▁His ▁Problem ▁Stat ement ▁Language ▁/ ▁Problem ▁Stat ement ▁Anal y zer ▁( PS L / PS A ) ▁tool ▁was ▁a ▁CASE ▁tool ▁although ▁it ▁pred ated ▁the ▁term . ▁ ▁Another ▁major ▁thread ▁emer ged ▁as ▁a ▁logical ▁extension ▁to ▁the ▁data ▁dictionary ▁of ▁a ▁database . ▁By ▁extending ▁the ▁range ▁of ▁metadata ▁held , ▁the ▁attributes ▁of ▁an ▁application ▁could ▁be ▁held ▁within ▁a ▁dictionary ▁and ▁used ▁at ▁runtime . ▁This ▁" active ▁dictionary " ▁became ▁the ▁prec ursor ▁to ▁the ▁more ▁modern ▁model - dri ven ▁engineering ▁cap ability . ▁However , ▁the ▁active ▁dictionary ▁did ▁not ▁provide ▁a ▁graph ical ▁representation ▁of ▁any ▁of ▁the ▁metadata . ▁It ▁was ▁the ▁linking ▁of ▁the ▁concept ▁of ▁a ▁dictionary ▁holding ▁anal yst s ' ▁metadata , ▁as ▁derived ▁from ▁the ▁use ▁of ▁an ▁integrated ▁set ▁of ▁techniques , ▁together ▁with ▁the ▁graph ical ▁representation ▁of ▁such ▁data ▁that ▁gave ▁rise ▁to ▁the ▁earlier ▁versions ▁of ▁CASE . ▁ ▁The ▁next ▁entr ant ▁into ▁the ▁market ▁was ▁Excel er ator ▁from ▁Index ▁Technology ▁in ▁Cambridge , ▁Mass . ▁ ▁While ▁Design A id ▁ran ▁on ▁Con ver gent ▁Techn ologies ▁and ▁later ▁B urr ough s ▁N gen ▁network ed ▁micro comput ers , ▁Index ▁launched ▁Excel er ator ▁on ▁the ▁IBM ▁PC / AT ▁platform . ▁While , ▁at ▁the ▁time ▁of ▁launch , ▁and ▁for ▁several ▁years , ▁the ▁IBM ▁platform ▁did ▁not ▁support ▁networking ▁or ▁a ▁central ized ▁database ▁as ▁did ▁the ▁Con ver gent ▁Techn ologies ▁or