protected override Collection<SamlAttribute> GetIssuedClaims(RequestSecurityToken RST)
{
    EndpointAddress rstAppliesTo = RST.AppliesTo;

    if (rstAppliesTo == null)
    {
        throw new InvalidOperationException("No AppliesTo EndpointAddress in RequestSecurityToken");
    }

    string bookName = rstAppliesTo.Headers.FindHeader(Constants.BookNameHeaderName, Constants.BookNameHeaderNamespace).GetValue<string>();
    if (string.IsNullOrEmpty(bookName))
        throw new FaultException("The book name was not specified in the RequestSecurityToken");

    EnsurePurchaseLimitSufficient(bookName);

    Collection<SamlAttribute> samlAttributes = new Collection<SamlAttribute>();

    foreach (ClaimSet claimSet in ServiceSecurityContext.Current.AuthorizationContext.ClaimSets)
    {
        // Copy Name claims from the incoming credentials into the set of claims to be issued.
        IEnumerable<Claim> nameClaims = claimSet.FindClaims(ClaimTypes.Name, Rights.PossessProperty);
        if (nameClaims != null)
        {
            foreach (Claim nameClaim in nameClaims)
            {
                samlAttributes.Add(new SamlAttribute(nameClaim));
            }
        }
    }
    // Add a purchase authorized claim.
    samlAttributes.Add(new SamlAttribute(new Claim(Constants.PurchaseAuthorizedClaim, bookName, Rights.PossessProperty)));
    return samlAttributes;
}