The Object Interchange Format (OIF) is a specification language

used to dump and load the current state of an object database to or from a file or set of files. OIF can be used to exchange objects between databases, seed databases, provide database documentation and drive database test suites.

March 1998

6




ODMG and Other Standards Java, C++ and Smalltalk language bindings build on

corresponding language standard OQL provides object query capability and is 90%

compatible with SQL-92 SELECT OQL is an OMG Data Query service ODMG is an OMG PDS (Persistent Data Service) protocol ODL is a superset of the OMG IDL ODMG is a superset of the OMG Common Object Model

March 1998

7




Future Enhancements To bring the OQL object model to the centre of the SQL3

standard To enhance object programming language bindings,

including the addition of a Java language binding– available as from ODMG 2.0

To define an OMG CORBA Object Manager Adapter interface for object databases

To achieve greater interoperability between ODMG compliant databases beyond schema level (ODL).

To provide dynamic access to meta-objects (schema)

March 1998

8




Object Definition Language

ODL (Object Definition Language):

The ODMG ODL is a database schema definition language

extension of the OMG Interface Definition Language (IDL).

Because it is restricted to object type definitions without

regard to the actual implementation of the methods behind

them, ODL makes it possible to describe a database

schema independent of the programming language thereby

making the schema portable between compliant databases.

March 1998

9




Object Query Language

OQL (Object Query Language):

OQL is an SQL-like declarative language that provides a

rich environment for efficient querying of database objects,

including high-level primitives for object sets and structures,

while retaining compatibility with the SQL-92 SELECT

syntax.

March 1998

10




Language Bindings ODMG’s Java, C++ and Smalltalk bindings define OMLs

(Object Manipulation Languages) that extend the ANSI standards to support manipulation of persistent objects, OQL, navigation and transactions. Because each language has its own OML, developers can work in a single language environment without separate programming and database languages.

“The programmer should perceive the binding as a single language for expressing both programming and database operations, not two languages with arbitrary boundaries between them.”

March 1998

11




ODBMS vs RDBMS

March 1998

12




ODMG vs Embedded SQL Init(); // initialise the db session

startUpdate(); // start an update transaction

// create a new database (file)

HepDatabaseRef myDb = db("MyDatabase");

// create a new container in this database

HepContainerRef cont = container("MyContainer");

if (cont == 0 )

fatal("could not find or create MyDatabase");

for (short i=0; i<1000; i++)

{

// create a new event in my container

HepRef(HepEvent) event = new(cont) HepEvent;

if (event == 0)

fatal("could not create a new event");

}

EXEC SQL WHENEVER SQLWARNING GOTO 1100

EXEC SQL LOCK TABLE FATMEN IN SHARE MODE

EXEC SQL SELECT * INTO :DBASE, :EXPER FROM FATMEN

2 WHERE DATABASE =:DBASE AND EXPERIMENT =:EXPER

STMT1 = 'LOCK TABLE GNAMES_' // EXPER(1:LEXP) // ', FILES_' //

1 EXPER(1:LEXP) // ', FXV_' // EXPER(1:LEXP) //

2 ',VOLUMES_' // EXPER(1:LEXP) // ' IN EXCLUSIVE MODE'

CMD = 'STMT1'

EXEC SQL EXECUTE IMMEDIATE :STMT1

March 1998

13




HepODBMSPrimary goals are: Minimise the dependence on given ODBMS implementation

(vendor or release), Provide a higher-level interface to ODBMS, Minimise the effort involved in porting existing applications

that require persistence.

Examples of additional functionality: Event collection classes (109 - 1011 events), Enhanced clustering, Naming, HEP Meta-Data, Calibration Database Application, ...

March 1998

14




ODMG non-goals We do not wish to produce identical ODBMS products. Our

goal is source code portability; there is a lot of room for

future innovation in a number of areas. There will be

differences between products in performance, languages

supported, functionality unique to particular market

segments (e.g., version and configuration management),

accompanying programming environments, application

construction tools, small versus large scale, multithreading,

networking, platform availability, depth of functionality,

suites of predefined type libraries, GUI builders, design

tools, and so on.

March 1998

15




Using an ODBMS

March 1998

16




ODMG & RD45 Many of RD45’s milestones have been directly related to

the ODMG:

1995: An evaluation of the suitability of ODMG's Object Definition Language for

specifying an object model describing HEP event data. Starting from such a model, the development of a prototype using commercial

ODBMSs that conform to the ODMG standard. The functionality and performance of the ODBMSs should be evaluated.

1996: Identify and analyse the impact of using an [ ODMG-compliant ] ODBMS for

event data on the Object Model, the physical organisation of the data, coding guidelines and the use of third party class libraries.

These issues have been reported on to the LC(R)B and other committees

March 1998

17




Need for a Standard Interface

A paper at HepVIS ’95 & the CMS CTP both stress: Correctness, Homogeneity, Consistency, Fault tolerance, Ease of use.

In today’s (CERNLIB) environment, many different interfaces for different types of data– (FZ,RZ,HBOOK,HEPDB,FATMEN, etc.)

One of the first discussions in RD45 revealed importance of a consistent interface– Two potential candidates: ODMG & OMG POS

March 1998

18




RD45: First Steps Evaluations of existing packages/prototypes/solutions Discussions with experts in the field Presentations by vendors

– O2, ODI (ObjectStore), Objectivity, Iona (Orbix)

Training– O2, Objectivity

Mentoring– Doug Barry, Rick Cattell, Sean Baker, Sophie Gamerman, Leon Guzenda

– Close contacts with other ‘similar’ projects

Strong support for ODMG including from Iona, who declared OMG POS as “unimplementable” POS has since been withdrawn and a new version, compatible with ODMG, is

being discussed

March 1998

19




OMG Persistent State Service PSS2 is a new OMG service. The intent was a second

generation (replacement) to the old POS (persistent object service), that has seen very little use…

PSS2 is based on a single-level approach, … simpler, better (up to date with ODMG interfaces), and better integrated with ORB products.

The idea is to take the experience ... like that with Orbix, and generalize it to a standard…

[ ODMG is still the only implemented standard in the persistent-object space ]

March 1998

20




Benefits of ODMG Membership Possibility to influence ODMG standards are somewhat

limited– would require significant extra participation, e.g. 1 week/month in

the US, to change this

Benefits in learning of ODMG’s direction long before standards are published– as book “The Object Database Standard, Morgan Kaufmann”– helps influence vendor to move to ODMG compliance in a timely

manner

Exposure to architectural details of different products Chance to meet developers Current participation ~1 meeting/year

March 1998

21




Summary

The ODMG language bindings are successful in their goal

of being a “natural extension” to the programming language

ODL (Objectivity/DB DDL) has been shown to be suitable

for describing HEP object models

ODMG-compatible ODBMS products meet HEP’s

requirements in terms of providing a consistent interface to

all types of data– histograms, calibration data, event data etc.

2nd lhc computing workshop, barcelona [email protected], it/asd cern lhcc computing board an...

Documents