diff --git a/NAMESPACE b/NAMESPACE
index 0dcca9b..591810e 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -12,6 +12,7 @@ export(getProvenance)
 export(getUUID)
 export(importM.COSMIC)
 export(importNet.STRING)
+export(isHGNCsymbol)
 export(logEvent)
 export(logFileName)
 export(logMessage)
diff --git a/R/aaa.R b/R/aaa.R
new file mode 100644
index 0000000..00344a5
--- /dev/null
+++ b/R/aaa.R
@@ -0,0 +1,30 @@
+# fastCheckFactory.R
+#
+# Utility function to create closures for ID validation
+
+.fastCheckFactory <- function(symbols) {
+    # Creates a closure to be used to validate whether elements of a
+    #   character vector are present in the "symbols" data frame.
+    # Parameters:
+    #     symbols: a one column dataframe
+    # Value:
+    #     fCheck: a closure
+
+    symbols$symbol[1] # force access
+
+    fCheck <- function(x) {
+        # Checks whether elements of x are present in the "symbols" data
+        # frame which was loaded into this closure's environment.
+        #
+        # Returns a vector of logicals of the same length as x
+        if (missing(x) || length(x) == 0) { return(logical()) }
+
+        return(!is.na(fastmatch::fmatch(toupper(as.character(x)),
+                                        symbols$symbol)))
+
+    }
+
+    return(fCheck)
+}
+
+# [END]
diff --git a/R/isHGNCsymbol.R b/R/isHGNCsymbol.R
new file mode 100644
index 0000000..cc787d5
--- /dev/null
+++ b/R/isHGNCsymbol.R
@@ -0,0 +1,54 @@
+#' isHGNCsymbol.R
+#'
+#' Check whether gene symbols given are valid HGNC gene symbols.
+#'
+#' \code{isHGNCsymbol} Checks whether the elements of the input vector are
+#'     valid HGNC gene symbols (case insensitive) by comparing to a subset
+#'     of existing gene symbols.
+#'
+#' The subset of symbols used here contains only approved gene
+#'     symbols of the following locus types:
+#'   * gene with protein product
+#'   * immunoglobulin gene
+#'   * protocadherin
+#'   * T-cell receptor gene
+#'   * RNA: long non-coding, micro, ribosomal, transfer, small nuclear
+#'          and nucleolar, Y and vault
+#'   * endogenous retrovirus
+#'
+#' This function is a closure that contains the HGNC symbol table in its environment. It is produced as part of the .onLoad() tasks. The supporting table is stored in extdata/HGNCsymbols.RDS. The script that was used to generate this table is in scripts/generateHGNCtable.R.
+#'
+#' Checking is done in a case-insensitive manner.
+#'
+#' @param x A character vector
+#' @return A vector of logicals of length x that contains TRUE for every
+#'           element that is present in the HGNC symbol table and FALSE
+#'           for all others.
+#'
+#' @examples
+#' isHGNCsymbol()                                   # logical()
+#' isHGNCsymbol(NULL)                               # logical()
+#' isHGNCsymbol(0)                                  # FALSE
+#' isHGNCsymbol("A2M")                              # TRUE
+#' isHGNCsymbol(c("123", "234"))                    # vectorized
+#' isHGNCsymbol(c("A1BG", "a1bg", "a1Bg", "A1bG"))  # case insensitive
+#' x <- c(NA, "A1CF", NULL, "a1bg")                 # length preserving:
+#' length(x)                                        #    3
+#' isHGNCsymbol(x)                                  #    FALSE, TRUE, TRUE
+#'
+#' @export
+
+isHGNCsymbol <- function(x) {
+    stop("This function must be overwritten by a closure factory in .onLoad()")
+}
+
+tmp <- readRDS(system.file("extdata",
+                           "HGNCsymbols.RDS",
+                           package="rete"))
+
+isHGNCsymbol <- .fastCheckFactory(tmp)
+
+rm(tmp)
+
+
+# [END]
diff --git a/inst/extdata/HGNCsymbols.RDS b/inst/extdata/HGNCsymbols.RDS
new file mode 100644
index 0000000..c775440
Binary files /dev/null and b/inst/extdata/HGNCsymbols.RDS differ
diff --git a/inst/scripts/generateHGNCHash.R b/inst/scripts/generateHGNCHash.R
deleted file mode 100644
index aa00c12..0000000
--- a/inst/scripts/generateHGNCHash.R
+++ /dev/null
@@ -1,59 +0,0 @@
-# generateHGNCHash.R
-
-#' Generates a data frame containing all valid HGNC gene symbols, calls fmatch
-#' on the data frame so it will create a hash of the data frame to be used by
-#' checkGeneSymbols.R.
