{
    // Declare observable x
    RooRealVar x("x","x",0,10);

    // Create two Gaussian PDFs: g1 and g2
    RooRealVar mean("mean","mean of gaussians",5,0,10);
    RooRealVar sigma1("sigma1","width of gaussians",0.5);
    RooRealVar sigma2("sigma2","width of gaussians",1);
    RooGaussian sig1("sig1","Signal component 1",x,mean,sigma1);  
    RooGaussian sig2("sig2","Signal component 2",x,mean,sigma2);  
    
    // Build Chebychev polynomial p.d.f.  
    RooRealVar a0("a0","a0",0.5,0.,1.);
    RooRealVar a1("a1","a1",-0.2,0.,1.);
    RooChebychev bkg("bkg","Background",x,RooArgSet(a0,a1));

    // Sum the signal components into a composite signal p.d.f.
    RooRealVar sig1frac("sig1frac","fraction1 in signal",0.8,0.,1.);
    RooAddPdf sig("sig","Signal",RooArgList(sig1,sig2),sig1frac);

    // Sum the composite signal and background 
    RooRealVar bkgfrac("bkgfrac","fraction of background",0.5,0.,1.);
    RooAddPdf  model("model","g1+g2+a",RooArgList(bkg,sig),bkgfrac);

    // Generate a data sample of 1000 events in x from model
    RooDataSet *data = model.generate(x,1000);

    // Create a new empty workspace
    RooWorkspace *w = new RooWorkspace("CMGWs","CMG workspace");

    // Import model, all its components and data into the workspace
    w->import(model); w->import(*data);

    // Print workspace contents
    w->Print();

    // Save the workspace into a ROOT file
    w->writeToFile("CMG_workspace.root");
  }