Xjyuk

Do you know how to use tikz people here? It throws me an error.

Credits to @Marmot

documentclass[tikz,border=3.14mm]standalone
usepackagetikzlings
usepackagelmodern
usepackagetikzpeople
usetikzlibrarypositioning,shadows.blur,shapes.geometric,calc,fit
tikzsetdatabase/.style=cylinder,aspect=2,draw,fill,shape border rotate=90,path picture=
draw[white] let p1=($(path picture bounding box.north east)-(path picture bounding
box.south west)$) in 
foreach XX in 1,2,3 ([yshift=-XX*y1/4]path picture bounding box.north west) 
arc(180:360:x1/2 and 0.25*x1/2);

begindocument
begintikzpicture[font=tiny]
 beginscope[nodes=draw,align=center,local bounding box=Canada]
 node[database,minimum size=3em,label=[name=DB]below:DB] (db);
 node[draw=blue,anchor=north] (MT) at ([xshift=-9em]db.west) Training \ model;
 node[draw=green!60!black,above=2em of MT] (PM) Predictive \
 Model;
 path (PM.north west) + (-3em,5em) (MT) + (0,-5em);
 endscope
 draw (Canada.south west) rectangle (Canada.north east) node[below
 left]Recommendation Engine;
 path let p1=($(Canada.north)-(Canada.south)$) in 
 node[left=1em of Canada,minimum height=y1,inner ysep=0pt,draw] (Client) Client;
 bob[shift=([xshift=-5em,yshift=-3em]Client.west)]
 beginscope[thick,-latex,nodes=fill=white,align=center]
 draw (Client.71) -| (db) node[pos=0.35]
 user feedback\ (ratings, clicks, watch, browsee);
 draw[green!60!black] (db.west) -- ++(-2em,0) |- (PM) 
 node[pos=0.2]New products;
 draw[green!60!black] (PM.west) -- ++(-1em,0) |- (Client.-70) 
 node[pos=0.2]Recommended \ Products;
 draw[dashed,blue!80!black] (DB.south) -- ++ (0,-1.5em) -| (MT)
 node[pos=0.2]User history;
 draw[dashed,blue!80!black] (MT) -- (PM);
 endscope
endtikzpicture

enddocument

Because bob is not a command, but bob is a node shape. The tikzlings and tikzpeople are a bit different in this regard. (There is the possibility to use pics for the tikzlings, but in my previous answer I used another syntax which also works. Defining shapes is actually more effort than "just" defining pics or commands, you can as Rmano about it. ;-)

documentclass[tikz,border=3.14mm]standalone
usepackagetikzlings
usepackagelmodern
usepackagetikzpeople
usetikzlibrarypositioning,shadows.blur,shapes.geometric,calc,fit
tikzsetdatabase/.style=cylinder,aspect=1,draw,fill,shape border rotate=90,path picture=
draw[white] let p1=($(path picture bounding box.north east)-(path picture bounding
box.south west)$) in 
foreach XX in 1,2,3 ([yshift=-XX*y1/4]path picture bounding box.north west) 
arc(180:360:x1/2 and 0.25*x1/2);

begindocument
begintikzpicture[font=tiny]
 beginscope[nodes=draw,align=center,local bounding box=Canada]
 node[database,minimum size=3em,label=[name=DB]below:DB] (db);
 node[draw=blue,anchor=north] (MT) at ([xshift=-9em]db.west) Training \ model;
 node[draw=green!60!black,above=2em of MT] (PM) Predictive \
 Model;
 path (PM.north west) + (-3.5em,5em) (MT) + (0,-5em) (db.east) +(1em,0);
 endscope
 draw (Canada.south west) rectangle (Canada.north east) node[below
 left]Recommendation Engine;
 path let p1=($(Canada.north)-(Canada.south)$) in 
 node[left=1em of Canada,minimum height=y1,inner ysep=0pt,draw] (Client) Client;
 node[bob,left=1.2em of Client,scale=2];
 beginscope[thick,-latex,nodes=fill=white,align=center]
 draw (Client.71) -| (db) node[pos=0.3]
 user feedback\ (ratings, clicks, watch, browsee);
 draw[green!60!black] (db.west) -- ++(-2em,0) |- (PM) 
 node[pos=0.2]New\ products;
 draw[green!60!black] (PM.west) -- ++(-1em,0) |- (Client.-70) 
 node[pos=0.2]Recommended \ Products;
 draw[dashed,blue!80!black] (DB.south) -- ++ (0,-1.5em) -| (MT)
 node[pos=0.2]User history;
 draw[dashed,blue!80!black] (MT) -- (PM);
 endscope
endtikzpicture
enddocument