-#'
-#' @param fURL The URL to the file containing valid HGNC gene symbols.
-#'
-#' @seealso \code{\link{isGeneSymbol}} is used to check if a gene symbol is a
-#' valid HGNC gene symbol that is contained in inst/extdata/HGNCSymbols.rds.
-
-library(fastmatch)
-
-# Open the connection/file.
-## Change fURL to be the URL of the file containing HGNC gene symbols.
-## The file is assumed to contain the symbol, status and locus group of the gene.
-fURL <- "http://www.genenames.org/cgi-bin/download?col=gd_app_sym&col=gd_status&col=gd_locus_type&col=gd_locus_group&status=Approved&status=Entry+Withdrawn&status_opt=2&where=&order_by=gd_app_sym_sort&format=text&limit=&hgnc_dbtag=on&submit=submit"
-HGNCFile <- url(fURL, open = "r")
-
-# Read the header and vertorize.
-header <- readLines(HGNCFile, n = 1)
-headerVector <- unlist(strsplit(header, "\t"))
-
-# Find the index of the columns that contain the gene symbol, status, and locus
-# group of the genes.
-symbolCol <- which(headerVector == "Approved Symbol")
-statusCol <- which(headerVector == "Status")
-locusCol <- which(headerVector == "Locus Group")
-
-# vectors containing the (important) statuses and locus groups of interest.
-impStatuses <- c("Approved")
-impLocusGroups <- c("protein-coding gene", "other", "phenotype")
-
-# Read line by line.
-geneSymbols <- c()
-while (length(entry <- readLines(HGNCFile, n = 1)) > 0) {
-    entryVector <- strsplit(entry, "\t")
-
-    # Check the status and locus group of the gene.
-    status <- entryVector[[1]][statusCol]
-    locusGroup <- entryVector[[1]][locusCol]
-    if ((status %in% impStatuses) && (locusGroup %in% impLocusGroups)){
-        # append the current gene symbol to the list of valid gene symbols.
-        geneSymbols <- append(geneSymbols, entryVector[[1]][symbolCol])
-    }
-
-}
-
-close(HGNCFile)
-
-# Create a data frame with a single column containing the gene symbols.
-geneNames <- data.frame(
-    Gene_Symbol = geneSymbols,
-    stringsAsFactors = FALSE)
-
-# Call fmatch, so that it will create a hash of the data frame.
-fmatch("1", geneNames)
-
-# [END]
diff --git a/inst/scripts/generateHGNCtable.R b/inst/scripts/generateHGNCtable.R
new file mode 100644
index 0000000..409aefb
--- /dev/null
+++ b/inst/scripts/generateHGNCtable.R
@@ -0,0 +1,64 @@
+# generateHGNCtable.R
+
+# Generates a data frame containing all valid HGNC gene symbols, calls fmatch
+# on the data frame so it will create a hash of the data frame to be used by
+# .fastCheckFactory() to build a validator closure for HGNC symbols.
+#
+
+# Define request for the HGNC custom download CGI interface. Download gene
+# symbols and locus types only.
+HGNC_URL <- paste0("http://www.genenames.org/cgi-bin/download?",
+                   "col=gd_app_sym&col=gd_locus_type",
+                   "&status=Approved&status_opt=2",
+                   "&where=&order_by=gd_app_sym_sort",
+                   "&format=text&limit=&submit=submit")
+
+HGNCtable <- readr::read_delim(HGNC_URL, delim = "\t")
+
+# Whitelist for Locus Type to be included. We  restrict the locus types
+# to those which we consider interpreatble in the context of cancer gene
+# network analysis.
+#
+# cat(sprintf("\"%s\",\n", unique(HGNCtable$`Locus Type`)))
+
+whitelistLT <- c("gene with protein product",
+                 "RNA, long non-coding",
+                 # "pseudogene",
+                 # "virus integration site",
+                 # "readthrough",
+                 # "phenotype only",
+                 # "unknown",
+                 # "region",
+                 "endogenous retrovirus",
+                 # "fragile site",
+                 "immunoglobulin gene",
+                 # "immunoglobulin pseudogene",
+                 # "transposable element",
+                 "RNA, micro",
+                 "RNA, ribosomal",
+                 "RNA, transfer",
+                 # "complex locus constituent",
+                 "protocadherin",
+                 # "RNA, cluster",
+                 # "RNA, misc",
+                 "RNA, small nuclear",
+                 # "RNA, small cytoplasmic",
+                 "RNA, small nucleolar",
+                 "RNA, Y",
+                 "T-cell receptor gene",
+                 # "T-cell receptor pseudogene",
+                 "RNA, vault")
+
+# Create a data frame with a single column containing the gene symbols.
