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Computers, Computer Science Produced during Physical Design, it shows how the logical processes that access the LDM are mapped onto the physical processes that access the physical database. If there is a one-to-one correspondence between logical and physical accesses, then there is no need for a PDI; if the two do not match exactly, the PDI shows how the mismatches can be resolved in terms of physical access. If a non-procedural language such as SQL is used at the site, the PDI can be implemented in just one or two lines. The aim of the PDI is to allow the designer to implement the Logical Update and Inquiry Processes as programs, independently of the physical database structure.
Ríomhairí, Ríomheolaíocht Cuirtear é seo ar fáil i rith an Deartha Fhisiciúil agus taispeánann sé conas a mhapáiltear na próisis loighciúla a bhfuil rochtain acu ar an LDM anuas ar na próisis fhisiciúla a bhfuil rochtain acu ar an mbunachar sonraí fisiciúil. Má tá comhfhreagairt aon le haon ann idir rochtainí loighciúla agus rochtainí fisiciúla, ansin níl aon ghá le PDI; mura bhfuil an dá cheann in oiriúint iomlán dá chéile, taispeánann an PDI conas is féidir na mí-oiriúintí a réiteach i dtéarmaí na rochtana fisiciúla. Má tá teanga neamhghnásúil ar nós SQL in úsáid ar an láithreán, ní féidir an PDI a chur i ngníomh ach i líne amháin nó dhó, ar a mhéid. Is í aidhm an PDI ligean don dearthóir an Nuashonrú Loighciúil agus na Próisis Fiosraithe a chur i ngníomh mar fheidhmchláir, go neamhspleách ar struchtúr fisiciúil an bhunachair shonraí.