+HGNCsymbols <- data.frame(symbol =
+        HGNCtable$`Approved Symbol`[HGNCtable$`Locus Type` %in% whitelistLT],
+                          stringsAsFactors = FALSE)
+
+# Call fmatch, so that it will attach a hash to the data frame.
+fastmatch::fmatch("1", HGNCsymbols$symbol)
+
+# save as RDS
+# saveRDS(HGNCsymbols, file = "inst/extdata/HGNCsymbols.RDS")
+
+
+# [END]
diff --git a/man/isHGNCsymbol.Rd b/man/isHGNCsymbol.Rd
new file mode 100644
index 0000000..76e9497
--- /dev/null
+++ b/man/isHGNCsymbol.Rd
@@ -0,0 +1,50 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/isHGNCsymbol.R
+\name{isHGNCsymbol}
+\alias{isHGNCsymbol}
+\title{isHGNCsymbol.R}
+\usage{
+isHGNCsymbol(x)
+}
+\arguments{
+\item{x}{A character vector}
+}
+\value{
+A vector of logicals of length x that contains TRUE for every
+          element that is present in the HGNC symbol table and FALSE
+          for all others.
+}
+\description{
+Check whether gene symbols given are valid HGNC gene symbols.
+}
+\details{
+\code{isHGNCsymbol} Checks whether the elements of the input vector are
+    valid HGNC gene symbols (case insensitive) by comparing to a subset
+    of existing gene symbols.
+
+The subset of symbols used here contains only approved gene
+    symbols of the following locus types:
+  * gene with protein product
+  * immunoglobulin gene
+  * protocadherin
+  * T-cell receptor gene
+  * RNA: long non-coding, micro, ribosomal, transfer, small nuclear
+         and nucleolar, Y and vault
+  * endogenous retrovirus
+
+This function is a closure that contains the HGNC symbol table in its environment. It is produced as part of the .onLoad() tasks. The supporting table is stored in extdata/HGNCsymbols.RDS. The script that was used to generate this table is in scripts/generateHGNCtable.R.
+
+Checking is done in a case-insensitive manner.
+}
+\examples{
+isHGNCsymbol()                                   # logical()
+isHGNCsymbol(NULL)                               # logical()
+isHGNCsymbol(0)                                  # FALSE
+isHGNCsymbol("A2M")                              # TRUE
+isHGNCsymbol(c("123", "234"))                    # vectorized
+isHGNCsymbol(c("A1BG", "a1bg", "a1Bg", "A1bG"))  # case insensitive
+x <- c(NA, "A1CF", NULL, "a1bg")                 # length preserving:
+length(x)                                        #    3
+isHGNCsymbol(x)                                  #    FALSE, TRUE, TRUE
+
+}
diff --git a/tests/testthat/testIsHGNCsymbol.R b/tests/testthat/testIsHGNCsymbol.R
new file mode 100644
index 0000000..2d7768c
--- /dev/null
+++ b/tests/testthat/testIsHGNCsymbol.R
@@ -0,0 +1,19 @@
+# testIsHGNCsymbol.R
+
+context("test the closure isHGNCsymbol()")
+
+test_that("expected input is correctly handled", {
+    expect_equal(isHGNCsymbol(), logical())
+    expect_equal(isHGNCsymbol(NULL), logical())
+    expect_false(isHGNCsymbol(0))
+    expect_true(isHGNCsymbol("A1BG"))                    # First in table
+    expect_true(isHGNCsymbol("a1bg"))                    # Case insensitive
+    expect_true(isHGNCsymbol("ZZZ3"))                    # Last in table
+    expect_equal(isHGNCsymbol(c(NA, "A1CF", NULL, "a2m")), c(FALSE, TRUE, TRUE))
+})
+
+test_that("unexpected input does not lead to output", {
+    expect_error(isHGNCsymbol(mean), "cannot coerce")
+})
+
+# [END]